Merge branch 'i2c/for-current-fixed' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-bionic-kernel.git] / kernel / bpf / verifier.c

/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 * Copyright (c) 2016 Facebook
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/bpf_verifier.h>
#include <linux/filter.h>
#include <net/netlink.h>
#include <linux/file.h>
#include <linux/vmalloc.h>
#include <linux/stringify.h>

#include "disasm.h"

static const struct bpf_verifier_ops * const bpf_verifier_ops[] = {
#define BPF_PROG_TYPE(_id, _name) \
        [_id] = & _name ## _verifier_ops,
#define BPF_MAP_TYPE(_id, _ops)
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
#undef BPF_MAP_TYPE
};

/* bpf_check() is a static code analyzer that walks eBPF program
 * instruction by instruction and updates register/stack state.
 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
 *
 * The first pass is depth-first-search to check that the program is a DAG.
 * It rejects the following programs:
 * - larger than BPF_MAXINSNS insns
 * - if loop is present (detected via back-edge)
 * - unreachable insns exist (shouldn't be a forest. program = one function)
 * - out of bounds or malformed jumps
 * The second pass is all possible path descent from the 1st insn.
 * Since it's analyzing all pathes through the program, the length of the
 * analysis is limited to 64k insn, which may be hit even if total number of
 * insn is less then 4K, but there are too many branches that change stack/regs.
 * Number of 'branches to be analyzed' is limited to 1k
 *
 * On entry to each instruction, each register has a type, and the instruction
 * changes the types of the registers depending on instruction semantics.
 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
 * copied to R1.
 *
 * All registers are 64-bit.
 * R0 - return register
 * R1-R5 argument passing registers
 * R6-R9 callee saved registers
 * R10 - frame pointer read-only
 *
 * At the start of BPF program the register R1 contains a pointer to bpf_context
 * and has type PTR_TO_CTX.
 *
 * Verifier tracks arithmetic operations on pointers in case:
 *    BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
 *    BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
 * 1st insn copies R10 (which has FRAME_PTR) type into R1
 * and 2nd arithmetic instruction is pattern matched to recognize
 * that it wants to construct a pointer to some element within stack.
 * So after 2nd insn, the register R1 has type PTR_TO_STACK
 * (and -20 constant is saved for further stack bounds checking).
 * Meaning that this reg is a pointer to stack plus known immediate constant.
 *
 * Most of the time the registers have SCALAR_VALUE type, which
 * means the register has some value, but it's not a valid pointer.
 * (like pointer plus pointer becomes SCALAR_VALUE type)
 *
 * When verifier sees load or store instructions the type of base register
 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, PTR_TO_STACK. These are three pointer
 * types recognized by check_mem_access() function.
 *
 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
 * and the range of [ptr, ptr + map's value_size) is accessible.
 *
 * registers used to pass values to function calls are checked against
 * function argument constraints.
 *
 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
 * It means that the register type passed to this function must be
 * PTR_TO_STACK and it will be used inside the function as
 * 'pointer to map element key'
 *
 * For example the argument constraints for bpf_map_lookup_elem():
 *   .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
 *   .arg1_type = ARG_CONST_MAP_PTR,
 *   .arg2_type = ARG_PTR_TO_MAP_KEY,
 *
 * ret_type says that this function returns 'pointer to map elem value or null'
 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
 * 2nd argument should be a pointer to stack, which will be used inside
 * the helper function as a pointer to map element key.
 *
 * On the kernel side the helper function looks like:
 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 * {
 *    struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
 *    void *key = (void *) (unsigned long) r2;
 *    void *value;
 *
 *    here kernel can access 'key' and 'map' pointers safely, knowing that
 *    [key, key + map->key_size) bytes are valid and were initialized on
 *    the stack of eBPF program.
 * }
 *
 * Corresponding eBPF program may look like:
 *    BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),  // after this insn R2 type is FRAME_PTR
 *    BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
 *    BPF_LD_MAP_FD(BPF_REG_1, map_fd),      // after this insn R1 type is CONST_PTR_TO_MAP
 *    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
 * here verifier looks at prototype of map_lookup_elem() and sees:
 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
 *
 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
 * and were initialized prior to this call.
 * If it's ok, then verifier allows this BPF_CALL insn and looks at
 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
 * returns ether pointer to map value or NULL.
 *
 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
 * insn, the register holding that pointer in the true branch changes state to
 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
 * branch. See check_cond_jmp_op().
 *
 * After the call R0 is set to return type of the function and registers R1-R5
 * are set to NOT_INIT to indicate that they are no longer readable.
 */

/* verifier_state + insn_idx are pushed to stack when branch is encountered */
struct bpf_verifier_stack_elem {
        /* verifer state is 'st'
         * before processing instruction 'insn_idx'
         * and after processing instruction 'prev_insn_idx'
         */
        struct bpf_verifier_state st;
        int insn_idx;
        int prev_insn_idx;
        struct bpf_verifier_stack_elem *next;
};

#define BPF_COMPLEXITY_LIMIT_INSNS      131072
#define BPF_COMPLEXITY_LIMIT_STACK      1024

#define BPF_MAP_PTR_POISON ((void *)0xeB9F + POISON_POINTER_DELTA)

struct bpf_call_arg_meta {
        struct bpf_map *map_ptr;
        bool raw_mode;
        bool pkt_access;
        int regno;
        int access_size;
};

static DEFINE_MUTEX(bpf_verifier_lock);

/* log_level controls verbosity level of eBPF verifier.
 * verbose() is used to dump the verification trace to the log, so the user
 * can figure out what's wrong with the program
 */
static __printf(2, 3) void verbose(struct bpf_verifier_env *env,
                                   const char *fmt, ...)
{
        struct bpf_verifer_log *log = &env->log;
        unsigned int n;
        va_list args;

        if (!log->level || !log->ubuf || bpf_verifier_log_full(log))
                return;

        va_start(args, fmt);
        n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args);
        va_end(args);

        WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
                  "verifier log line truncated - local buffer too short\n");

        n = min(log->len_total - log->len_used - 1, n);
        log->kbuf[n] = '\0';

        if (!copy_to_user(log->ubuf + log->len_used, log->kbuf, n + 1))
                log->len_used += n;
        else
                log->ubuf = NULL;
}

static bool type_is_pkt_pointer(enum bpf_reg_type type)
{
        return type == PTR_TO_PACKET ||
               type == PTR_TO_PACKET_META;
}

/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
        [NOT_INIT]              = "?",
        [SCALAR_VALUE]          = "inv",
        [PTR_TO_CTX]            = "ctx",
        [CONST_PTR_TO_MAP]      = "map_ptr",
        [PTR_TO_MAP_VALUE]      = "map_value",
        [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
        [PTR_TO_STACK]          = "fp",
        [PTR_TO_PACKET]         = "pkt",
        [PTR_TO_PACKET_META]    = "pkt_meta",
        [PTR_TO_PACKET_END]     = "pkt_end",
};

static void print_verifier_state(struct bpf_verifier_env *env,
                                 struct bpf_verifier_state *state)
{
        struct bpf_reg_state *reg;
        enum bpf_reg_type t;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++) {
                reg = &state->regs[i];
                t = reg->type;
                if (t == NOT_INIT)
                        continue;
                verbose(env, " R%d=%s", i, reg_type_str[t]);
                if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
                    tnum_is_const(reg->var_off)) {
                        /* reg->off should be 0 for SCALAR_VALUE */
                        verbose(env, "%lld", reg->var_off.value + reg->off);
                } else {
                        verbose(env, "(id=%d", reg->id);
                        if (t != SCALAR_VALUE)
                                verbose(env, ",off=%d", reg->off);
                        if (type_is_pkt_pointer(t))
                                verbose(env, ",r=%d", reg->range);
                        else if (t == CONST_PTR_TO_MAP ||
                                 t == PTR_TO_MAP_VALUE ||
                                 t == PTR_TO_MAP_VALUE_OR_NULL)
                                verbose(env, ",ks=%d,vs=%d",
                                        reg->map_ptr->key_size,
                                        reg->map_ptr->value_size);
                        if (tnum_is_const(reg->var_off)) {
                                /* Typically an immediate SCALAR_VALUE, but
                                 * could be a pointer whose offset is too big
                                 * for reg->off
                                 */
                                verbose(env, ",imm=%llx", reg->var_off.value);
                        } else {
                                if (reg->smin_value != reg->umin_value &&
                                    reg->smin_value != S64_MIN)
                                        verbose(env, ",smin_value=%lld",
                                                (long long)reg->smin_value);
                                if (reg->smax_value != reg->umax_value &&
                                    reg->smax_value != S64_MAX)
                                        verbose(env, ",smax_value=%lld",
                                                (long long)reg->smax_value);
                                if (reg->umin_value != 0)
                                        verbose(env, ",umin_value=%llu",
                                                (unsigned long long)reg->umin_value);
                                if (reg->umax_value != U64_MAX)
                                        verbose(env, ",umax_value=%llu",
                                                (unsigned long long)reg->umax_value);
                                if (!tnum_is_unknown(reg->var_off)) {
                                        char tn_buf[48];

                                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                                        verbose(env, ",var_off=%s", tn_buf);
                                }
                        }
                        verbose(env, ")");
                }
        }
        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
                if (state->stack[i].slot_type[0] == STACK_SPILL)
                        verbose(env, " fp%d=%s",
                                -MAX_BPF_STACK + i * BPF_REG_SIZE,
                                reg_type_str[state->stack[i].spilled_ptr.type]);
        }
        verbose(env, "\n");
}

static int copy_stack_state(struct bpf_verifier_state *dst,
                            const struct bpf_verifier_state *src)
{
        if (!src->stack)
                return 0;
        if (WARN_ON_ONCE(dst->allocated_stack < src->allocated_stack)) {
                /* internal bug, make state invalid to reject the program */
                memset(dst, 0, sizeof(*dst));
                return -EFAULT;
        }
        memcpy(dst->stack, src->stack,
               sizeof(*src->stack) * (src->allocated_stack / BPF_REG_SIZE));
        return 0;
}

/* do_check() starts with zero-sized stack in struct bpf_verifier_state to
 * make it consume minimal amount of memory. check_stack_write() access from
 * the program calls into realloc_verifier_state() to grow the stack size.
 * Note there is a non-zero 'parent' pointer inside bpf_verifier_state
 * which this function copies over. It points to previous bpf_verifier_state
 * which is never reallocated
 */
static int realloc_verifier_state(struct bpf_verifier_state *state, int size,
                                  bool copy_old)
{
        u32 old_size = state->allocated_stack;
        struct bpf_stack_state *new_stack;
        int slot = size / BPF_REG_SIZE;

        if (size <= old_size || !size) {
                if (copy_old)
                        return 0;
                state->allocated_stack = slot * BPF_REG_SIZE;
                if (!size && old_size) {
                        kfree(state->stack);
                        state->stack = NULL;
                }
                return 0;
        }
        new_stack = kmalloc_array(slot, sizeof(struct bpf_stack_state),
                                  GFP_KERNEL);
        if (!new_stack)
                return -ENOMEM;
        if (copy_old) {
                if (state->stack)
                        memcpy(new_stack, state->stack,
                               sizeof(*new_stack) * (old_size / BPF_REG_SIZE));
                memset(new_stack + old_size / BPF_REG_SIZE, 0,
                       sizeof(*new_stack) * (size - old_size) / BPF_REG_SIZE);
        }
        state->allocated_stack = slot * BPF_REG_SIZE;
        kfree(state->stack);
        state->stack = new_stack;
        return 0;
}

static void free_verifier_state(struct bpf_verifier_state *state,
                                bool free_self)
{
        kfree(state->stack);
        if (free_self)
                kfree(state);
}

/* copy verifier state from src to dst growing dst stack space
 * when necessary to accommodate larger src stack
 */
static int copy_verifier_state(struct bpf_verifier_state *dst,
                               const struct bpf_verifier_state *src)
{
        int err;

        err = realloc_verifier_state(dst, src->allocated_stack, false);
        if (err)
                return err;
        memcpy(dst, src, offsetof(struct bpf_verifier_state, allocated_stack));
        return copy_stack_state(dst, src);
}

static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx,
                     int *insn_idx)
{
        struct bpf_verifier_state *cur = env->cur_state;
        struct bpf_verifier_stack_elem *elem, *head = env->head;
        int err;

        if (env->head == NULL)
                return -ENOENT;

        if (cur) {
                err = copy_verifier_state(cur, &head->st);
                if (err)
                        return err;
        }
        if (insn_idx)
                *insn_idx = head->insn_idx;
        if (prev_insn_idx)
                *prev_insn_idx = head->prev_insn_idx;
        elem = head->next;
        free_verifier_state(&head->st, false);
        kfree(head);
        env->head = elem;
        env->stack_size--;
        return 0;
}

static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
                                             int insn_idx, int prev_insn_idx)
{
        struct bpf_verifier_state *cur = env->cur_state;
        struct bpf_verifier_stack_elem *elem;
        int err;

        elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
        if (!elem)
                goto err;

        elem->insn_idx = insn_idx;
        elem->prev_insn_idx = prev_insn_idx;
        elem->next = env->head;
        env->head = elem;
        env->stack_size++;
        err = copy_verifier_state(&elem->st, cur);
        if (err)
                goto err;
        if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
                verbose(env, "BPF program is too complex\n");
                goto err;
        }
        return &elem->st;
err:
        /* pop all elements and return */
        while (!pop_stack(env, NULL, NULL));
        return NULL;
}

#define CALLER_SAVED_REGS 6
static const int caller_saved[CALLER_SAVED_REGS] = {
        BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
};

static void __mark_reg_not_init(struct bpf_reg_state *reg);

/* Mark the unknown part of a register (variable offset or scalar value) as
 * known to have the value @imm.
 */
static void __mark_reg_known(struct bpf_reg_state *reg, u64 imm)
{
        reg->id = 0;
        reg->var_off = tnum_const(imm);
        reg->smin_value = (s64)imm;
        reg->smax_value = (s64)imm;
        reg->umin_value = imm;
        reg->umax_value = imm;
}

/* Mark the 'variable offset' part of a register as zero.  This should be
 * used only on registers holding a pointer type.
 */
static void __mark_reg_known_zero(struct bpf_reg_state *reg)
{
        __mark_reg_known(reg, 0);
}

static void mark_reg_known_zero(struct bpf_verifier_env *env,
                                struct bpf_reg_state *regs, u32 regno)
{
        if (WARN_ON(regno >= MAX_BPF_REG)) {
                verbose(env, "mark_reg_known_zero(regs, %u)\n", regno);
                /* Something bad happened, let's kill all regs */
                for (regno = 0; regno < MAX_BPF_REG; regno++)
                        __mark_reg_not_init(regs + regno);
                return;
        }
        __mark_reg_known_zero(regs + regno);
}

static bool reg_is_pkt_pointer(const struct bpf_reg_state *reg)
{
        return type_is_pkt_pointer(reg->type);
}

static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg)
{
        return reg_is_pkt_pointer(reg) ||
               reg->type == PTR_TO_PACKET_END;
}

/* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg,
                                    enum bpf_reg_type which)
{
        /* The register can already have a range from prior markings.
         * This is fine as long as it hasn't been advanced from its
         * origin.
         */
        return reg->type == which &&
               reg->id == 0 &&
               reg->off == 0 &&
               tnum_equals_const(reg->var_off, 0);
}

/* Attempts to improve min/max values based on var_off information */
static void __update_reg_bounds(struct bpf_reg_state *reg)
{
        /* min signed is max(sign bit) | min(other bits) */
        reg->smin_value = max_t(s64, reg->smin_value,
                                reg->var_off.value | (reg->var_off.mask & S64_MIN));
        /* max signed is min(sign bit) | max(other bits) */
        reg->smax_value = min_t(s64, reg->smax_value,
                                reg->var_off.value | (reg->var_off.mask & S64_MAX));
        reg->umin_value = max(reg->umin_value, reg->var_off.value);
        reg->umax_value = min(reg->umax_value,
                              reg->var_off.value | reg->var_off.mask);
}

/* Uses signed min/max values to inform unsigned, and vice-versa */
static void __reg_deduce_bounds(struct bpf_reg_state *reg)
{
        /* Learn sign from signed bounds.
         * If we cannot cross the sign boundary, then signed and unsigned bounds
         * are the same, so combine.  This works even in the negative case, e.g.
         * -3 s<= x s<= -1 implies 0xf...fd u<= x u<= 0xf...ff.
         */
        if (reg->smin_value >= 0 || reg->smax_value < 0) {
                reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
                                                          reg->umin_value);
                reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
                                                          reg->umax_value);
                return;
        }
        /* Learn sign from unsigned bounds.  Signed bounds cross the sign
         * boundary, so we must be careful.
         */
        if ((s64)reg->umax_value >= 0) {
                /* Positive.  We can't learn anything from the smin, but smax
                 * is positive, hence safe.
                 */
                reg->smin_value = reg->umin_value;
                reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
                                                          reg->umax_value);
        } else if ((s64)reg->umin_value < 0) {
                /* Negative.  We can't learn anything from the smax, but smin
                 * is negative, hence safe.
                 */
                reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
                                                          reg->umin_value);
                reg->smax_value = reg->umax_value;
        }
}

/* Attempts to improve var_off based on unsigned min/max information */
static void __reg_bound_offset(struct bpf_reg_state *reg)
{
        reg->var_off = tnum_intersect(reg->var_off,
                                      tnum_range(reg->umin_value,
                                                 reg->umax_value));
}

/* Reset the min/max bounds of a register */
static void __mark_reg_unbounded(struct bpf_reg_state *reg)
{
        reg->smin_value = S64_MIN;
        reg->smax_value = S64_MAX;
        reg->umin_value = 0;
        reg->umax_value = U64_MAX;
}

