]> git.proxmox.com Git - mirror_ubuntu-hirsute-kernel.git/blame - kernel/bpf/verifier.c
bpf: Add new bpf map type to store the pointer to struct perf_event
[mirror_ubuntu-hirsute-kernel.git] / kernel / bpf / verifier.c
CommitLineData
51580e79
AS
1/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * This program is distributed in the hope that it will be useful, but
8 * WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
10 * General Public License for more details.
11 */
12#include <linux/kernel.h>
13#include <linux/types.h>
14#include <linux/slab.h>
15#include <linux/bpf.h>
16#include <linux/filter.h>
17#include <net/netlink.h>
18#include <linux/file.h>
19#include <linux/vmalloc.h>
20
21/* bpf_check() is a static code analyzer that walks eBPF program
22 * instruction by instruction and updates register/stack state.
23 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
24 *
25 * The first pass is depth-first-search to check that the program is a DAG.
26 * It rejects the following programs:
27 * - larger than BPF_MAXINSNS insns
28 * - if loop is present (detected via back-edge)
29 * - unreachable insns exist (shouldn't be a forest. program = one function)
30 * - out of bounds or malformed jumps
31 * The second pass is all possible path descent from the 1st insn.
32 * Since it's analyzing all pathes through the program, the length of the
33 * analysis is limited to 32k insn, which may be hit even if total number of
34 * insn is less then 4K, but there are too many branches that change stack/regs.
35 * Number of 'branches to be analyzed' is limited to 1k
36 *
37 * On entry to each instruction, each register has a type, and the instruction
38 * changes the types of the registers depending on instruction semantics.
39 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
40 * copied to R1.
41 *
42 * All registers are 64-bit.