/* Mark a register as having a completely unknown (scalar) value. */
static void __mark_reg_unknown(struct bpf_reg_state *reg)
{
        reg->type = SCALAR_VALUE;
        reg->id = 0;
        reg->off = 0;
        reg->var_off = tnum_unknown;
        __mark_reg_unbounded(reg);
}

static void mark_reg_unknown(struct bpf_verifier_env *env,
                             struct bpf_reg_state *regs, u32 regno)
{
        if (WARN_ON(regno >= MAX_BPF_REG)) {
                verbose(env, "mark_reg_unknown(regs, %u)\n", regno);
                /* Something bad happened, let's kill all regs */
                for (regno = 0; regno < MAX_BPF_REG; regno++)
                        __mark_reg_not_init(regs + regno);
                return;
        }
        __mark_reg_unknown(regs + regno);
}

static void __mark_reg_not_init(struct bpf_reg_state *reg)
{
        __mark_reg_unknown(reg);
        reg->type = NOT_INIT;
}

static void mark_reg_not_init(struct bpf_verifier_env *env,
                              struct bpf_reg_state *regs, u32 regno)
{
        if (WARN_ON(regno >= MAX_BPF_REG)) {
                verbose(env, "mark_reg_not_init(regs, %u)\n", regno);
                /* Something bad happened, let's kill all regs */
                for (regno = 0; regno < MAX_BPF_REG; regno++)
                        __mark_reg_not_init(regs + regno);
                return;
        }
        __mark_reg_not_init(regs + regno);
}

static void init_reg_state(struct bpf_verifier_env *env,
                           struct bpf_reg_state *regs)
{
        int i;

        for (i = 0; i < MAX_BPF_REG; i++) {
                mark_reg_not_init(env, regs, i);
                regs[i].live = REG_LIVE_NONE;
        }

        /* frame pointer */
        regs[BPF_REG_FP].type = PTR_TO_STACK;
        mark_reg_known_zero(env, regs, BPF_REG_FP);

        /* 1st arg to a function */
        regs[BPF_REG_1].type = PTR_TO_CTX;
        mark_reg_known_zero(env, regs, BPF_REG_1);
}

enum reg_arg_type {
        SRC_OP,         /* register is used as source operand */
        DST_OP,         /* register is used as destination operand */
        DST_OP_NO_MARK  /* same as above, check only, don't mark */
};

static void mark_reg_read(const struct bpf_verifier_state *state, u32 regno)
{
        struct bpf_verifier_state *parent = state->parent;

        if (regno == BPF_REG_FP)
                /* We don't need to worry about FP liveness because it's read-only */
                return;

        while (parent) {
                /* if read wasn't screened by an earlier write ... */
                if (state->regs[regno].live & REG_LIVE_WRITTEN)
                        break;
                /* ... then we depend on parent's value */
                parent->regs[regno].live |= REG_LIVE_READ;
                state = parent;
                parent = state->parent;
        }
}

static int check_reg_arg(struct bpf_verifier_env *env, u32 regno,
                         enum reg_arg_type t)
{
        struct bpf_reg_state *regs = env->cur_state->regs;

        if (regno >= MAX_BPF_REG) {
                verbose(env, "R%d is invalid\n", regno);
                return -EINVAL;
        }

        if (t == SRC_OP) {
                /* check whether register used as source operand can be read */
                if (regs[regno].type == NOT_INIT) {
                        verbose(env, "R%d !read_ok\n", regno);
                        return -EACCES;
                }
                mark_reg_read(env->cur_state, regno);
        } else {
                /* check whether register used as dest operand can be written to */
                if (regno == BPF_REG_FP) {
                        verbose(env, "frame pointer is read only\n");
                        return -EACCES;
                }
                regs[regno].live |= REG_LIVE_WRITTEN;
                if (t == DST_OP)
                        mark_reg_unknown(env, regs, regno);
        }
        return 0;
}

static bool is_spillable_regtype(enum bpf_reg_type type)
{
        switch (type) {
        case PTR_TO_MAP_VALUE:
        case PTR_TO_MAP_VALUE_OR_NULL:
        case PTR_TO_STACK:
        case PTR_TO_CTX:
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
        case PTR_TO_PACKET_END:
        case CONST_PTR_TO_MAP:
                return true;
        default:
                return false;
        }
}

/* check_stack_read/write functions track spill/fill of registers,
 * stack boundary and alignment are checked in check_mem_access()
 */
static int check_stack_write(struct bpf_verifier_env *env,
                             struct bpf_verifier_state *state, int off,
                             int size, int value_regno)
{
        int i, slot = -off - 1, spi = slot / BPF_REG_SIZE, err;

        err = realloc_verifier_state(state, round_up(slot + 1, BPF_REG_SIZE),
                                     true);
        if (err)
                return err;
        /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
         * so it's aligned access and [off, off + size) are within stack limits
         */
        if (!env->allow_ptr_leaks &&
            state->stack[spi].slot_type[0] == STACK_SPILL &&
            size != BPF_REG_SIZE) {
                verbose(env, "attempt to corrupt spilled pointer on stack\n");
                return -EACCES;
        }

        if (value_regno >= 0 &&
            is_spillable_regtype(state->regs[value_regno].type)) {

                /* register containing pointer is being spilled into stack */
                if (size != BPF_REG_SIZE) {
                        verbose(env, "invalid size of register spill\n");
                        return -EACCES;
                }

                /* save register state */
                state->stack[spi].spilled_ptr = state->regs[value_regno];
                state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN;

                for (i = 0; i < BPF_REG_SIZE; i++)
                        state->stack[spi].slot_type[i] = STACK_SPILL;
        } else {
                /* regular write of data into stack */
                state->stack[spi].spilled_ptr = (struct bpf_reg_state) {};

                for (i = 0; i < size; i++)
                        state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] =
                                STACK_MISC;
        }
        return 0;
}

static void mark_stack_slot_read(const struct bpf_verifier_state *state, int slot)
{
        struct bpf_verifier_state *parent = state->parent;

        while (parent) {
                /* if read wasn't screened by an earlier write ... */
                if (state->stack[slot].spilled_ptr.live & REG_LIVE_WRITTEN)
                        break;
                /* ... then we depend on parent's value */
                parent->stack[slot].spilled_ptr.live |= REG_LIVE_READ;
                state = parent;
                parent = state->parent;
        }
}

static int check_stack_read(struct bpf_verifier_env *env,
                            struct bpf_verifier_state *state, int off, int size,
                            int value_regno)
{
        int i, slot = -off - 1, spi = slot / BPF_REG_SIZE;
        u8 *stype;

        if (state->allocated_stack <= slot) {
                verbose(env, "invalid read from stack off %d+0 size %d\n",
                        off, size);
                return -EACCES;
        }
        stype = state->stack[spi].slot_type;

        if (stype[0] == STACK_SPILL) {
                if (size != BPF_REG_SIZE) {
                        verbose(env, "invalid size of register spill\n");
                        return -EACCES;
                }
                for (i = 1; i < BPF_REG_SIZE; i++) {
                        if (stype[(slot - i) % BPF_REG_SIZE] != STACK_SPILL) {
                                verbose(env, "corrupted spill memory\n");
                                return -EACCES;
                        }
                }

                if (value_regno >= 0) {
                        /* restore register state from stack */
                        state->regs[value_regno] = state->stack[spi].spilled_ptr;
                        mark_stack_slot_read(state, spi);
                }
                return 0;
        } else {
                for (i = 0; i < size; i++) {
                        if (stype[(slot - i) % BPF_REG_SIZE] != STACK_MISC) {
                                verbose(env, "invalid read from stack off %d+%d size %d\n",
                                        off, i, size);
                                return -EACCES;
                        }
                }
                if (value_regno >= 0)
                        /* have read misc data from the stack */
                        mark_reg_unknown(env, state->regs, value_regno);
                return 0;
        }
}

/* check read/write into map element returned by bpf_map_lookup_elem() */
static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
                              int size, bool zero_size_allowed)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_map *map = regs[regno].map_ptr;

        if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
            off + size > map->value_size) {
                verbose(env, "invalid access to map value, value_size=%d off=%d size=%d\n",
                        map->value_size, off, size);
                return -EACCES;
        }
        return 0;
}

/* check read/write into a map element with possible variable offset */
static int check_map_access(struct bpf_verifier_env *env, u32 regno,
                            int off, int size, bool zero_size_allowed)
{
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_reg_state *reg = &state->regs[regno];
        int err;

        /* We may have adjusted the register to this map value, so we
         * need to try adding each of min_value and max_value to off
         * to make sure our theoretical access will be safe.
         */
        if (env->log.level)
                print_verifier_state(env, state);
        /* The minimum value is only important with signed
         * comparisons where we can't assume the floor of a
         * value is 0.  If we are using signed variables for our
         * index'es we need to make sure that whatever we use
         * will have a set floor within our range.
         */
        if (reg->smin_value < 0) {
                verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
                        regno);
                return -EACCES;
        }
        err = __check_map_access(env, regno, reg->smin_value + off, size,
                                 zero_size_allowed);
        if (err) {
                verbose(env, "R%d min value is outside of the array range\n",
                        regno);
                return err;
        }

        /* If we haven't set a max value then we need to bail since we can't be
         * sure we won't do bad things.
         * If reg->umax_value + off could overflow, treat that as unbounded too.
         */
        if (reg->umax_value >= BPF_MAX_VAR_OFF) {
                verbose(env, "R%d unbounded memory access, make sure to bounds check any array access into a map\n",
                        regno);
                return -EACCES;
        }
        err = __check_map_access(env, regno, reg->umax_value + off, size,
                                 zero_size_allowed);
        if (err)
                verbose(env, "R%d max value is outside of the array range\n",
                        regno);
        return err;
}

#define MAX_PACKET_OFF 0xffff

static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
                                       const struct bpf_call_arg_meta *meta,
                                       enum bpf_access_type t)
{
        switch (env->prog->type) {
        case BPF_PROG_TYPE_LWT_IN:
        case BPF_PROG_TYPE_LWT_OUT:
                /* dst_input() and dst_output() can't write for now */
                if (t == BPF_WRITE)
                        return false;
                /* fallthrough */
        case BPF_PROG_TYPE_SCHED_CLS:
        case BPF_PROG_TYPE_SCHED_ACT:
        case BPF_PROG_TYPE_XDP:
        case BPF_PROG_TYPE_LWT_XMIT:
        case BPF_PROG_TYPE_SK_SKB:
                if (meta)
                        return meta->pkt_access;

                env->seen_direct_write = true;
                return true;
        default:
                return false;
        }
}

static int __check_packet_access(struct bpf_verifier_env *env, u32 regno,
                                 int off, int size, bool zero_size_allowed)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = &regs[regno];

        if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
            (u64)off + size > reg->range) {
                verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
                        off, size, regno, reg->id, reg->off, reg->range);
                return -EACCES;
        }
        return 0;
}

static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
                               int size, bool zero_size_allowed)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = &regs[regno];
        int err;

        /* We may have added a variable offset to the packet pointer; but any
         * reg->range we have comes after that.  We are only checking the fixed
         * offset.
         */

        /* We don't allow negative numbers, because we aren't tracking enough
         * detail to prove they're safe.
         */
        if (reg->smin_value < 0) {
                verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
                        regno);
                return -EACCES;
        }
        err = __check_packet_access(env, regno, off, size, zero_size_allowed);
        if (err) {
                verbose(env, "R%d offset is outside of the packet\n", regno);
                return err;
        }
        return err;
}

/* check access to 'struct bpf_context' fields.  Supports fixed offsets only */
static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
                            enum bpf_access_type t, enum bpf_reg_type *reg_type)
{
        struct bpf_insn_access_aux info = {
                .reg_type = *reg_type,
        };

        if (env->ops->is_valid_access &&
            env->ops->is_valid_access(off, size, t, &info)) {
                /* A non zero info.ctx_field_size indicates that this field is a
                 * candidate for later verifier transformation to load the whole
                 * field and then apply a mask when accessed with a narrower
                 * access than actual ctx access size. A zero info.ctx_field_size
                 * will only allow for whole field access and rejects any other
                 * type of narrower access.
                 */
                *reg_type = info.reg_type;

                env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
                /* remember the offset of last byte accessed in ctx */
                if (env->prog->aux->max_ctx_offset < off + size)
                        env->prog->aux->max_ctx_offset = off + size;
                return 0;
        }

        verbose(env, "invalid bpf_context access off=%d size=%d\n", off, size);
        return -EACCES;
}

static bool __is_pointer_value(bool allow_ptr_leaks,
                               const struct bpf_reg_state *reg)
{
        if (allow_ptr_leaks)
                return false;

        return reg->type != SCALAR_VALUE;
}

static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
{
        return __is_pointer_value(env->allow_ptr_leaks, cur_regs(env) + regno);
}

static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
{
        const struct bpf_reg_state *reg = cur_regs(env) + regno;

        return reg->type == PTR_TO_CTX;
}

static int check_pkt_ptr_alignment(struct bpf_verifier_env *env,
                                   const struct bpf_reg_state *reg,
                                   int off, int size, bool strict)
{
        struct tnum reg_off;
        int ip_align;

        /* Byte size accesses are always allowed. */
        if (!strict || size == 1)
                return 0;

        /* For platforms that do not have a Kconfig enabling
         * CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of
         * NET_IP_ALIGN is universally set to '2'.  And on platforms
         * that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get
         * to this code only in strict mode where we want to emulate
         * the NET_IP_ALIGN==2 checking.  Therefore use an
         * unconditional IP align value of '2'.
         */
        ip_align = 2;

        reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off));
        if (!tnum_is_aligned(reg_off, size)) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env,
                        "misaligned packet access off %d+%s+%d+%d size %d\n",
                        ip_align, tn_buf, reg->off, off, size);
                return -EACCES;
        }

        return 0;
}

static int check_generic_ptr_alignment(struct bpf_verifier_env *env,
                                       const struct bpf_reg_state *reg,
                                       const char *pointer_desc,
                                       int off, int size, bool strict)
{
        struct tnum reg_off;

        /* Byte size accesses are always allowed. */
        if (!strict || size == 1)
                return 0;

        reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));
        if (!tnum_is_aligned(reg_off, size)) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "misaligned %saccess off %s+%d+%d size %d\n",
                        pointer_desc, tn_buf, reg->off, off, size);
                return -EACCES;
        }

        return 0;
}

static int check_ptr_alignment(struct bpf_verifier_env *env,
                               const struct bpf_reg_state *reg,
                               int off, int size)
{
        bool strict = env->strict_alignment;
        const char *pointer_desc = "";

        switch (reg->type) {
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
                /* Special case, because of NET_IP_ALIGN. Given metadata sits
                 * right in front, treat it the very same way.
                 */
                return check_pkt_ptr_alignment(env, reg, off, size, strict);
        case PTR_TO_MAP_VALUE:
                pointer_desc = "value ";
                break;
        case PTR_TO_CTX:
                pointer_desc = "context ";
                break;
        case PTR_TO_STACK:
                pointer_desc = "stack ";
                /* The stack spill tracking logic in check_stack_write()
                 * and check_stack_read() relies on stack accesses being
                 * aligned.
                 */
                strict = true;
                break;
        default:
                break;
        }
        return check_generic_ptr_alignment(env, reg, pointer_desc, off, size,
                                           strict);
}

/* truncate register to smaller size (in bytes)
 * must be called with size < BPF_REG_SIZE
 */
static void coerce_reg_to_size(struct bpf_reg_state *reg, int size)
{
        u64 mask;

        /* clear high bits in bit representation */
        reg->var_off = tnum_cast(reg->var_off, size);

        /* fix arithmetic bounds */
        mask = ((u64)1 << (size * 8)) - 1;
        if ((reg->umin_value & ~mask) == (reg->umax_value & ~mask)) {
                reg->umin_value &= mask;
                reg->umax_value &= mask;
        } else {
                reg->umin_value = 0;
                reg->umax_value = mask;
        }
        reg->smin_value = reg->umin_value;
        reg->smax_value = reg->umax_value;
}

/* check whether memory at (regno + off) is accessible for t = (read | write)
 * if t==write, value_regno is a register which value is stored into memory
 * if t==read, value_regno is a register which will receive the value from memory
 * if t==write && value_regno==-1, some unknown value is stored into memory
 * if t==read && value_regno==-1, don't care what we read from memory
 */
static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno, int off,
                            int bpf_size, enum bpf_access_type t,
                            int value_regno)
{
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = regs + regno;
        int size, err = 0;

        size = bpf_size_to_bytes(bpf_size);
        if (size < 0)
                return size;

        /* alignment checks will add in reg->off themselves */
        err = check_ptr_alignment(env, reg, off, size);
        if (err)
                return err;

        /* for access checks, reg->off is just part of off */
        off += reg->off;

        if (reg->type == PTR_TO_MAP_VALUE) {
                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into map\n", value_regno);
                        return -EACCES;
                }

                err = check_map_access(env, regno, off, size, false);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);

        } else if (reg->type == PTR_TO_CTX) {
                enum bpf_reg_type reg_type = SCALAR_VALUE;

                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into ctx\n", value_regno);
                        return -EACCES;
                }
                /* ctx accesses must be at a fixed offset, so that we can
                 * determine what type of data were returned.
                 */
                if (reg->off) {
                        verbose(env,
                                "dereference of modified ctx ptr R%d off=%d+%d, ctx+const is allowed, ctx+const+const is not\n",
                                regno, reg->off, off - reg->off);
                        return -EACCES;
                }
                if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                        verbose(env,
                                "variable ctx access var_off=%s off=%d size=%d",
                                tn_buf, off, size);
                        return -EACCES;
                }
                err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
                if (!err && t == BPF_READ && value_regno >= 0) {
                        /* ctx access returns either a scalar, or a
                         * PTR_TO_PACKET[_META,_END]. In the latter
                         * case, we know the offset is zero.
                         */
                        if (reg_type == SCALAR_VALUE)
                                mark_reg_unknown(env, regs, value_regno);
                        else
                                mark_reg_known_zero(env, regs,
                                                    value_regno);
                        regs[value_regno].id = 0;
                        regs[value_regno].off = 0;
                        regs[value_regno].range = 0;
                        regs[value_regno].type = reg_type;
                }

        } else if (reg->type == PTR_TO_STACK) {
                /* stack accesses must be at a fixed offset, so that we can
                 * determine what type of data were returned.
                 * See check_stack_read().
                 */
                if (!tnum_is_const(reg->var_off)) {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                        verbose(env, "variable stack access var_off=%s off=%d size=%d",
                                tn_buf, off, size);
                        return -EACCES;
                }
                off += reg->var_off.value;
                if (off >= 0 || off < -MAX_BPF_STACK) {
                        verbose(env, "invalid stack off=%d size=%d\n", off,
                                size);
                        return -EACCES;
                }

                if (env->prog->aux->stack_depth < -off)
                        env->prog->aux->stack_depth = -off;

                if (t == BPF_WRITE)
                        err = check_stack_write(env, state, off, size,
                                                value_regno);
                else
                        err = check_stack_read(env, state, off, size,
                                               value_regno);
        } else if (reg_is_pkt_pointer(reg)) {
                if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) {
                        verbose(env, "cannot write into packet\n");
                        return -EACCES;
                }
                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into packet\n",
                                value_regno);
                        return -EACCES;
                }
                err = check_packet_access(env, regno, off, size, false);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else {
                verbose(env, "R%d invalid mem access '%s'\n", regno,
                        reg_type_str[reg->type]);
                return -EACCES;
        }

        if (!err && size < BPF_REG_SIZE && value_regno >= 0 && t == BPF_READ &&
            regs[value_regno].type == SCALAR_VALUE) {
                /* b/h/w load zero-extends, mark upper bits as known 0 */
                coerce_reg_to_size(&regs[value_regno], size);
        }
        return err;
}

static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
{
        int err;

        if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
            insn->imm != 0) {
                verbose(env, "BPF_XADD uses reserved fields\n");
                return -EINVAL;
        }

        /* check src1 operand */
        err = check_reg_arg(env, insn->src_reg, SRC_OP);
        if (err)
                return err;

        /* check src2 operand */
        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
        if (err)
                return err;

        if (is_pointer_value(env, insn->src_reg)) {
                verbose(env, "R%d leaks addr into mem\n", insn->src_reg);
                return -EACCES;
        }

        if (is_ctx_reg(env, insn->dst_reg)) {
                verbose(env, "BPF_XADD stores into R%d context is not allowed\n",
                        insn->dst_reg);
                return -EACCES;
        }

        /* check whether atomic_add can read the memory */
        err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
                               BPF_SIZE(insn->code), BPF_READ, -1);
        if (err)
                return err;

        /* check whether atomic_add can write into the same memory */
        return check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
                                BPF_SIZE(insn->code), BPF_WRITE, -1);
}

/* Does this register contain a constant zero? */
static bool register_is_null(struct bpf_reg_state reg)
{
        return reg.type == SCALAR_VALUE && tnum_equals_const(reg.var_off, 0);
}

/* when register 'regno' is passed into function that will read 'access_size'
 * bytes from that pointer, make sure that it's within stack boundary
 * and all elements of stack are initialized.
 * Unlike most pointer bounds-checking functions, this one doesn't take an
 * 'off' argument, so it has to add in reg->off itself.
 */
static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
                                int access_size, bool zero_size_allowed,
                                struct bpf_call_arg_meta *meta)
{
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_reg_state *regs = state->regs;
        int off, i, slot, spi;

        if (regs[regno].type != PTR_TO_STACK) {
                /* Allow zero-byte read from NULL, regardless of pointer type */
                if (zero_size_allowed && access_size == 0 &&
                    register_is_null(regs[regno]))
                        return 0;

                verbose(env, "R%d type=%s expected=%s\n", regno,
                        reg_type_str[regs[regno].type],
                        reg_type_str[PTR_TO_STACK]);
                return -EACCES;
        }

        /* Only allow fixed-offset stack reads */
        if (!tnum_is_const(regs[regno].var_off)) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), regs[regno].var_off);
                verbose(env, "invalid variable stack read R%d var_off=%s\n",
                        regno, tn_buf);
                return -EACCES;
        }
        off = regs[regno].off + regs[regno].var_off.value;
        if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
            access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
                verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
                        regno, off, access_size);
                return -EACCES;
        }

        if (env->prog->aux->stack_depth < -off)
                env->prog->aux->stack_depth = -off;

        if (meta && meta->raw_mode) {
                meta->access_size = access_size;
                meta->regno = regno;
                return 0;
        }

        for (i = 0; i < access_size; i++) {
                slot = -(off + i) - 1;
                spi = slot / BPF_REG_SIZE;
                if (state->allocated_stack <= slot ||
                    state->stack[spi].slot_type[slot % BPF_REG_SIZE] !=
                        STACK_MISC) {
                        verbose(env, "invalid indirect read from stack off %d+%d size %d\n",
                                off, i, access_size);
                        return -EACCES;
                }
        }
        return 0;
}

static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
                                   int access_size, bool zero_size_allowed,
                                   struct bpf_call_arg_meta *meta)
{
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];

        switch (reg->type) {
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
                return check_packet_access(env, regno, reg->off, access_size,
                                           zero_size_allowed);
        case PTR_TO_MAP_VALUE:
                return check_map_access(env, regno, reg->off, access_size,
                                        zero_size_allowed);
        default: /* scalar_value|ptr_to_stack or invalid ptr */
                return check_stack_boundary(env, regno, access_size,
                                            zero_size_allowed, meta);
        }
}

static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
                          enum bpf_arg_type arg_type,
                          struct bpf_call_arg_meta *meta)
{
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
        enum bpf_reg_type expected_type, type = reg->type;
        int err = 0;

        if (arg_type == ARG_DONTCARE)
                return 0;

        err = check_reg_arg(env, regno, SRC_OP);
        if (err)
                return err;

        if (arg_type == ARG_ANYTHING) {
                if (is_pointer_value(env, regno)) {
                        verbose(env, "R%d leaks addr into helper function\n",
                                regno);
                        return -EACCES;
                }
                return 0;
        }

        if (type_is_pkt_pointer(type) &&
            !may_access_direct_pkt_data(env, meta, BPF_READ)) {
                verbose(env, "helper access to the packet is not allowed\n");
                return -EACCES;
        }

        if (arg_type == ARG_PTR_TO_MAP_KEY ||
            arg_type == ARG_PTR_TO_MAP_VALUE) {
                expected_type = PTR_TO_STACK;
                if (!type_is_pkt_pointer(type) &&
                    type != expected_type)
                        goto err_type;
        } else if (arg_type == ARG_CONST_SIZE ||
                   arg_type == ARG_CONST_SIZE_OR_ZERO) {
                expected_type = SCALAR_VALUE;
                if (type != expected_type)
                        goto err_type;
        } else if (arg_type == ARG_CONST_MAP_PTR) {
                expected_type = CONST_PTR_TO_MAP;
                if (type != expected_type)
                        goto err_type;
        } else if (arg_type == ARG_PTR_TO_CTX) {
                expected_type = PTR_TO_CTX;
                if (type != expected_type)
                        goto err_type;
        } else if (arg_type == ARG_PTR_TO_MEM ||
                   arg_type == ARG_PTR_TO_MEM_OR_NULL ||
                   arg_type == ARG_PTR_TO_UNINIT_MEM) {
                expected_type = PTR_TO_STACK;
                /* One exception here. In case function allows for NULL to be
                 * passed in as argument, it's a SCALAR_VALUE type. Final test
                 * happens during stack boundary checking.
                 */
                if (register_is_null(*reg) &&
                    arg_type == ARG_PTR_TO_MEM_OR_NULL)
                        /* final test in check_stack_boundary() */;
                else if (!type_is_pkt_pointer(type) &&
                         type != PTR_TO_MAP_VALUE &&
                         type != expected_type)
                        goto err_type;
                meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
        } else {
                verbose(env, "unsupported arg_type %d\n", arg_type);
                return -EFAULT;
        }

        if (arg_type == ARG_CONST_MAP_PTR) {
                /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
                meta->map_ptr = reg->map_ptr;
        } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
                /* bpf_map_xxx(..., map_ptr, ..., key) call:
                 * check that [key, key + map->key_size) are within
                 * stack limits and initialized
                 */
                if (!meta->map_ptr) {
                        /* in function declaration map_ptr must come before
                         * map_key, so that it's verified and known before
                         * we have to check map_key here. Otherwise it means
                         * that kernel subsystem misconfigured verifier
                         */
                        verbose(env, "invalid map_ptr to access map->key\n");
                        return -EACCES;
                }
                if (type_is_pkt_pointer(type))
                        err = check_packet_access(env, regno, reg->off,
                                                  meta->map_ptr->key_size,
                                                  false);
                else
                        err = check_stack_boundary(env, regno,
                                                   meta->map_ptr->key_size,
                                                   false, NULL);
        } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
                /* bpf_map_xxx(..., map_ptr, ..., value) call:
                 * check [value, value + map->value_size) validity
                 */
                if (!meta->map_ptr) {
                        /* kernel subsystem misconfigured verifier */
                        verbose(env, "invalid map_ptr to access map->value\n");
                        return -EACCES;
                }
                if (type_is_pkt_pointer(type))
                        err = check_packet_access(env, regno, reg->off,
                                                  meta->map_ptr->value_size,
                                                  false);
                else
                        err = check_stack_boundary(env, regno,
                                                   meta->map_ptr->value_size,
                                                   false, NULL);
        } else if (arg_type == ARG_CONST_SIZE ||
                   arg_type == ARG_CONST_SIZE_OR_ZERO) {
                bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);

                /* bpf_xxx(..., buf, len) call will access 'len' bytes
                 * from stack pointer 'buf'. Check it
                 * note: regno == len, regno - 1 == buf
                 */
                if (regno == 0) {
                        /* kernel subsystem misconfigured verifier */
                        verbose(env,
                                "ARG_CONST_SIZE cannot be first argument\n");
                        return -EACCES;
                }

                /* The register is SCALAR_VALUE; the access check
                 * happens using its boundaries.
                 */

                if (!tnum_is_const(reg->var_off))
                        /* For unprivileged variable accesses, disable raw
                         * mode so that the program is required to
                         * initialize all the memory that the helper could
                         * just partially fill up.
                         */
                        meta = NULL;

                if (reg->smin_value < 0) {
                        verbose(env, "R%d min value is negative, either use unsigned or 'var &= const'\n",
                                regno);
                        return -EACCES;
                }

                if (reg->umin_value == 0) {
                        err = check_helper_mem_access(env, regno - 1, 0,
                                                      zero_size_allowed,
                                                      meta);
                        if (err)
                                return err;
                }

                if (reg->umax_value >= BPF_MAX_VAR_SIZ) {
                        verbose(env, "R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n",
                                regno);
                        return -EACCES;
                }
                err = check_helper_mem_access(env, regno - 1,
                                              reg->umax_value,
                                              zero_size_allowed, meta);
        }

        return err;
err_type:
        verbose(env, "R%d type=%s expected=%s\n", regno,
                reg_type_str[type], reg_type_str[expected_type]);
        return -EACCES;
}

static int check_map_func_compatibility(struct bpf_verifier_env *env,
                                        struct bpf_map *map, int func_id)
{
        if (!map)
                return 0;

        /* We need a two way check, first is from map perspective ... */
        switch (map->map_type) {
        case BPF_MAP_TYPE_PROG_ARRAY:
                if (func_id != BPF_FUNC_tail_call)
                        goto error;
                break;
        case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
                if (func_id != BPF_FUNC_perf_event_read &&
                    func_id != BPF_FUNC_perf_event_output &&
                    func_id != BPF_FUNC_perf_event_read_value)
                        goto error;
                break;
        case BPF_MAP_TYPE_STACK_TRACE:
                if (func_id != BPF_FUNC_get_stackid)
                        goto error;
                break;
        case BPF_MAP_TYPE_CGROUP_ARRAY:
                if (func_id != BPF_FUNC_skb_under_cgroup &&
                    func_id != BPF_FUNC_current_task_under_cgroup)
                        goto error;
                break;
        /* devmap returns a pointer to a live net_device ifindex that we cannot
         * allow to be modified from bpf side. So do not allow lookup elements
         * for now.
         */
        case BPF_MAP_TYPE_DEVMAP:
                if (func_id != BPF_FUNC_redirect_map)
                        goto error;
                break;
        /* Restrict bpf side of cpumap, open when use-cases appear */
        case BPF_MAP_TYPE_CPUMAP:
                if (func_id != BPF_FUNC_redirect_map)
                        goto error;
                break;
        case BPF_MAP_TYPE_ARRAY_OF_MAPS:
        case BPF_MAP_TYPE_HASH_OF_MAPS:
                if (func_id != BPF_FUNC_map_lookup_elem)
                        goto error;
                break;
        case BPF_MAP_TYPE_SOCKMAP:
                if (func_id != BPF_FUNC_sk_redirect_map &&
                    func_id != BPF_FUNC_sock_map_update &&
                    func_id != BPF_FUNC_map_delete_elem)
                        goto error;
                break;
        default:
                break;
        }

        /* ... and second from the function itself. */
        switch (func_id) {
        case BPF_FUNC_tail_call:
                if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
                        goto error;
                break;
        case BPF_FUNC_perf_event_read:
        case BPF_FUNC_perf_event_output:
        case BPF_FUNC_perf_event_read_value:
                if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
                        goto error;
                break;
        case BPF_FUNC_get_stackid:
                if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
                        goto error;
                break;
        case BPF_FUNC_current_task_under_cgroup:
        case BPF_FUNC_skb_under_cgroup:
                if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
                        goto error;
                break;
        case BPF_FUNC_redirect_map:
                if (map->map_type != BPF_MAP_TYPE_DEVMAP &&
                    map->map_type != BPF_MAP_TYPE_CPUMAP)
                        goto error;
                break;
        case BPF_FUNC_sk_redirect_map:
                if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
                        goto error;
                break;
        case BPF_FUNC_sock_map_update:
                if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
                        goto error;
                break;
        default:
                break;
        }

        return 0;
error:
        verbose(env, "cannot pass map_type %d into func %s#%d\n",
                map->map_type, func_id_name(func_id), func_id);
        return -EINVAL;
}

static int check_raw_mode(const struct bpf_func_proto *fn)
{
        int count = 0;

        if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
                count++;

        return count > 1 ? -EINVAL : 0;
}

/* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
 * are now invalid, so turn them into unknown SCALAR_VALUE.
 */
static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
{
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_reg_state *regs = state->regs, *reg;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++)
                if (reg_is_pkt_pointer_any(&regs[i]))
                        mark_reg_unknown(env, regs, i);

        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
                if (state->stack[i].slot_type[0] != STACK_SPILL)
                        continue;
                reg = &state->stack[i].spilled_ptr;
                if (reg_is_pkt_pointer_any(reg))
                        __mark_reg_unknown(reg);
        }
}

static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
{
        const struct bpf_func_proto *fn = NULL;
        struct bpf_reg_state *regs;
        struct bpf_call_arg_meta meta;
        bool changes_data;
        int i, err;

        /* find function prototype */
        if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
                verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
                        func_id);
                return -EINVAL;
        }

        if (env->ops->get_func_proto)
                fn = env->ops->get_func_proto(func_id);

        if (!fn) {
                verbose(env, "unknown func %s#%d\n", func_id_name(func_id),
                        func_id);
                return -EINVAL;
        }

        /* eBPF programs must be GPL compatible to use GPL-ed functions */
        if (!env->prog->gpl_compatible && fn->gpl_only) {
                verbose(env, "cannot call GPL only function from proprietary program\n");
                return -EINVAL;
        }

        /* With LD_ABS/IND some JITs save/restore skb from r1. */
        changes_data = bpf_helper_changes_pkt_data(fn->func);
        if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
                verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n",
                        func_id_name(func_id), func_id);
                return -EINVAL;
        }

        memset(&meta, 0, sizeof(meta));
        meta.pkt_access = fn->pkt_access;

        /* We only support one arg being in raw mode at the moment, which
         * is sufficient for the helper functions we have right now.
         */
        err = check_raw_mode(fn);
        if (err) {
                verbose(env, "kernel subsystem misconfigured func %s#%d\n",
                        func_id_name(func_id), func_id);
                return err;
        }

        /* check args */
        err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
        if (err)
                return err;
        err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
        if (err)
                return err;
        if (func_id == BPF_FUNC_tail_call) {
                if (meta.map_ptr == NULL) {
                        verbose(env, "verifier bug\n");
                        return -EINVAL;
                }
                env->insn_aux_data[insn_idx].map_ptr = meta.map_ptr;
        }
        err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
        if (err)
                return err;
        err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
        if (err)
                return err;
        err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
        if (err)
                return err;

        /* Mark slots with STACK_MISC in case of raw mode, stack offset
         * is inferred from register state.
         */
        for (i = 0; i < meta.access_size; i++) {
                err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1);
                if (err)
                        return err;
        }

        regs = cur_regs(env);
        /* reset caller saved regs */
        for (i = 0; i < CALLER_SAVED_REGS; i++) {
                mark_reg_not_init(env, regs, caller_saved[i]);
                check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
        }

        /* update return register (already marked as written above) */
        if (fn->ret_type == RET_INTEGER) {
                /* sets type to SCALAR_VALUE */
                mark_reg_unknown(env, regs, BPF_REG_0);
        } else if (fn->ret_type == RET_VOID) {
                regs[BPF_REG_0].type = NOT_INIT;
        } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
                struct bpf_insn_aux_data *insn_aux;

                regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
                /* There is no offset yet applied, variable or fixed */
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].off = 0;
                /* remember map_ptr, so that check_map_access()
                 * can check 'value_size' boundary of memory access
                 * to map element returned from bpf_map_lookup_elem()
                 */
                if (meta.map_ptr == NULL) {
                        verbose(env,
                                "kernel subsystem misconfigured verifier\n");
                        return -EINVAL;
                }
                regs[BPF_REG_0].map_ptr = meta.map_ptr;
                regs[BPF_REG_0].id = ++env->id_gen;
                insn_aux = &env->insn_aux_data[insn_idx];
                if (!insn_aux->map_ptr)
                        insn_aux->map_ptr = meta.map_ptr;
                else if (insn_aux->map_ptr != meta.map_ptr)
                        insn_aux->map_ptr = BPF_MAP_PTR_POISON;
        } else {
                verbose(env, "unknown return type %d of func %s#%d\n",
                        fn->ret_type, func_id_name(func_id), func_id);
                return -EINVAL;
        }

        err = check_map_func_compatibility(env, meta.map_ptr, func_id);
        if (err)
                return err;

        if (changes_data)
                clear_all_pkt_pointers(env);
        return 0;
}

static bool signed_add_overflows(s64 a, s64 b)
{
        /* Do the add in u64, where overflow is well-defined */
        s64 res = (s64)((u64)a + (u64)b);

        if (b < 0)
                return res > a;
        return res < a;
}

static bool signed_sub_overflows(s64 a, s64 b)
{
        /* Do the sub in u64, where overflow is well-defined */
        s64 res = (s64)((u64)a - (u64)b);

        if (b < 0)
                return res < a;
        return res > a;
}

static bool check_reg_sane_offset(struct bpf_verifier_env *env,
                                  const struct bpf_reg_state *reg,
                                  enum bpf_reg_type type)
{
        bool known = tnum_is_const(reg->var_off);
        s64 val = reg->var_off.value;
        s64 smin = reg->smin_value;

        if (known && (val >= BPF_MAX_VAR_OFF || val <= -BPF_MAX_VAR_OFF)) {
                verbose(env, "math between %s pointer and %lld is not allowed\n",
                        reg_type_str[type], val);
                return false;
        }

        if (reg->off >= BPF_MAX_VAR_OFF || reg->off <= -BPF_MAX_VAR_OFF) {
                verbose(env, "%s pointer offset %d is not allowed\n",
                        reg_type_str[type], reg->off);
                return false;
        }

        if (smin == S64_MIN) {
                verbose(env, "math between %s pointer and register with unbounded min value is not allowed\n",
                        reg_type_str[type]);
                return false;
        }

        if (smin >= BPF_MAX_VAR_OFF || smin <= -BPF_MAX_VAR_OFF) {
                verbose(env, "value %lld makes %s pointer be out of bounds\n",
                        smin, reg_type_str[type]);
                return false;
        }

        return true;
}

/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
 * Caller should also handle BPF_MOV case separately.
 * If we return -EACCES, caller may want to try again treating pointer as a
 * scalar.  So we only emit a diagnostic if !env->allow_ptr_leaks.
 */
static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
                                   struct bpf_insn *insn,
                                   const struct bpf_reg_state *ptr_reg,
                                   const struct bpf_reg_state *off_reg)
{
        struct bpf_reg_state *regs = cur_regs(env), *dst_reg;
        bool known = tnum_is_const(off_reg->var_off);
        s64 smin_val = off_reg->smin_value, smax_val = off_reg->smax_value,
            smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
        u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
            umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
        u8 opcode = BPF_OP(insn->code);
        u32 dst = insn->dst_reg;

        dst_reg = &regs[dst];

        if ((known && (smin_val != smax_val || umin_val != umax_val)) ||
            smin_val > smax_val || umin_val > umax_val) {
                /* Taint dst register if offset had invalid bounds derived from
                 * e.g. dead branches.
                 */
                __mark_reg_unknown(dst_reg);
                return 0;
        }

        if (BPF_CLASS(insn->code) != BPF_ALU64) {
                /* 32-bit ALU ops on pointers produce (meaningless) scalars */
                verbose(env,
                        "R%d 32-bit pointer arithmetic prohibited\n",
                        dst);
                return -EACCES;
        }

        if (ptr_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
                verbose(env, "R%d pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL prohibited, null-check it first\n",
                        dst);
                return -EACCES;
        }
        if (ptr_reg->type == CONST_PTR_TO_MAP) {
                verbose(env, "R%d pointer arithmetic on CONST_PTR_TO_MAP prohibited\n",
                        dst);
                return -EACCES;
        }
        if (ptr_reg->type == PTR_TO_PACKET_END) {
                verbose(env, "R%d pointer arithmetic on PTR_TO_PACKET_END prohibited\n",
                        dst);
                return -EACCES;
        }

        /* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
         * The id may be overwritten later if we create a new variable offset.
         */
        dst_reg->type = ptr_reg->type;
        dst_reg->id = ptr_reg->id;

        if (!check_reg_sane_offset(env, off_reg, ptr_reg->type) ||
            !check_reg_sane_offset(env, ptr_reg, ptr_reg->type))
                return -EINVAL;

        switch (opcode) {
        case BPF_ADD:
                /* We can take a fixed offset as long as it doesn't overflow
                 * the s32 'off' field
                 */
                if (known && (ptr_reg->off + smin_val ==
                              (s64)(s32)(ptr_reg->off + smin_val))) {
                        /* pointer += K.  Accumulate it into fixed offset */
                        dst_reg->smin_value = smin_ptr;
                        dst_reg->smax_value = smax_ptr;
                        dst_reg->umin_value = umin_ptr;
                        dst_reg->umax_value = umax_ptr;
                        dst_reg->var_off = ptr_reg->var_off;
                        dst_reg->off = ptr_reg->off + smin_val;
                        dst_reg->range = ptr_reg->range;
                        break;
                }
                /* A new variable offset is created.  Note that off_reg->off
                 * == 0, since it's a scalar.
                 * dst_reg gets the pointer type and since some positive
                 * integer value was added to the pointer, give it a new 'id'
                 * if it's a PTR_TO_PACKET.
                 * this creates a new 'base' pointer, off_reg (variable) gets
                 * added into the variable offset, and we copy the fixed offset
                 * from ptr_reg.
                 */
                if (signed_add_overflows(smin_ptr, smin_val) ||
                    signed_add_overflows(smax_ptr, smax_val)) {
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value = smin_ptr + smin_val;
                        dst_reg->smax_value = smax_ptr + smax_val;
                }
                if (umin_ptr + umin_val < umin_ptr ||
                    umax_ptr + umax_val < umax_ptr) {
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        dst_reg->umin_value = umin_ptr + umin_val;
                        dst_reg->umax_value = umax_ptr + umax_val;
                }
                dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
                dst_reg->off = ptr_reg->off;
                if (reg_is_pkt_pointer(ptr_reg)) {
                        dst_reg->id = ++env->id_gen;
                        /* something was added to pkt_ptr, set range to zero */
                        dst_reg->range = 0;
                }
                break;
        case BPF_SUB:
                if (dst_reg == off_reg) {
                        /* scalar -= pointer.  Creates an unknown scalar */
                        verbose(env, "R%d tried to subtract pointer from scalar\n",
                                dst);
                        return -EACCES;
                }
                /* We don't allow subtraction from FP, because (according to
                 * test_verifier.c test "invalid fp arithmetic", JITs might not
                 * be able to deal with it.
                 */
                if (ptr_reg->type == PTR_TO_STACK) {
                        verbose(env, "R%d subtraction from stack pointer prohibited\n",
                                dst);
                        return -EACCES;
                }
                if (known && (ptr_reg->off - smin_val ==
                              (s64)(s32)(ptr_reg->off - smin_val))) {
                        /* pointer -= K.  Subtract it from fixed offset */
                        dst_reg->smin_value = smin_ptr;
                        dst_reg->smax_value = smax_ptr;
                        dst_reg->umin_value = umin_ptr;
                        dst_reg->umax_value = umax_ptr;
                        dst_reg->var_off = ptr_reg->var_off;
                        dst_reg->id = ptr_reg->id;
                        dst_reg->off = ptr_reg->off - smin_val;
                        dst_reg->range = ptr_reg->range;
                        break;
                }
                /* A new variable offset is created.  If the subtrahend is known
                 * nonnegative, then any reg->range we had before is still good.
                 */
                if (signed_sub_overflows(smin_ptr, smax_val) ||
                    signed_sub_overflows(smax_ptr, smin_val)) {
                        /* Overflow possible, we know nothing */
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value = smin_ptr - smax_val;
                        dst_reg->smax_value = smax_ptr - smin_val;
                }
                if (umin_ptr < umax_val) {
                        /* Overflow possible, we know nothing */
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        /* Cannot overflow (as long as bounds are consistent) */
                        dst_reg->umin_value = umin_ptr - umax_val;
                        dst_reg->umax_value = umax_ptr - umin_val;
                }
                dst_reg->var_off = tnum_sub(ptr_reg->var_off, off_reg->var_off);
                dst_reg->off = ptr_reg->off;
                if (reg_is_pkt_pointer(ptr_reg)) {
                        dst_reg->id = ++env->id_gen;
                        /* something was added to pkt_ptr, set range to zero */
                        if (smin_val < 0)
                                dst_reg->range = 0;
                }
                break;
        case BPF_AND:
        case BPF_OR:
        case BPF_XOR:
                /* bitwise ops on pointers are troublesome, prohibit. */
                verbose(env, "R%d bitwise operator %s on pointer prohibited\n",
                        dst, bpf_alu_string[opcode >> 4]);
                return -EACCES;
        default:
                /* other operators (e.g. MUL,LSH) produce non-pointer results */
                verbose(env, "R%d pointer arithmetic with %s operator prohibited\n",
                        dst, bpf_alu_string[opcode >> 4]);
                return -EACCES;
        }

        if (!check_reg_sane_offset(env, dst_reg, ptr_reg->type))
                return -EINVAL;

        __update_reg_bounds(dst_reg);
        __reg_deduce_bounds(dst_reg);
        __reg_bound_offset(dst_reg);
        return 0;
}

/* WARNING: This function does calculations on 64-bit values, but the actual
 * execution may occur on 32-bit values. Therefore, things like bitshifts
 * need extra checks in the 32-bit case.
 */
static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
                                      struct bpf_insn *insn,
                                      struct bpf_reg_state *dst_reg,
                                      struct bpf_reg_state src_reg)
{
        struct bpf_reg_state *regs = cur_regs(env);
        u8 opcode = BPF_OP(insn->code);
        bool src_known, dst_known;
        s64 smin_val, smax_val;
        u64 umin_val, umax_val;
        u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;

        smin_val = src_reg.smin_value;
        smax_val = src_reg.smax_value;
        umin_val = src_reg.umin_value;
        umax_val = src_reg.umax_value;
        src_known = tnum_is_const(src_reg.var_off);
        dst_known = tnum_is_const(dst_reg->var_off);

        if ((src_known && (smin_val != smax_val || umin_val != umax_val)) ||
            smin_val > smax_val || umin_val > umax_val) {
                /* Taint dst register if offset had invalid bounds derived from
                 * e.g. dead branches.
                 */
                __mark_reg_unknown(dst_reg);
                return 0;
        }

        if (!src_known &&
            opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) {
                __mark_reg_unknown(dst_reg);
                return 0;
        }

        switch (opcode) {
        case BPF_ADD:
                if (signed_add_overflows(dst_reg->smin_value, smin_val) ||
                    signed_add_overflows(dst_reg->smax_value, smax_val)) {
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value += smin_val;
                        dst_reg->smax_value += smax_val;
                }
                if (dst_reg->umin_value + umin_val < umin_val ||
                    dst_reg->umax_value + umax_val < umax_val) {
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        dst_reg->umin_value += umin_val;
                        dst_reg->umax_value += umax_val;
                }
                dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
                break;
        case BPF_SUB:
                if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
                    signed_sub_overflows(dst_reg->smax_value, smin_val)) {
                        /* Overflow possible, we know nothing */
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value -= smax_val;
                        dst_reg->smax_value -= smin_val;
                }
                if (dst_reg->umin_value < umax_val) {
                        /* Overflow possible, we know nothing */
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        /* Cannot overflow (as long as bounds are consistent) */
                        dst_reg->umin_value -= umax_val;
                        dst_reg->umax_value -= umin_val;
                }
                dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);
                break;
        case BPF_MUL:
                dst_reg->var_off = tnum_mul(dst_reg->var_off, src_reg.var_off);
                if (smin_val < 0 || dst_reg->smin_value < 0) {
                        /* Ain't nobody got time to multiply that sign */
                        __mark_reg_unbounded(dst_reg);
                        __update_reg_bounds(dst_reg);
                        break;
                }
                /* Both values are positive, so we can work with unsigned and
                 * copy the result to signed (unless it exceeds S64_MAX).
                 */
                if (umax_val > U32_MAX || dst_reg->umax_value > U32_MAX) {
                        /* Potential overflow, we know nothing */
                        __mark_reg_unbounded(dst_reg);
                        /* (except what we can learn from the var_off) */
                        __update_reg_bounds(dst_reg);
                        break;
                }
                dst_reg->umin_value *= umin_val;
                dst_reg->umax_value *= umax_val;
                if (dst_reg->umax_value > S64_MAX) {
                        /* Overflow possible, we know nothing */
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value = dst_reg->umin_value;
                        dst_reg->smax_value = dst_reg->umax_value;
                }
                break;
        case BPF_AND:
                if (src_known && dst_known) {
                        __mark_reg_known(dst_reg, dst_reg->var_off.value &
                                                  src_reg.var_off.value);
                        break;
                }
                /* We get our minimum from the var_off, since that's inherently
                 * bitwise.  Our maximum is the minimum of the operands' maxima.
                 */
                dst_reg->var_off = tnum_and(dst_reg->var_off, src_reg.var_off);
                dst_reg->umin_value = dst_reg->var_off.value;
                dst_reg->umax_value = min(dst_reg->umax_value, umax_val);
                if (dst_reg->smin_value < 0 || smin_val < 0) {
                        /* Lose signed bounds when ANDing negative numbers,
                         * ain't nobody got time for that.
                         */
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        /* ANDing two positives gives a positive, so safe to
                         * cast result into s64.
                         */
                        dst_reg->smin_value = dst_reg->umin_value;
                        dst_reg->smax_value = dst_reg->umax_value;
                }
                /* We may learn something more from the var_off */
                __update_reg_bounds(dst_reg);
                break;
        case BPF_OR:
                if (src_known && dst_known) {
                        __mark_reg_known(dst_reg, dst_reg->var_off.value |
                                                  src_reg.var_off.value);
                        break;
                }
                /* We get our maximum from the var_off, and our minimum is the
                 * maximum of the operands' minima
                 */
                dst_reg->var_off = tnum_or(dst_reg->var_off, src_reg.var_off);
                dst_reg->umin_value = max(dst_reg->umin_value, umin_val);
                dst_reg->umax_value = dst_reg->var_off.value |
                                      dst_reg->var_off.mask;
                if (dst_reg->smin_value < 0 || smin_val < 0) {
                        /* Lose signed bounds when ORing negative numbers,
                         * ain't nobody got time for that.
                         */
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        /* ORing two positives gives a positive, so safe to
                         * cast result into s64.
                         */
                        dst_reg->smin_value = dst_reg->umin_value;
                        dst_reg->smax_value = dst_reg->umax_value;
                }
                /* We may learn something more from the var_off */
                __update_reg_bounds(dst_reg);
                break;
        case BPF_LSH:
                if (umax_val >= insn_bitness) {
                        /* Shifts greater than 31 or 63 are undefined.
                         * This includes shifts by a negative number.
                         */
                        mark_reg_unknown(env, regs, insn->dst_reg);
                        break;
                }
                /* We lose all sign bit information (except what we can pick
                 * up from var_off)
                 */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
                /* If we might shift our top bit out, then we know nothing */
                if (dst_reg->umax_value > 1ULL << (63 - umax_val)) {
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        dst_reg->umin_value <<= umin_val;
                        dst_reg->umax_value <<= umax_val;
                }
                if (src_known)
                        dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
                else
                        dst_reg->var_off = tnum_lshift(tnum_unknown, umin_val);
                /* We may learn something more from the var_off */
                __update_reg_bounds(dst_reg);
                break;
        case BPF_RSH:
                if (umax_val >= insn_bitness) {
                        /* Shifts greater than 31 or 63 are undefined.
                         * This includes shifts by a negative number.
                         */
                        mark_reg_unknown(env, regs, insn->dst_reg);
                        break;
                }
                /* BPF_RSH is an unsigned shift.  If the value in dst_reg might
                 * be negative, then either:
                 * 1) src_reg might be zero, so the sign bit of the result is
                 *    unknown, so we lose our signed bounds
                 * 2) it's known negative, thus the unsigned bounds capture the
                 *    signed bounds
                 * 3) the signed bounds cross zero, so they tell us nothing
                 *    about the result
                 * If the value in dst_reg is known nonnegative, then again the
                 * unsigned bounts capture the signed bounds.
                 * Thus, in all cases it suffices to blow away our signed bounds
                 * and rely on inferring new ones from the unsigned bounds and
                 * var_off of the result.
                 */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
                if (src_known)
                        dst_reg->var_off = tnum_rshift(dst_reg->var_off,
                                                       umin_val);
                else
                        dst_reg->var_off = tnum_rshift(tnum_unknown, umin_val);
                dst_reg->umin_value >>= umax_val;
                dst_reg->umax_value >>= umin_val;
                /* We may learn something more from the var_off */
                __update_reg_bounds(dst_reg);
                break;
        default:
                mark_reg_unknown(env, regs, insn->dst_reg);
                break;
        }

        if (BPF_CLASS(insn->code) != BPF_ALU64) {
                /* 32-bit ALU ops are (32,32)->32 */
                coerce_reg_to_size(dst_reg, 4);
                coerce_reg_to_size(&src_reg, 4);
        }

        __reg_deduce_bounds(dst_reg);
        __reg_bound_offset(dst_reg);
        return 0;
}

/* Handles ALU ops other than BPF_END, BPF_NEG and BPF_MOV: computes new min/max
 * and var_off.
 */
static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
                                   struct bpf_insn *insn)
{
        struct bpf_reg_state *regs = cur_regs(env), *dst_reg, *src_reg;
        struct bpf_reg_state *ptr_reg = NULL, off_reg = {0};
        u8 opcode = BPF_OP(insn->code);

        dst_reg = &regs[insn->dst_reg];
        src_reg = NULL;
        if (dst_reg->type != SCALAR_VALUE)
                ptr_reg = dst_reg;
        if (BPF_SRC(insn->code) == BPF_X) {
                src_reg = &regs[insn->src_reg];
                if (src_reg->type != SCALAR_VALUE) {
                        if (dst_reg->type != SCALAR_VALUE) {
                                /* Combining two pointers by any ALU op yields
                                 * an arbitrary scalar. Disallow all math except
                                 * pointer subtraction
                                 */
                                if (opcode == BPF_SUB){
                                        mark_reg_unknown(env, regs, insn->dst_reg);
                                        return 0;
                                }
                                verbose(env, "R%d pointer %s pointer prohibited\n",
                                        insn->dst_reg,
                                        bpf_alu_string[opcode >> 4]);
                                return -EACCES;
                        } else {
                                /* scalar += pointer
                                 * This is legal, but we have to reverse our
                                 * src/dest handling in computing the range
                                 */
                                return adjust_ptr_min_max_vals(env, insn,
                                                               src_reg, dst_reg);
                        }
                } else if (ptr_reg) {
                        /* pointer += scalar */
                        return adjust_ptr_min_max_vals(env, insn,
                                                       dst_reg, src_reg);
                }
        } else {
                /* Pretend the src is a reg with a known value, since we only
                 * need to be able to read from this state.
                 */
                off_reg.type = SCALAR_VALUE;
                __mark_reg_known(&off_reg, insn->imm);
                src_reg = &off_reg;
                if (ptr_reg) /* pointer += K */
                        return adjust_ptr_min_max_vals(env, insn,
                                                       ptr_reg, src_reg);
        }

        /* Got here implies adding two SCALAR_VALUEs */
        if (WARN_ON_ONCE(ptr_reg)) {
                print_verifier_state(env, env->cur_state);
                verbose(env, "verifier internal error: unexpected ptr_reg\n");
                return -EINVAL;
        }
        if (WARN_ON(!src_reg)) {
                print_verifier_state(env, env->cur_state);
                verbose(env, "verifier internal error: no src_reg\n");
                return -EINVAL;
        }
        return adjust_scalar_min_max_vals(env, insn, dst_reg, *src_reg);
}

/* check validity of 32-bit and 64-bit arithmetic operations */
static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        struct bpf_reg_state *regs = cur_regs(env);
        u8 opcode = BPF_OP(insn->code);
        int err;

        if (opcode == BPF_END || opcode == BPF_NEG) {
                if (opcode == BPF_NEG) {
                        if (BPF_SRC(insn->code) != 0 ||
                            insn->src_reg != BPF_REG_0 ||
                            insn->off != 0 || insn->imm != 0) {
                                verbose(env, "BPF_NEG uses reserved fields\n");
                                return -EINVAL;
                        }
                } else {
                        if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
                            (insn->imm != 16 && insn->imm != 32 && insn->imm != 64) ||
                            BPF_CLASS(insn->code) == BPF_ALU64) {
                                verbose(env, "BPF_END uses reserved fields\n");
                                return -EINVAL;
                        }
                }

                /* check src operand */
                err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                if (err)
                        return err;

                if (is_pointer_value(env, insn->dst_reg)) {
                        verbose(env, "R%d pointer arithmetic prohibited\n",
                                insn->dst_reg);
                        return -EACCES;
                }

                /* check dest operand */
                err = check_reg_arg(env, insn->dst_reg, DST_OP);
                if (err)
                        return err;

        } else if (opcode == BPF_MOV) {

                if (BPF_SRC(insn->code) == BPF_X) {
                        if (insn->imm != 0 || insn->off != 0) {
                                verbose(env, "BPF_MOV uses reserved fields\n");
                                return -EINVAL;
                        }

                        /* check src operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;
                } else {
                        if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
                                verbose(env, "BPF_MOV uses reserved fields\n");
                                return -EINVAL;
                        }
                }

                /* check dest operand */
                err = check_reg_arg(env, insn->dst_reg, DST_OP);
                if (err)
                        return err;

                if (BPF_SRC(insn->code) == BPF_X) {
                        if (BPF_CLASS(insn->code) == BPF_ALU64) {
                                /* case: R1 = R2
                                 * copy register state to dest reg
                                 */
                                regs[insn->dst_reg] = regs[insn->src_reg];
                                regs[insn->dst_reg].live |= REG_LIVE_WRITTEN;
                        } else {
                                /* R1 = (u32) R2 */
                                if (is_pointer_value(env, insn->src_reg)) {
                                        verbose(env,
                                                "R%d partial copy of pointer\n",
                                                insn->src_reg);
                                        return -EACCES;
                                }
                                mark_reg_unknown(env, regs, insn->dst_reg);
                                coerce_reg_to_size(&regs[insn->dst_reg], 4);
                        }
                } else {
                        /* case: R = imm
                         * remember the value we stored into this reg
                         */
                        regs[insn->dst_reg].type = SCALAR_VALUE;
                        if (BPF_CLASS(insn->code) == BPF_ALU64) {
                                __mark_reg_known(regs + insn->dst_reg,
                                                 insn->imm);
                        } else {
                                __mark_reg_known(regs + insn->dst_reg,
                                                 (u32)insn->imm);
                        }
                }

        } else if (opcode > BPF_END) {
                verbose(env, "invalid BPF_ALU opcode %x\n", opcode);
                return -EINVAL;

        } else {        /* all other ALU ops: and, sub, xor, add, ... */

                if (BPF_SRC(insn->code) == BPF_X) {
                        if (insn->imm != 0 || insn->off != 0) {
                                verbose(env, "BPF_ALU uses reserved fields\n");
                                return -EINVAL;
                        }
                        /* check src1 operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;
                } else {
                        if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
                                verbose(env, "BPF_ALU uses reserved fields\n");
                                return -EINVAL;
                        }
                }

                /* check src2 operand */
                err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                if (err)
                        return err;

                if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
                    BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
                        verbose(env, "div by zero\n");
                        return -EINVAL;
                }

                if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) {
                        verbose(env, "BPF_ARSH not supported for 32 bit ALU\n");
                        return -EINVAL;
                }

                if ((opcode == BPF_LSH || opcode == BPF_RSH ||
                     opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
                        int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;

                        if (insn->imm < 0 || insn->imm >= size) {
                                verbose(env, "invalid shift %d\n", insn->imm);
                                return -EINVAL;
                        }
                }

                /* check dest operand */
                err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
                if (err)
                        return err;

                return adjust_reg_min_max_vals(env, insn);
        }

        return 0;
}

static void find_good_pkt_pointers(struct bpf_verifier_state *state,
                                   struct bpf_reg_state *dst_reg,
                                   enum bpf_reg_type type,
                                   bool range_right_open)
{
        struct bpf_reg_state *regs = state->regs, *reg;
        u16 new_range;
        int i;

        if (dst_reg->off < 0 ||
            (dst_reg->off == 0 && range_right_open))
                /* This doesn't give us any range */
                return;

        if (dst_reg->umax_value > MAX_PACKET_OFF ||
            dst_reg->umax_value + dst_reg->off > MAX_PACKET_OFF)
                /* Risk of overflow.  For instance, ptr + (1<<63) may be less
                 * than pkt_end, but that's because it's also less than pkt.
                 */
                return;

        new_range = dst_reg->off;
        if (range_right_open)
                new_range--;

        /* Examples for register markings:
         *
         * pkt_data in dst register:
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (r2 > pkt_end) goto <handle exception>
         *   <access okay>
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (r2 < pkt_end) goto <access okay>
         *   <handle exception>
         *
         *   Where:
         *     r2 == dst_reg, pkt_end == src_reg
         *     r2=pkt(id=n,off=8,r=0)
         *     r3=pkt(id=n,off=0,r=0)
         *
         * pkt_data in src register:
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (pkt_end >= r2) goto <access okay>
         *   <handle exception>
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (pkt_end <= r2) goto <handle exception>
         *   <access okay>
         *
         *   Where:
         *     pkt_end == dst_reg, r2 == src_reg
         *     r2=pkt(id=n,off=8,r=0)
         *     r3=pkt(id=n,off=0,r=0)
         *
         * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
         * or r3=pkt(id=n,off=0,r=8-1), so that range of bytes [r3, r3 + 8)
         * and [r3, r3 + 8-1) respectively is safe to access depending on
         * the check.
         */

        /* If our ids match, then we must have the same max_value.  And we
         * don't care about the other reg's fixed offset, since if it's too big
         * the range won't allow anything.
         * dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16.
         */
        for (i = 0; i < MAX_BPF_REG; i++)
                if (regs[i].type == type && regs[i].id == dst_reg->id)
                        /* keep the maximum range already checked */
                        regs[i].range = max(regs[i].range, new_range);

        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
                if (state->stack[i].slot_type[0] != STACK_SPILL)
                        continue;
                reg = &state->stack[i].spilled_ptr;
                if (reg->type == type && reg->id == dst_reg->id)
                        reg->range = max(reg->range, new_range);
        }
}

/* Adjusts the register min/max values in the case that the dst_reg is the
 * variable register that we are working on, and src_reg is a constant or we're
 * simply doing a BPF_K check.
 * In JEQ/JNE cases we also adjust the var_off values.
 */
static void reg_set_min_max(struct bpf_reg_state *true_reg,
                            struct bpf_reg_state *false_reg, u64 val,
                            u8 opcode)
{
        /* If the dst_reg is a pointer, we can't learn anything about its
         * variable offset from the compare (unless src_reg were a pointer into
         * the same object, but we don't bother with that.
         * Since false_reg and true_reg have the same type by construction, we
         * only need to check one of them for pointerness.
         */
        if (__is_pointer_value(false, false_reg))
                return;

        switch (opcode) {
        case BPF_JEQ:
                /* If this is false then we know nothing Jon Snow, but if it is
                 * true then we know for sure.
                 */
                __mark_reg_known(true_reg, val);
                break;
        case BPF_JNE:
                /* If this is true we know nothing Jon Snow, but if it is false
                 * we know the value for sure;
                 */
                __mark_reg_known(false_reg, val);
                break;
        case BPF_JGT:
                false_reg->umax_value = min(false_reg->umax_value, val);
                true_reg->umin_value = max(true_reg->umin_value, val + 1);
                break;
        case BPF_JSGT:
                false_reg->smax_value = min_t(s64, false_reg->smax_value, val);
                true_reg->smin_value = max_t(s64, true_reg->smin_value, val + 1);
                break;
        case BPF_JLT:
                false_reg->umin_value = max(false_reg->umin_value, val);
                true_reg->umax_value = min(true_reg->umax_value, val - 1);
                break;
        case BPF_JSLT:
                false_reg->smin_value = max_t(s64, false_reg->smin_value, val);
                true_reg->smax_value = min_t(s64, true_reg->smax_value, val - 1);
                break;
        case BPF_JGE:
                false_reg->umax_value = min(false_reg->umax_value, val - 1);
                true_reg->umin_value = max(true_reg->umin_value, val);
                break;
        case BPF_JSGE:
                false_reg->smax_value = min_t(s64, false_reg->smax_value, val - 1);
                true_reg->smin_value = max_t(s64, true_reg->smin_value, val);
                break;
        case BPF_JLE:
                false_reg->umin_value = max(false_reg->umin_value, val + 1);
                true_reg->umax_value = min(true_reg->umax_value, val);
                break;
        case BPF_JSLE:
                false_reg->smin_value = max_t(s64, false_reg->smin_value, val + 1);
                true_reg->smax_value = min_t(s64, true_reg->smax_value, val);
                break;
        default:
                break;
        }

        __reg_deduce_bounds(false_reg);
        __reg_deduce_bounds(true_reg);
        /* We might have learned some bits from the bounds. */
        __reg_bound_offset(false_reg);
        __reg_bound_offset(true_reg);
        /* Intersecting with the old var_off might have improved our bounds
         * slightly.  e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
         * then new var_off is (0; 0x7f...fc) which improves our umax.
         */
        __update_reg_bounds(false_reg);
        __update_reg_bounds(true_reg);
}

/* Same as above, but for the case that dst_reg holds a constant and src_reg is
 * the variable reg.
 */
static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
                                struct bpf_reg_state *false_reg, u64 val,
                                u8 opcode)
{
        if (__is_pointer_value(false, false_reg))
                return;

        switch (opcode) {
        case BPF_JEQ:
                /* If this is false then we know nothing Jon Snow, but if it is
                 * true then we know for sure.
                 */
                __mark_reg_known(true_reg, val);
                break;
        case BPF_JNE:
                /* If this is true we know nothing Jon Snow, but if it is false
                 * we know the value for sure;
                 */
                __mark_reg_known(false_reg, val);
                break;
        case BPF_JGT:
                true_reg->umax_value = min(true_reg->umax_value, val - 1);
                false_reg->umin_value = max(false_reg->umin_value, val);
                break;
        case BPF_JSGT:
                true_reg->smax_value = min_t(s64, true_reg->smax_value, val - 1);
                false_reg->smin_value = max_t(s64, false_reg->smin_value, val);
                break;
        case BPF_JLT:
                true_reg->umin_value = max(true_reg->umin_value, val + 1);
                false_reg->umax_value = min(false_reg->umax_value, val);
                break;
        case BPF_JSLT:
                true_reg->smin_value = max_t(s64, true_reg->smin_value, val + 1);
                false_reg->smax_value = min_t(s64, false_reg->smax_value, val);
                break;
        case BPF_JGE:
                true_reg->umax_value = min(true_reg->umax_value, val);
                false_reg->umin_value = max(false_reg->umin_value, val + 1);
                break;
        case BPF_JSGE:
                true_reg->smax_value = min_t(s64, true_reg->smax_value, val);
                false_reg->smin_value = max_t(s64, false_reg->smin_value, val + 1);
                break;
        case BPF_JLE:
                true_reg->umin_value = max(true_reg->umin_value, val);
                false_reg->umax_value = min(false_reg->umax_value, val - 1);
                break;
        case BPF_JSLE:
                true_reg->smin_value = max_t(s64, true_reg->smin_value, val);
                false_reg->smax_value = min_t(s64, false_reg->smax_value, val - 1);
                break;
        default:
                break;
        }

        __reg_deduce_bounds(false_reg);
        __reg_deduce_bounds(true_reg);
        /* We might have learned some bits from the bounds. */
        __reg_bound_offset(false_reg);
        __reg_bound_offset(true_reg);
        /* Intersecting with the old var_off might have improved our bounds
         * slightly.  e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
         * then new var_off is (0; 0x7f...fc) which improves our umax.
         */
        __update_reg_bounds(false_reg);
        __update_reg_bounds(true_reg);
}

/* Regs are known to be equal, so intersect their min/max/var_off */
static void __reg_combine_min_max(struct bpf_reg_state *src_reg,
                                  struct bpf_reg_state *dst_reg)
{
        src_reg->umin_value = dst_reg->umin_value = max(src_reg->umin_value,
                                                        dst_reg->umin_value);
        src_reg->umax_value = dst_reg->umax_value = min(src_reg->umax_value,
                                                        dst_reg->umax_value);
        src_reg->smin_value = dst_reg->smin_value = max(src_reg->smin_value,
                                                        dst_reg->smin_value);
        src_reg->smax_value = dst_reg->smax_value = min(src_reg->smax_value,
                                                        dst_reg->smax_value);
        src_reg->var_off = dst_reg->var_off = tnum_intersect(src_reg->var_off,
                                                             dst_reg->var_off);
        /* We might have learned new bounds from the var_off. */
        __update_reg_bounds(src_reg);
        __update_reg_bounds(dst_reg);
        /* We might have learned something about the sign bit. */
        __reg_deduce_bounds(src_reg);
        __reg_deduce_bounds(dst_reg);
        /* We might have learned some bits from the bounds. */
        __reg_bound_offset(src_reg);
        __reg_bound_offset(dst_reg);
        /* Intersecting with the old var_off might have improved our bounds
         * slightly.  e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
         * then new var_off is (0; 0x7f...fc) which improves our umax.
         */
        __update_reg_bounds(src_reg);
        __update_reg_bounds(dst_reg);
}

static void reg_combine_min_max(struct bpf_reg_state *true_src,
                                struct bpf_reg_state *true_dst,
                                struct bpf_reg_state *false_src,
                                struct bpf_reg_state *false_dst,
                                u8 opcode)
{
        switch (opcode) {
        case BPF_JEQ:
                __reg_combine_min_max(true_src, true_dst);
                break;
        case BPF_JNE:
                __reg_combine_min_max(false_src, false_dst);
                break;
        }
}

static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
                         bool is_null)
{
        struct bpf_reg_state *reg = &regs[regno];

        if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) {
                /* Old offset (both fixed and variable parts) should
                 * have been known-zero, because we don't allow pointer
                 * arithmetic on pointers that might be NULL.
                 */
                if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
                                 !tnum_equals_const(reg->var_off, 0) ||
                                 reg->off)) {
                        __mark_reg_known_zero(reg);
                        reg->off = 0;
                }
                if (is_null) {
                        reg->type = SCALAR_VALUE;
                } else if (reg->map_ptr->inner_map_meta) {
                        reg->type = CONST_PTR_TO_MAP;
                        reg->map_ptr = reg->map_ptr->inner_map_meta;
                } else {
                        reg->type = PTR_TO_MAP_VALUE;
                }
                /* We don't need id from this point onwards anymore, thus we
                 * should better reset it, so that state pruning has chances
                 * to take effect.
                 */
                reg->id = 0;
        }
}

/* The logic is similar to find_good_pkt_pointers(), both could eventually
 * be folded together at some point.
 */
static void mark_map_regs(struct bpf_verifier_state *state, u32 regno,
                          bool is_null)
{
        struct bpf_reg_state *regs = state->regs;
        u32 id = regs[regno].id;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++)
                mark_map_reg(regs, i, id, is_null);

        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
                if (state->stack[i].slot_type[0] != STACK_SPILL)
                        continue;
                mark_map_reg(&state->stack[i].spilled_ptr, 0, id, is_null);
        }
}

static bool try_match_pkt_pointers(const struct bpf_insn *insn,
                                   struct bpf_reg_state *dst_reg,
                                   struct bpf_reg_state *src_reg,
                                   struct bpf_verifier_state *this_branch,
                                   struct bpf_verifier_state *other_branch)
{
        if (BPF_SRC(insn->code) != BPF_X)
                return false;

        switch (BPF_OP(insn->code)) {
        case BPF_JGT:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' > pkt_end, pkt_meta' > pkt_data */
                        find_good_pkt_pointers(this_branch, dst_reg,
                                               dst_reg->type, false);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end > pkt_data', pkt_data > pkt_meta' */
                        find_good_pkt_pointers(other_branch, src_reg,
                                               src_reg->type, true);
                } else {
                        return false;
                }
                break;
        case BPF_JLT:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' < pkt_end, pkt_meta' < pkt_data */
                        find_good_pkt_pointers(other_branch, dst_reg,
                                               dst_reg->type, true);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end < pkt_data', pkt_data > pkt_meta' */
                        find_good_pkt_pointers(this_branch, src_reg,
                                               src_reg->type, false);
                } else {
                        return false;
                }
                break;
        case BPF_JGE:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' >= pkt_end, pkt_meta' >= pkt_data */
                        find_good_pkt_pointers(this_branch, dst_reg,
                                               dst_reg->type, true);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end >= pkt_data', pkt_data >= pkt_meta' */
                        find_good_pkt_pointers(other_branch, src_reg,
                                               src_reg->type, false);
                } else {
                        return false;
                }
                break;
        case BPF_JLE:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' <= pkt_end, pkt_meta' <= pkt_data */
                        find_good_pkt_pointers(other_branch, dst_reg,
                                               dst_reg->type, false);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end <= pkt_data', pkt_data <= pkt_meta' */
                        find_good_pkt_pointers(this_branch, src_reg,
                                               src_reg->type, true);
                } else {
                        return false;
                }
                break;
        default:
                return false;
        }

        return true;
}

static int check_cond_jmp_op(struct bpf_verifier_env *env,
                             struct bpf_insn *insn, int *insn_idx)
{
        struct bpf_verifier_state *other_branch, *this_branch = env->cur_state;
        struct bpf_reg_state *regs = this_branch->regs, *dst_reg;
        u8 opcode = BPF_OP(insn->code);
        int err;

        if (opcode > BPF_JSLE) {
                verbose(env, "invalid BPF_JMP opcode %x\n", opcode);
                return -EINVAL;
        }

        if (BPF_SRC(insn->code) == BPF_X) {
                if (insn->imm != 0) {
                        verbose(env, "BPF_JMP uses reserved fields\n");
                        return -EINVAL;
                }

                /* check src1 operand */
                err = check_reg_arg(env, insn->src_reg, SRC_OP);
                if (err)
                        return err;

                if (is_pointer_value(env, insn->src_reg)) {
                        verbose(env, "R%d pointer comparison prohibited\n",
                                insn->src_reg);
                        return -EACCES;
                }
        } else {
                if (insn->src_reg != BPF_REG_0) {
                        verbose(env, "BPF_JMP uses reserved fields\n");
                        return -EINVAL;
                }
        }

        /* check src2 operand */
        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
        if (err)
                return err;

        dst_reg = &regs[insn->dst_reg];

        /* detect if R == 0 where R was initialized to zero earlier */
        if (BPF_SRC(insn->code) == BPF_K &&
            (opcode == BPF_JEQ || opcode == BPF_JNE) &&
            dst_reg->type == SCALAR_VALUE &&
            tnum_equals_const(dst_reg->var_off, insn->imm)) {
                if (opcode == BPF_JEQ) {
                        /* if (imm == imm) goto pc+off;
                         * only follow the goto, ignore fall-through
                         */
                        *insn_idx += insn->off;
                        return 0;
                } else {
                        /* if (imm != imm) goto pc+off;
                         * only follow fall-through branch, since
                         * that's where the program will go
                         */
                        return 0;
                }
        }

        other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
        if (!other_branch)
                return -EFAULT;

        /* detect if we are comparing against a constant value so we can adjust
         * our min/max values for our dst register.
         * this is only legit if both are scalars (or pointers to the same
         * object, I suppose, but we don't support that right now), because
         * otherwise the different base pointers mean the offsets aren't
         * comparable.
         */
        if (BPF_SRC(insn->code) == BPF_X) {
                if (dst_reg->type == SCALAR_VALUE &&
                    regs[insn->src_reg].type == SCALAR_VALUE) {
                        if (tnum_is_const(regs[insn->src_reg].var_off))
                                reg_set_min_max(&other_branch->regs[insn->dst_reg],
                                                dst_reg, regs[insn->src_reg].var_off.value,
                                                opcode);
                        else if (tnum_is_const(dst_reg->var_off))
                                reg_set_min_max_inv(&other_branch->regs[insn->src_reg],
                                                    &regs[insn->src_reg],
                                                    dst_reg->var_off.value, opcode);
                        else if (opcode == BPF_JEQ || opcode == BPF_JNE)
                                /* Comparing for equality, we can combine knowledge */
                                reg_combine_min_max(&other_branch->regs[insn->src_reg],
                                                    &other_branch->regs[insn->dst_reg],
                                                    &regs[insn->src_reg],
                                                    &regs[insn->dst_reg], opcode);
                }
        } else if (dst_reg->type == SCALAR_VALUE) {
                reg_set_min_max(&other_branch->regs[insn->dst_reg],
                                        dst_reg, insn->imm, opcode);
        }

        /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */
        if (BPF_SRC(insn->code) == BPF_K &&
            insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
            dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
                /* Mark all identical map registers in each branch as either
                 * safe or unknown depending R == 0 or R != 0 conditional.
                 */
                mark_map_regs(this_branch, insn->dst_reg, opcode == BPF_JNE);
                mark_map_regs(other_branch, insn->dst_reg, opcode == BPF_JEQ);
        } else if (!try_match_pkt_pointers(insn, dst_reg, &regs[insn->src_reg],
                                           this_branch, other_branch) &&
                   is_pointer_value(env, insn->dst_reg)) {
                verbose(env, "R%d pointer comparison prohibited\n",
                        insn->dst_reg);
                return -EACCES;
        }
        if (env->log.level)
                print_verifier_state(env, this_branch);
        return 0;
}

/* return the map pointer stored inside BPF_LD_IMM64 instruction */
static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
{
        u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;

        return (struct bpf_map *) (unsigned long) imm64;
}

/* verify BPF_LD_IMM64 instruction */
static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        struct bpf_reg_state *regs = cur_regs(env);
        int err;

        if (BPF_SIZE(insn->code) != BPF_DW) {
                verbose(env, "invalid BPF_LD_IMM insn\n");
                return -EINVAL;
        }
        if (insn->off != 0) {
                verbose(env, "BPF_LD_IMM64 uses reserved fields\n");
                return -EINVAL;
        }

        err = check_reg_arg(env, insn->dst_reg, DST_OP);
        if (err)
                return err;

        if (insn->src_reg == 0) {
                u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;

                regs[insn->dst_reg].type = SCALAR_VALUE;
                __mark_reg_known(&regs[insn->dst_reg], imm);
                return 0;
        }

        /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
        BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);

        regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
        regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
        return 0;
}

static bool may_access_skb(enum bpf_prog_type type)
{
        switch (type) {
        case BPF_PROG_TYPE_SOCKET_FILTER:
        case BPF_PROG_TYPE_SCHED_CLS:
        case BPF_PROG_TYPE_SCHED_ACT:
                return true;
        default:
                return false;
        }
}

/* verify safety of LD_ABS|LD_IND instructions:
 * - they can only appear in the programs where ctx == skb
 * - since they are wrappers of function calls, they scratch R1-R5 registers,
 *   preserve R6-R9, and store return value into R0
 *
 * Implicit input:
 *   ctx == skb == R6 == CTX
 *
 * Explicit input:
 *   SRC == any register
 *   IMM == 32-bit immediate
 *
 * Output:
 *   R0 - 8/16/32-bit skb data converted to cpu endianness
 */
static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        struct bpf_reg_state *regs = cur_regs(env);
        u8 mode = BPF_MODE(insn->code);
        int i, err;

        if (!may_access_skb(env->prog->type)) {
                verbose(env, "BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
                return -EINVAL;
        }

        if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
            BPF_SIZE(insn->code) == BPF_DW ||
            (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
                verbose(env, "BPF_LD_[ABS|IND] uses reserved fields\n");
                return -EINVAL;
        }

        /* check whether implicit source operand (register R6) is readable */
        err = check_reg_arg(env, BPF_REG_6, SRC_OP);
        if (err)
                return err;

        if (regs[BPF_REG_6].type != PTR_TO_CTX) {
                verbose(env,
                        "at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
                return -EINVAL;
        }

        if (mode == BPF_IND) {
                /* check explicit source operand */
                err = check_reg_arg(env, insn->src_reg, SRC_OP);
                if (err)
                        return err;
        }

        /* reset caller saved regs to unreadable */
        for (i = 0; i < CALLER_SAVED_REGS; i++) {
                mark_reg_not_init(env, regs, caller_saved[i]);
                check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
        }

        /* mark destination R0 register as readable, since it contains
         * the value fetched from the packet.
         * Already marked as written above.
         */
        mark_reg_unknown(env, regs, BPF_REG_0);
        return 0;
}

static int check_return_code(struct bpf_verifier_env *env)
{
        struct bpf_reg_state *reg;
        struct tnum range = tnum_range(0, 1);

        switch (env->prog->type) {
        case BPF_PROG_TYPE_CGROUP_SKB:
        case BPF_PROG_TYPE_CGROUP_SOCK:
        case BPF_PROG_TYPE_SOCK_OPS:
        case BPF_PROG_TYPE_CGROUP_DEVICE:
                break;
        default:
                return 0;
        }

        reg = cur_regs(env) + BPF_REG_0;
        if (reg->type != SCALAR_VALUE) {
                verbose(env, "At program exit the register R0 is not a known value (%s)\n",
                        reg_type_str[reg->type]);
                return -EINVAL;
        }

        if (!tnum_in(range, reg->var_off)) {
                verbose(env, "At program exit the register R0 ");
                if (!tnum_is_unknown(reg->var_off)) {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                        verbose(env, "has value %s", tn_buf);
                } else {
                        verbose(env, "has unknown scalar value");
                }
                verbose(env, " should have been 0 or 1\n");
                return -EINVAL;
        }
        return 0;
}

/* non-recursive DFS pseudo code
 * 1  procedure DFS-iterative(G,v):
 * 2      label v as discovered
 * 3      let S be a stack
 * 4      S.push(v)
 * 5      while S is not empty
 * 6            t <- S.pop()
 * 7            if t is what we're looking for:
 * 8                return t
 * 9            for all edges e in G.adjacentEdges(t) do
 * 10               if edge e is already labelled
 * 11                   continue with the next edge
 * 12               w <- G.adjacentVertex(t,e)
 * 13               if vertex w is not discovered and not explored
 * 14                   label e as tree-edge
 * 15                   label w as discovered
 * 16                   S.push(w)
 * 17                   continue at 5
 * 18               else if vertex w is discovered
 * 19                   label e as back-edge
 * 20               else
 * 21                   // vertex w is explored
 * 22                   label e as forward- or cross-edge
 * 23           label t as explored
 * 24           S.pop()
 *
 * convention:
 * 0x10 - discovered
 * 0x11 - discovered and fall-through edge labelled
 * 0x12 - discovered and fall-through and branch edges labelled
 * 0x20 - explored
 */

enum {
        DISCOVERED = 0x10,
        EXPLORED = 0x20,
        FALLTHROUGH = 1,
        BRANCH = 2,
};

#define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L)

static int *insn_stack; /* stack of insns to process */
static int cur_stack;   /* current stack index */
static int *insn_state;

/* t, w, e - match pseudo-code above:
 * t - index of current instruction
 * w - next instruction
 * e - edge
 */
static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
{
        if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
                return 0;

        if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
                return 0;

        if (w < 0 || w >= env->prog->len) {
                verbose(env, "jump out of range from insn %d to %d\n", t, w);
                return -EINVAL;
        }

        if (e == BRANCH)
                /* mark branch target for state pruning */
                env->explored_states[w] = STATE_LIST_MARK;

        if (insn_state[w] == 0) {
                /* tree-edge */
                insn_state[t] = DISCOVERED | e;
                insn_state[w] = DISCOVERED;
                if (cur_stack >= env->prog->len)
                        return -E2BIG;
                insn_stack[cur_stack++] = w;
                return 1;
        } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
                verbose(env, "back-edge from insn %d to %d\n", t, w);
                return -EINVAL;
        } else if (insn_state[w] == EXPLORED) {
                /* forward- or cross-edge */
                insn_state[t] = DISCOVERED | e;
        } else {
                verbose(env, "insn state internal bug\n");
                return -EFAULT;
        }
        return 0;
}

/* non-recursive depth-first-search to detect loops in BPF program
 * loop == back-edge in directed graph
 */
static int check_cfg(struct bpf_verifier_env *env)
{
        struct bpf_insn *insns = env->prog->insnsi;
        int insn_cnt = env->prog->len;
        int ret = 0;
        int i, t;

        insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
        if (!insn_state)
                return -ENOMEM;

        insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
        if (!insn_stack) {
                kfree(insn_state);
                return -ENOMEM;
        }

        insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
        insn_stack[0] = 0; /* 0 is the first instruction */
        cur_stack = 1;

peek_stack:
        if (cur_stack == 0)
                goto check_state;
        t = insn_stack[cur_stack - 1];

        if (BPF_CLASS(insns[t].code) == BPF_JMP) {
                u8 opcode = BPF_OP(insns[t].code);

                if (opcode == BPF_EXIT) {
                        goto mark_explored;
                } else if (opcode == BPF_CALL) {
                        ret = push_insn(t, t + 1, FALLTHROUGH, env);
                        if (ret == 1)
                                goto peek_stack;
                        else if (ret < 0)
                                goto err_free;
                        if (t + 1 < insn_cnt)
                                env->explored_states[t + 1] = STATE_LIST_MARK;
                } else if (opcode == BPF_JA) {
                        if (BPF_SRC(insns[t].code) != BPF_K) {
                                ret = -EINVAL;
                                goto err_free;
                        }
                        /* unconditional jump with single edge */
                        ret = push_insn(t, t + insns[t].off + 1,
                                        FALLTHROUGH, env);
                        if (ret == 1)
                                goto peek_stack;
                        else if (ret < 0)
                                goto err_free;
                        /* tell verifier to check for equivalent states
                         * after every call and jump
                         */
                        if (t + 1 < insn_cnt)
                                env->explored_states[t + 1] = STATE_LIST_MARK;
                } else {
                        /* conditional jump with two edges */
                        env->explored_states[t] = STATE_LIST_MARK;
                        ret = push_insn(t, t + 1, FALLTHROUGH, env);
                        if (ret == 1)
                                goto peek_stack;
                        else if (ret < 0)
                                goto err_free;

                        ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
                        if (ret == 1)
                                goto peek_stack;
                        else if (ret < 0)
                                goto err_free;
                }
        } else {
                /* all other non-branch instructions with single
                 * fall-through edge
                 */
                ret = push_insn(t, t + 1, FALLTHROUGH, env);
                if (ret == 1)
                        goto peek_stack;
                else if (ret < 0)
                        goto err_free;
        }

mark_explored:
        insn_state[t] = EXPLORED;
        if (cur_stack-- <= 0) {
                verbose(env, "pop stack internal bug\n");
                ret = -EFAULT;
                goto err_free;
        }
        goto peek_stack;

check_state:
        for (i = 0; i < insn_cnt; i++) {
                if (insn_state[i] != EXPLORED) {
                        verbose(env, "unreachable insn %d\n", i);
                        ret = -EINVAL;
                        goto err_free;
                }
        }
        ret = 0; /* cfg looks good */

err_free:
        kfree(insn_state);
        kfree(insn_stack);
        return ret;
}

/* check %cur's range satisfies %old's */
static bool range_within(struct bpf_reg_state *old,
                         struct bpf_reg_state *cur)
{
        return old->umin_value <= cur->umin_value &&
               old->umax_value >= cur->umax_value &&
               old->smin_value <= cur->smin_value &&
               old->smax_value >= cur->smax_value;
}

/* Maximum number of register states that can exist at once */
#define ID_MAP_SIZE     (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
struct idpair {
        u32 old;
        u32 cur;
};

/* If in the old state two registers had the same id, then they need to have
 * the same id in the new state as well.  But that id could be different from
 * the old state, so we need to track the mapping from old to new ids.
 * Once we have seen that, say, a reg with old id 5 had new id 9, any subsequent
 * regs with old id 5 must also have new id 9 for the new state to be safe.  But
 * regs with a different old id could still have new id 9, we don't care about
 * that.
 * So we look through our idmap to see if this old id has been seen before.  If
 * so, we require the new id to match; otherwise, we add the id pair to the map.
 */
static bool check_ids(u32 old_id, u32 cur_id, struct idpair *idmap)
{
        unsigned int i;

        for (i = 0; i < ID_MAP_SIZE; i++) {
                if (!idmap[i].old) {
                        /* Reached an empty slot; haven't seen this id before */
                        idmap[i].old = old_id;
                        idmap[i].cur = cur_id;
                        return true;
                }
                if (idmap[i].old == old_id)
                        return idmap[i].cur == cur_id;
        }
        /* We ran out of idmap slots, which should be impossible */
        WARN_ON_ONCE(1);
        return false;
}

/* Returns true if (rold safe implies rcur safe) */
static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
                    struct idpair *idmap)
{
        if (!(rold->live & REG_LIVE_READ))
                /* explored state didn't use this */
                return true;

        if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, live)) == 0)
                return true;

        if (rold->type == NOT_INIT)
                /* explored state can't have used this */
                return true;
        if (rcur->type == NOT_INIT)
                return false;
        switch (rold->type) {
        case SCALAR_VALUE:
                if (rcur->type == SCALAR_VALUE) {
                        /* new val must satisfy old val knowledge */
                        return range_within(rold, rcur) &&
                               tnum_in(rold->var_off, rcur->var_off);
                } else {
                        /* We're trying to use a pointer in place of a scalar.
                         * Even if the scalar was unbounded, this could lead to
                         * pointer leaks because scalars are allowed to leak
                         * while pointers are not. We could make this safe in
                         * special cases if root is calling us, but it's
                         * probably not worth the hassle.
                         */
                        return false;
                }
        case PTR_TO_MAP_VALUE:
                /* If the new min/max/var_off satisfy the old ones and
                 * everything else matches, we are OK.
                 * We don't care about the 'id' value, because nothing
                 * uses it for PTR_TO_MAP_VALUE (only for ..._OR_NULL)
                 */
                return memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)) == 0 &&
                       range_within(rold, rcur) &&
                       tnum_in(rold->var_off, rcur->var_off);
        case PTR_TO_MAP_VALUE_OR_NULL:
                /* a PTR_TO_MAP_VALUE could be safe to use as a
                 * PTR_TO_MAP_VALUE_OR_NULL into the same map.
                 * However, if the old PTR_TO_MAP_VALUE_OR_NULL then got NULL-
                 * checked, doing so could have affected others with the same
                 * id, and we can't check for that because we lost the id when
                 * we converted to a PTR_TO_MAP_VALUE.
                 */
                if (rcur->type != PTR_TO_MAP_VALUE_OR_NULL)
                        return false;
                if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)))
                        return false;
                /* Check our ids match any regs they're supposed to */
                return check_ids(rold->id, rcur->id, idmap);
        case PTR_TO_PACKET_META:
        case PTR_TO_PACKET:
                if (rcur->type != rold->type)
                        return false;
                /* We must have at least as much range as the old ptr
                 * did, so that any accesses which were safe before are
                 * still safe.  This is true even if old range < old off,
                 * since someone could have accessed through (ptr - k), or
                 * even done ptr -= k in a register, to get a safe access.
                 */
                if (rold->range > rcur->range)
                        return false;
                /* If the offsets don't match, we can't trust our alignment;
                 * nor can we be sure that we won't fall out of range.
                 */
                if (rold->off != rcur->off)
                        return false;
                /* id relations must be preserved */
                if (rold->id && !check_ids(rold->id, rcur->id, idmap))
                        return false;
                /* new val must satisfy old val knowledge */
                return range_within(rold, rcur) &&
                       tnum_in(rold->var_off, rcur->var_off);
        case PTR_TO_CTX:
        case CONST_PTR_TO_MAP:
        case PTR_TO_STACK:
        case PTR_TO_PACKET_END:
                /* Only valid matches are exact, which memcmp() above
                 * would have accepted
                 */
        default:
                /* Don't know what's going on, just say it's not safe */
                return false;
        }

        /* Shouldn't get here; if we do, say it's not safe */
        WARN_ON_ONCE(1);
        return false;
}

static bool stacksafe(struct bpf_verifier_state *old,
                      struct bpf_verifier_state *cur,
                      struct idpair *idmap)
{
        int i, spi;

        /* if explored stack has more populated slots than current stack
         * such stacks are not equivalent
         */
        if (old->allocated_stack > cur->allocated_stack)
                return false;

        /* walk slots of the explored stack and ignore any additional
         * slots in the current stack, since explored(safe) state
         * didn't use them
         */
        for (i = 0; i < old->allocated_stack; i++) {
                spi = i / BPF_REG_SIZE;

                if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID)
                        continue;
                if (old->stack[spi].slot_type[i % BPF_REG_SIZE] !=
                    cur->stack[spi].slot_type[i % BPF_REG_SIZE])
                        /* Ex: old explored (safe) state has STACK_SPILL in
                         * this stack slot, but current has has STACK_MISC ->
                         * this verifier states are not equivalent,
                         * return false to continue verification of this path
                         */
                        return false;
                if (i % BPF_REG_SIZE)
                        continue;
                if (old->stack[spi].slot_type[0] != STACK_SPILL)
                        continue;
                if (!regsafe(&old->stack[spi].spilled_ptr,
                             &cur->stack[spi].spilled_ptr,
                             idmap))
                        /* when explored and current stack slot are both storing
                         * spilled registers, check that stored pointers types
                         * are the same as well.
                         * Ex: explored safe path could have stored
                         * (bpf_reg_state) {.type = PTR_TO_STACK, .off = -8}
                         * but current path has stored:
                         * (bpf_reg_state) {.type = PTR_TO_STACK, .off = -16}
                         * such verifier states are not equivalent.
                         * return false to continue verification of this path
                         */
                        return false;
        }
        return true;
}

/* compare two verifier states
 *
 * all states stored in state_list are known to be valid, since
 * verifier reached 'bpf_exit' instruction through them
 *
 * this function is called when verifier exploring different branches of
 * execution popped from the state stack. If it sees an old state that has
 * more strict register state and more strict stack state then this execution
 * branch doesn't need to be explored further, since verifier already
 * concluded that more strict state leads to valid finish.
 *
 * Therefore two states are equivalent if register state is more conservative
 * and explored stack state is more conservative than the current one.
 * Example:
 *       explored                   current
 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
 *
 * In other words if current stack state (one being explored) has more
 * valid slots than old one that already passed validation, it means
 * the verifier can stop exploring and conclude that current state is valid too
 *
 * Similarly with registers. If explored state has register type as invalid
 * whereas register type in current state is meaningful, it means that
 * the current state will reach 'bpf_exit' instruction safely
 */
static bool states_equal(struct bpf_verifier_env *env,
                         struct bpf_verifier_state *old,
                         struct bpf_verifier_state *cur)
{
        struct idpair *idmap;
        bool ret = false;
        int i;

        idmap = kcalloc(ID_MAP_SIZE, sizeof(struct idpair), GFP_KERNEL);
        /* If we failed to allocate the idmap, just say it's not safe */
        if (!idmap)
                return false;

        for (i = 0; i < MAX_BPF_REG; i++) {
                if (!regsafe(&old->regs[i], &cur->regs[i], idmap))
                        goto out_free;
        }

        if (!stacksafe(old, cur, idmap))
                goto out_free;
        ret = true;
out_free:
        kfree(idmap);
        return ret;
}

/* A write screens off any subsequent reads; but write marks come from the
 * straight-line code between a state and its parent.  When we arrive at a
 * jump target (in the first iteration of the propagate_liveness() loop),
 * we didn't arrive by the straight-line code, so read marks in state must
 * propagate to parent regardless of state's write marks.
 */
static bool do_propagate_liveness(const struct bpf_verifier_state *state,
                                  struct bpf_verifier_state *parent)
{
        bool writes = parent == state->parent; /* Observe write marks */
        bool touched = false; /* any changes made? */
        int i;

        if (!parent)
                return touched;
        /* Propagate read liveness of registers... */
        BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
        /* We don't need to worry about FP liveness because it's read-only */
        for (i = 0; i < BPF_REG_FP; i++) {
                if (parent->regs[i].live & REG_LIVE_READ)
                        continue;
                if (writes && (state->regs[i].live & REG_LIVE_WRITTEN))
                        continue;
                if (state->regs[i].live & REG_LIVE_READ) {
                        parent->regs[i].live |= REG_LIVE_READ;
                        touched = true;
                }
        }
        /* ... and stack slots */
        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE &&
                    i < parent->allocated_stack / BPF_REG_SIZE; i++) {
                if (parent->stack[i].slot_type[0] != STACK_SPILL)
                        continue;
                if (state->stack[i].slot_type[0] != STACK_SPILL)
                        continue;
                if (parent->stack[i].spilled_ptr.live & REG_LIVE_READ)
                        continue;
                if (writes &&
                    (state->stack[i].spilled_ptr.live & REG_LIVE_WRITTEN))
                        continue;
                if (state->stack[i].spilled_ptr.live & REG_LIVE_READ) {
                        parent->stack[i].spilled_ptr.live |= REG_LIVE_READ;
                        touched = true;
                }
        }
        return touched;
}

/* "parent" is "a state from which we reach the current state", but initially
 * it is not the state->parent (i.e. "the state whose straight-line code leads
 * to the current state"), instead it is the state that happened to arrive at
 * a (prunable) equivalent of the current state.  See comment above
 * do_propagate_liveness() for consequences of this.
 * This function is just a more efficient way of calling mark_reg_read() or
 * mark_stack_slot_read() on each reg in "parent" that is read in "state",
 * though it requires that parent != state->parent in the call arguments.
 */
static void propagate_liveness(const struct bpf_verifier_state *state,
                               struct bpf_verifier_state *parent)
{
        while (do_propagate_liveness(state, parent)) {
                /* Something changed, so we need to feed those changes onward */
                state = parent;
                parent = state->parent;
        }
}

static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
{
        struct bpf_verifier_state_list *new_sl;
        struct bpf_verifier_state_list *sl;
        struct bpf_verifier_state *cur = env->cur_state;
        int i, err;

        sl = env->explored_states[insn_idx];
        if (!sl)
                /* this 'insn_idx' instruction wasn't marked, so we will not
                 * be doing state search here
                 */
                return 0;

        while (sl != STATE_LIST_MARK) {
                if (states_equal(env, &sl->state, cur)) {
                        /* reached equivalent register/stack state,
                         * prune the search.
                         * Registers read by the continuation are read by us.
                         * If we have any write marks in env->cur_state, they
                         * will prevent corresponding reads in the continuation
                         * from reaching our parent (an explored_state).  Our
                         * own state will get the read marks recorded, but
                         * they'll be immediately forgotten as we're pruning
                         * this state and will pop a new one.
                         */
                        propagate_liveness(&sl->state, cur);
                        return 1;
                }
                sl = sl->next;
        }

        /* there were no equivalent states, remember current one.
         * technically the current state is not proven to be safe yet,
         * but it will either reach bpf_exit (which means it's safe) or
         * it will be rejected. Since there are no loops, we won't be
         * seeing this 'insn_idx' instruction again on the way to bpf_exit
         */
        new_sl = kzalloc(sizeof(struct bpf_verifier_state_list), GFP_KERNEL);
        if (!new_sl)
                return -ENOMEM;

        /* add new state to the head of linked list */
        err = copy_verifier_state(&new_sl->state, cur);
        if (err) {
                free_verifier_state(&new_sl->state, false);
                kfree(new_sl);
                return err;
        }
        new_sl->next = env->explored_states[insn_idx];
        env->explored_states[insn_idx] = new_sl;
        /* connect new state to parentage chain */
        cur->parent = &new_sl->state;
        /* clear write marks in current state: the writes we did are not writes
         * our child did, so they don't screen off its reads from us.
         * (There are no read marks in current state, because reads always mark
         * their parent and current state never has children yet.  Only
         * explored_states can get read marks.)
         */
        for (i = 0; i < BPF_REG_FP; i++)
                cur->regs[i].live = REG_LIVE_NONE;
        for (i = 0; i < cur->allocated_stack / BPF_REG_SIZE; i++)
                if (cur->stack[i].slot_type[0] == STACK_SPILL)
                        cur->stack[i].spilled_ptr.live = REG_LIVE_NONE;
        return 0;
}

static int ext_analyzer_insn_hook(struct bpf_verifier_env *env,
                                  int insn_idx, int prev_insn_idx)
{
        if (env->dev_ops && env->dev_ops->insn_hook)
                return env->dev_ops->insn_hook(env, insn_idx, prev_insn_idx);

        return 0;
}

static int do_check(struct bpf_verifier_env *env)
{
        struct bpf_verifier_state *state;
        struct bpf_insn *insns = env->prog->insnsi;
        struct bpf_reg_state *regs;
        int insn_cnt = env->prog->len;
        int insn_idx, prev_insn_idx = 0;
        int insn_processed = 0;
        bool do_print_state = false;

        state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL);
        if (!state)
                return -ENOMEM;
        env->cur_state = state;
        init_reg_state(env, state->regs);
        state->parent = NULL;
        insn_idx = 0;
        for (;;) {
                struct bpf_insn *insn;
                u8 class;
                int err;

                if (insn_idx >= insn_cnt) {
                        verbose(env, "invalid insn idx %d insn_cnt %d\n",
                                insn_idx, insn_cnt);
                        return -EFAULT;
                }

                insn = &insns[insn_idx];
                class = BPF_CLASS(insn->code);

                if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
                        verbose(env,
                                "BPF program is too large. Processed %d insn\n",
                                insn_processed);
                        return -E2BIG;
                }

                err = is_state_visited(env, insn_idx);
                if (err < 0)
                        return err;
                if (err == 1) {
                        /* found equivalent state, can prune the search */
                        if (env->log.level) {
                                if (do_print_state)
                                        verbose(env, "\nfrom %d to %d: safe\n",
                                                prev_insn_idx, insn_idx);
                                else
                                        verbose(env, "%d: safe\n", insn_idx);
                        }
                        goto process_bpf_exit;
                }

                if (need_resched())
                        cond_resched();

                if (env->log.level > 1 || (env->log.level && do_print_state)) {
                        if (env->log.level > 1)
                                verbose(env, "%d:", insn_idx);
                        else
                                verbose(env, "\nfrom %d to %d:",
                                        prev_insn_idx, insn_idx);
                        print_verifier_state(env, state);
                        do_print_state = false;
                }

                if (env->log.level) {
                        verbose(env, "%d: ", insn_idx);
                        print_bpf_insn(verbose, env, insn,
                                       env->allow_ptr_leaks);
                }

                err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx);
                if (err)
                        return err;

                regs = cur_regs(env);
                env->insn_aux_data[insn_idx].seen = true;
                if (class == BPF_ALU || class == BPF_ALU64) {
                        err = check_alu_op(env, insn);
                        if (err)
                                return err;

                } else if (class == BPF_LDX) {
                        enum bpf_reg_type *prev_src_type, src_reg_type;

                        /* check for reserved fields is already done */

                        /* check src operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;

                        err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
                        if (err)
                                return err;

                        src_reg_type = regs[insn->src_reg].type;

                        /* check that memory (src_reg + off) is readable,
                         * the state of dst_reg will be updated by this func
                         */
                        err = check_mem_access(env, insn_idx, insn->src_reg, insn->off,
                                               BPF_SIZE(insn->code), BPF_READ,
                                               insn->dst_reg);
                        if (err)
                                return err;

                        prev_src_type = &env->insn_aux_data[insn_idx].ptr_type;

                        if (*prev_src_type == NOT_INIT) {
                                /* saw a valid insn
                                 * dst_reg = *(u32 *)(src_reg + off)
                                 * save type to validate intersecting paths
                                 */
                                *prev_src_type = src_reg_type;

                        } else if (src_reg_type != *prev_src_type &&
                                   (src_reg_type == PTR_TO_CTX ||
                                    *prev_src_type == PTR_TO_CTX)) {
                                /* ABuser program is trying to use the same insn
                                 * dst_reg = *(u32*) (src_reg + off)
                                 * with different pointer types:
                                 * src_reg == ctx in one branch and
                                 * src_reg == stack|map in some other branch.
                                 * Reject it.
                                 */
                                verbose(env, "same insn cannot be used with different pointers\n");
                                return -EINVAL;
                        }

                } else if (class == BPF_STX) {
                        enum bpf_reg_type *prev_dst_type, dst_reg_type;

                        if (BPF_MODE(insn->code) == BPF_XADD) {
                                err = check_xadd(env, insn_idx, insn);
                                if (err)
                                        return err;
                                insn_idx++;
                                continue;
                        }

                        /* check src1 operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;
                        /* check src2 operand */
                        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                        if (err)
                                return err;

                        dst_reg_type = regs[insn->dst_reg].type;

                        /* check that memory (dst_reg + off) is writeable */
                        err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
                                               BPF_SIZE(insn->code), BPF_WRITE,
                                               insn->src_reg);
                        if (err)
                                return err;

                        prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type;

                        if (*prev_dst_type == NOT_INIT) {
                                *prev_dst_type = dst_reg_type;
                        } else if (dst_reg_type != *prev_dst_type &&
                                   (dst_reg_type == PTR_TO_CTX ||
                                    *prev_dst_type == PTR_TO_CTX)) {
                                verbose(env, "same insn cannot be used with different pointers\n");
                                return -EINVAL;
                        }

                } else if (class == BPF_ST) {
                        if (BPF_MODE(insn->code) != BPF_MEM ||
                            insn->src_reg != BPF_REG_0) {
                                verbose(env, "BPF_ST uses reserved fields\n");
                                return -EINVAL;
                        }
                        /* check src operand */
                        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                        if (err)
                                return err;

                        if (is_ctx_reg(env, insn->dst_reg)) {
                                verbose(env, "BPF_ST stores into R%d context is not allowed\n",
                                        insn->dst_reg);
                                return -EACCES;
                        }

                        /* check that memory (dst_reg + off) is writeable */
                        err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
                                               BPF_SIZE(insn->code), BPF_WRITE,
                                               -1);
                        if (err)
                                return err;

                } else if (class == BPF_JMP) {
                        u8 opcode = BPF_OP(insn->code);

                        if (opcode == BPF_CALL) {
                                if (BPF_SRC(insn->code) != BPF_K ||
                                    insn->off != 0 ||
                                    insn->src_reg != BPF_REG_0 ||
                                    insn->dst_reg != BPF_REG_0) {
                                        verbose(env, "BPF_CALL uses reserved fields\n");
                                        return -EINVAL;
                                }

                                err = check_call(env, insn->imm, insn_idx);
                                if (err)
                                        return err;

                        } else if (opcode == BPF_JA) {
                                if (BPF_SRC(insn->code) != BPF_K ||
                                    insn->imm != 0 ||
                                    insn->src_reg != BPF_REG_0 ||
                                    insn->dst_reg != BPF_REG_0) {
                                        verbose(env, "BPF_JA uses reserved fields\n");
                                        return -EINVAL;
                                }

                                insn_idx += insn->off + 1;
                                continue;

                        } else if (opcode == BPF_EXIT) {
                                if (BPF_SRC(insn->code) != BPF_K ||
                                    insn->imm != 0 ||
                                    insn->src_reg != BPF_REG_0 ||
                                    insn->dst_reg != BPF_REG_0) {
                                        verbose(env, "BPF_EXIT uses reserved fields\n");
                                        return -EINVAL;
                                }

                                /* eBPF calling convetion is such that R0 is used
                                 * to return the value from eBPF program.
                                 * Make sure that it's readable at this time
                                 * of bpf_exit, which means that program wrote
                                 * something into it earlier
                                 */
                                err = check_reg_arg(env, BPF_REG_0, SRC_OP);
                                if (err)
                                        return err;

                                if (is_pointer_value(env, BPF_REG_0)) {
                                        verbose(env, "R0 leaks addr as return value\n");
                                        return -EACCES;
                                }

                                err = check_return_code(env);
                                if (err)
                                        return err;
process_bpf_exit:
                                err = pop_stack(env, &prev_insn_idx, &insn_idx);
                                if (err < 0) {
                                        if (err != -ENOENT)
                                                return err;
                                        break;
                                } else {
                                        do_print_state = true;
                                        continue;
                                }
                        } else {
                                err = check_cond_jmp_op(env, insn, &insn_idx);
                                if (err)
                                        return err;
                        }
                } else if (class == BPF_LD) {
                        u8 mode = BPF_MODE(insn->code);

                        if (mode == BPF_ABS || mode == BPF_IND) {
                                err = check_ld_abs(env, insn);
                                if (err)
                                        return err;

                        } else if (mode == BPF_IMM) {
                                err = check_ld_imm(env, insn);
                                if (err)
                                        return err;

                                insn_idx++;
                                env->insn_aux_data[insn_idx].seen = true;
                        } else {
                                verbose(env, "invalid BPF_LD mode\n");
                                return -EINVAL;
                        }
                } else {
                        verbose(env, "unknown insn class %d\n", class);
                        return -EINVAL;
                }

                insn_idx++;
        }

        verbose(env, "processed %d insns, stack depth %d\n", insn_processed,
                env->prog->aux->stack_depth);
        return 0;
}

static int check_map_prealloc(struct bpf_map *map)
{
        return (map->map_type != BPF_MAP_TYPE_HASH &&
                map->map_type != BPF_MAP_TYPE_PERCPU_HASH &&
                map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) ||
                !(map->map_flags & BPF_F_NO_PREALLOC);
}

static int check_map_prog_compatibility(struct bpf_verifier_env *env,
                                        struct bpf_map *map,
                                        struct bpf_prog *prog)

{
        /* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use
         * preallocated hash maps, since doing memory allocation
         * in overflow_handler can crash depending on where nmi got
         * triggered.
         */
        if (prog->type == BPF_PROG_TYPE_PERF_EVENT) {
                if (!check_map_prealloc(map)) {
                        verbose(env, "perf_event programs can only use preallocated hash map\n");
                        return -EINVAL;
                }
                if (map->inner_map_meta &&
                    !check_map_prealloc(map->inner_map_meta)) {
                        verbose(env, "perf_event programs can only use preallocated inner hash map\n");
                        return -EINVAL;
                }
        }
        return 0;
}

/* look for pseudo eBPF instructions that access map FDs and
 * replace them with actual map pointers
 */
static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env)
{
        struct bpf_insn *insn = env->prog->insnsi;
        int insn_cnt = env->prog->len;
        int i, j, err;

        err = bpf_prog_calc_tag(env->prog);
        if (err)
                return err;

        for (i = 0; i < insn_cnt; i++, insn++) {
                if (BPF_CLASS(insn->code) == BPF_LDX &&
                    (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
                        verbose(env, "BPF_LDX uses reserved fields\n");
                        return -EINVAL;
                }

                if (BPF_CLASS(insn->code) == BPF_STX &&
                    ((BPF_MODE(insn->code) != BPF_MEM &&
                      BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
                        verbose(env, "BPF_STX uses reserved fields\n");
                        return -EINVAL;
                }

                if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
                        struct bpf_map *map;
                        struct fd f;

                        if (i == insn_cnt - 1 || insn[1].code != 0 ||
                            insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
                            insn[1].off != 0) {
                                verbose(env, "invalid bpf_ld_imm64 insn\n");
                                return -EINVAL;
                        }

                        if (insn->src_reg == 0)
                                /* valid generic load 64-bit imm */
                                goto next_insn;

                        if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
                                verbose(env,
                                        "unrecognized bpf_ld_imm64 insn\n");
                                return -EINVAL;
                        }

                        f = fdget(insn->imm);
                        map = __bpf_map_get(f);
                        if (IS_ERR(map)) {
                                verbose(env, "fd %d is not pointing to valid bpf_map\n",
                                        insn->imm);
                                return PTR_ERR(map);
                        }

                        err = check_map_prog_compatibility(env, map, env->prog);
                        if (err) {
                                fdput(f);
                                return err;
                        }

                        /* store map pointer inside BPF_LD_IMM64 instruction */
                        insn[0].imm = (u32) (unsigned long) map;
                        insn[1].imm = ((u64) (unsigned long) map) >> 32;

                        /* check whether we recorded this map already */
                        for (j = 0; j < env->used_map_cnt; j++)
                                if (env->used_maps[j] == map) {
                                        fdput(f);
                                        goto next_insn;
                                }

                        if (env->used_map_cnt >= MAX_USED_MAPS) {
                                fdput(f);
                                return -E2BIG;
                        }

                        /* hold the map. If the program is rejected by verifier,
                         * the map will be released by release_maps() or it
                         * will be used by the valid program until it's unloaded
                         * and all maps are released in free_bpf_prog_info()
                         */
                        map = bpf_map_inc(map, false);
                        if (IS_ERR(map)) {
                                fdput(f);
                                return PTR_ERR(map);
                        }
                        env->used_maps[env->used_map_cnt++] = map;

                        fdput(f);
next_insn:
                        insn++;
                        i++;
                }
        }

        /* now all pseudo BPF_LD_IMM64 instructions load valid
         * 'struct bpf_map *' into a register instead of user map_fd.
         * These pointers will be used later by verifier to validate map access.
         */
        return 0;
}

/* drop refcnt of maps used by the rejected program */
static void release_maps(struct bpf_verifier_env *env)
{
        int i;

        for (i = 0; i < env->used_map_cnt; i++)
                bpf_map_put(env->used_maps[i]);
}

/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
{
        struct bpf_insn *insn = env->prog->insnsi;
        int insn_cnt = env->prog->len;
        int i;

        for (i = 0; i < insn_cnt; i++, insn++)
                if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
                        insn->src_reg = 0;
}

/* single env->prog->insni[off] instruction was replaced with the range
 * insni[off, off + cnt).  Adjust corresponding insn_aux_data by copying
 * [0, off) and [off, end) to new locations, so the patched range stays zero
 */
static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len,
                                u32 off, u32 cnt)
{
        struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
        int i;

        if (cnt == 1)
                return 0;
        new_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog_len);
        if (!new_data)
                return -ENOMEM;
        memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
        memcpy(new_data + off + cnt - 1, old_data + off,
               sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
        for (i = off; i < off + cnt - 1; i++)
                new_data[i].seen = true;
        env->insn_aux_data = new_data;
        vfree(old_data);
        return 0;
}

static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
                                            const struct bpf_insn *patch, u32 len)
{
        struct bpf_prog *new_prog;

        new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
        if (!new_prog)
                return NULL;
        if (adjust_insn_aux_data(env, new_prog->len, off, len))
                return NULL;
        return new_prog;
}

/* The verifier does more data flow analysis than llvm and will not explore
 * branches that are dead at run time. Malicious programs can have dead code
 * too. Therefore replace all dead at-run-time code with nops.
 */
static void sanitize_dead_code(struct bpf_verifier_env *env)
{
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        struct bpf_insn nop = BPF_MOV64_REG(BPF_REG_0, BPF_REG_0);
        struct bpf_insn *insn = env->prog->insnsi;
        const int insn_cnt = env->prog->len;
        int i;

        for (i = 0; i < insn_cnt; i++) {
                if (aux_data[i].seen)
                        continue;
                memcpy(insn + i, &nop, sizeof(nop));
        }
}

/* convert load instructions that access fields of 'struct __sk_buff'
 * into sequence of instructions that access fields of 'struct sk_buff'
 */
static int convert_ctx_accesses(struct bpf_verifier_env *env)
{
        const struct bpf_verifier_ops *ops = env->ops;
        int i, cnt, size, ctx_field_size, delta = 0;
        const int insn_cnt = env->prog->len;
        struct bpf_insn insn_buf[16], *insn;
        struct bpf_prog *new_prog;
        enum bpf_access_type type;
        bool is_narrower_load;
        u32 target_size;

        if (ops->gen_prologue) {
                cnt = ops->gen_prologue(insn_buf, env->seen_direct_write,
                                        env->prog);
                if (cnt >= ARRAY_SIZE(insn_buf)) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                } else if (cnt) {
                        new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        env->prog = new_prog;
                        delta += cnt - 1;
                }
        }

        if (!ops->convert_ctx_access)
                return 0;

        insn = env->prog->insnsi + delta;

        for (i = 0; i < insn_cnt; i++, insn++) {
                if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
                    insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
                    insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
                    insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
                        type = BPF_READ;
                else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
                         insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
                         insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
                         insn->code == (BPF_STX | BPF_MEM | BPF_DW))
                        type = BPF_WRITE;
                else
                        continue;

                if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX)
                        continue;

                ctx_field_size = env->insn_aux_data[i + delta].ctx_field_size;
                size = BPF_LDST_BYTES(insn);

                /* If the read access is a narrower load of the field,
                 * convert to a 4/8-byte load, to minimum program type specific
                 * convert_ctx_access changes. If conversion is successful,
                 * we will apply proper mask to the result.
                 */
                is_narrower_load = size < ctx_field_size;
                if (is_narrower_load) {
                        u32 off = insn->off;
                        u8 size_code;

                        if (type == BPF_WRITE) {
                                verbose(env, "bpf verifier narrow ctx access misconfigured\n");
                                return -EINVAL;
                        }

                        size_code = BPF_H;
                        if (ctx_field_size == 4)
                                size_code = BPF_W;
                        else if (ctx_field_size == 8)
                                size_code = BPF_DW;

                        insn->off = off & ~(ctx_field_size - 1);
                        insn->code = BPF_LDX | BPF_MEM | size_code;
                }

                target_size = 0;
                cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog,
                                              &target_size);
                if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf) ||
                    (ctx_field_size && !target_size)) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                }

                if (is_narrower_load && size < target_size) {
                        if (ctx_field_size <= 4)
                                insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg,
                                                                (1 << size * 8) - 1);
                        else
                                insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg,
                                                                (1 << size * 8) - 1);
                }

                new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                if (!new_prog)
                        return -ENOMEM;

                delta += cnt - 1;

                /* keep walking new program and skip insns we just inserted */
                env->prog = new_prog;
                insn      = new_prog->insnsi + i + delta;
        }

        return 0;
}

/* fixup insn->imm field of bpf_call instructions
 * and inline eligible helpers as explicit sequence of BPF instructions
 *
 * this function is called after eBPF program passed verification
 */
static int fixup_bpf_calls(struct bpf_verifier_env *env)
{
        struct bpf_prog *prog = env->prog;
        struct bpf_insn *insn = prog->insnsi;
        const struct bpf_func_proto *fn;
        const int insn_cnt = prog->len;
        struct bpf_insn insn_buf[16];
        struct bpf_prog *new_prog;
        struct bpf_map *map_ptr;
        int i, cnt, delta = 0;

        for (i = 0; i < insn_cnt; i++, insn++) {
                if (insn->code == (BPF_ALU | BPF_MOD | BPF_X) ||
                    insn->code == (BPF_ALU | BPF_DIV | BPF_X)) {
                        /* due to JIT bugs clear upper 32-bits of src register
                         * before div/mod operation
                         */
                        insn_buf[0] = BPF_MOV32_REG(insn->src_reg, insn->src_reg);
                        insn_buf[1] = *insn;
                        cnt = 2;
                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                if (insn->code != (BPF_JMP | BPF_CALL))
                        continue;

                if (insn->imm == BPF_FUNC_get_route_realm)
                        prog->dst_needed = 1;
                if (insn->imm == BPF_FUNC_get_prandom_u32)
                        bpf_user_rnd_init_once();
                if (insn->imm == BPF_FUNC_tail_call) {
                        /* If we tail call into other programs, we
                         * cannot make any assumptions since they can
                         * be replaced dynamically during runtime in
                         * the program array.
                         */
                        prog->cb_access = 1;
                        env->prog->aux->stack_depth = MAX_BPF_STACK;

                        /* mark bpf_tail_call as different opcode to avoid
                         * conditional branch in the interpeter for every normal
                         * call and to prevent accidental JITing by JIT compiler
                         * that doesn't support bpf_tail_call yet
                         */
                        insn->imm = 0;
                        insn->code = BPF_JMP | BPF_TAIL_CALL;

                        /* instead of changing every JIT dealing with tail_call
                         * emit two extra insns:
                         * if (index >= max_entries) goto out;
                         * index &= array->index_mask;
                         * to avoid out-of-bounds cpu speculation
                         */
                        map_ptr = env->insn_aux_data[i + delta].map_ptr;
                        if (map_ptr == BPF_MAP_PTR_POISON) {
                                verbose(env, "tail_call abusing map_ptr\n");
                                return -EINVAL;
                        }
                        if (!map_ptr->unpriv_array)
                                continue;
                        insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3,
                                                  map_ptr->max_entries, 2);
                        insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3,
                                                    container_of(map_ptr,
                                                                 struct bpf_array,
                                                                 map)->index_mask);
                        insn_buf[2] = *insn;
                        cnt = 3;
                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                /* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup
                 * handlers are currently limited to 64 bit only.
                 */
                if (ebpf_jit_enabled() && BITS_PER_LONG == 64 &&
                    insn->imm == BPF_FUNC_map_lookup_elem) {
                        map_ptr = env->insn_aux_data[i + delta].map_ptr;
                        if (map_ptr == BPF_MAP_PTR_POISON ||
                            !map_ptr->ops->map_gen_lookup)
                                goto patch_call_imm;

                        cnt = map_ptr->ops->map_gen_lookup(map_ptr, insn_buf);
                        if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
                                verbose(env, "bpf verifier is misconfigured\n");
                                return -EINVAL;
                        }

                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf,
                                                       cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta += cnt - 1;

                        /* keep walking new program and skip insns we just inserted */
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                if (insn->imm == BPF_FUNC_redirect_map) {
                        /* Note, we cannot use prog directly as imm as subsequent
                         * rewrites would still change the prog pointer. The only
                         * stable address we can use is aux, which also works with
                         * prog clones during blinding.
                         */
                        u64 addr = (unsigned long)prog->aux;
                        struct bpf_insn r4_ld[] = {
                                BPF_LD_IMM64(BPF_REG_4, addr),
                                *insn,
                        };
                        cnt = ARRAY_SIZE(r4_ld);

                        new_prog = bpf_patch_insn_data(env, i + delta, r4_ld, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                }
patch_call_imm:
                fn = env->ops->get_func_proto(insn->imm);
                /* all functions that have prototype and verifier allowed
                 * programs to call them, must be real in-kernel functions
                 */
                if (!fn->func) {
                        verbose(env,
                                "kernel subsystem misconfigured func %s#%d\n",
                                func_id_name(insn->imm), insn->imm);
                        return -EFAULT;
                }
                insn->imm = fn->func - __bpf_call_base;
        }

        return 0;
}

static void free_states(struct bpf_verifier_env *env)
{
        struct bpf_verifier_state_list *sl, *sln;
        int i;

        if (!env->explored_states)
                return;

        for (i = 0; i < env->prog->len; i++) {
                sl = env->explored_states[i];

                if (sl)
                        while (sl != STATE_LIST_MARK) {
                                sln = sl->next;
                                free_verifier_state(&sl->state, false);
                                kfree(sl);
                                sl = sln;
                        }
        }

        kfree(env->explored_states);
}

int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
{
        struct bpf_verifier_env *env;
        struct bpf_verifer_log *log;
        int ret = -EINVAL;

        /* no program is valid */
        if (ARRAY_SIZE(bpf_verifier_ops) == 0)
                return -EINVAL;

        /* 'struct bpf_verifier_env' can be global, but since it's not small,
         * allocate/free it every time bpf_check() is called
         */
        env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
        if (!env)
                return -ENOMEM;
        log = &env->log;

        env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) *
                                     (*prog)->len);
        ret = -ENOMEM;
        if (!env->insn_aux_data)
                goto err_free_env;
        env->prog = *prog;
        env->ops = bpf_verifier_ops[env->prog->type];

        /* grab the mutex to protect few globals used by verifier */
        mutex_lock(&bpf_verifier_lock);

        if (attr->log_level || attr->log_buf || attr->log_size) {
                /* user requested verbose verifier output
                 * and supplied buffer to store the verification trace
                 */
                log->level = attr->log_level;
                log->ubuf = (char __user *) (unsigned long) attr->log_buf;
                log->len_total = attr->log_size;

                ret = -EINVAL;
                /* log attributes have to be sane */
                if (log->len_total < 128 || log->len_total > UINT_MAX >> 8 ||
                    !log->level || !log->ubuf)
                        goto err_unlock;
        }

        env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT);
        if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
                env->strict_alignment = true;

        if (env->prog->aux->offload) {
                ret = bpf_prog_offload_verifier_prep(env);
                if (ret)
                        goto err_unlock;
        }

        ret = replace_map_fd_with_map_ptr(env);
        if (ret < 0)
                goto skip_full_check;

        env->explored_states = kcalloc(env->prog->len,
                                       sizeof(struct bpf_verifier_state_list *),
                                       GFP_USER);
        ret = -ENOMEM;
        if (!env->explored_states)
                goto skip_full_check;

        ret = check_cfg(env);
        if (ret < 0)
                goto skip_full_check;

        env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);

        ret = do_check(env);
        if (env->cur_state) {
                free_verifier_state(env->cur_state, true);
                env->cur_state = NULL;
        }

skip_full_check:
        while (!pop_stack(env, NULL, NULL));
        free_states(env);

        if (ret == 0)
                sanitize_dead_code(env);

        if (ret == 0)
                /* program is valid, convert *(u32*)(ctx + off) accesses */
                ret = convert_ctx_accesses(env);

        if (ret == 0)
                ret = fixup_bpf_calls(env);

        if (log->level && bpf_verifier_log_full(log))
                ret = -ENOSPC;
        if (log->level && !log->ubuf) {
                ret = -EFAULT;
                goto err_release_maps;
        }

        if (ret == 0 && env->used_map_cnt) {
                /* if program passed verifier, update used_maps in bpf_prog_info */
                env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
                                                          sizeof(env->used_maps[0]),
                                                          GFP_KERNEL);

                if (!env->prog->aux->used_maps) {
                        ret = -ENOMEM;
                        goto err_release_maps;
                }

                memcpy(env->prog->aux->used_maps, env->used_maps,
                       sizeof(env->used_maps[0]) * env->used_map_cnt);
                env->prog->aux->used_map_cnt = env->used_map_cnt;

                /* program is valid. Convert pseudo bpf_ld_imm64 into generic
                 * bpf_ld_imm64 instructions
                 */
                convert_pseudo_ld_imm64(env);
        }

err_release_maps:
        if (!env->prog->aux->used_maps)
                /* if we didn't copy map pointers into bpf_prog_info, release
                 * them now. Otherwise free_bpf_prog_info() will release them.
                 */
                release_maps(env);
        *prog = env->prog;
err_unlock:
        mutex_unlock(&bpf_verifier_lock);
        vfree(env->insn_aux_data);
err_free_env:
        kfree(env);
        return ret;
}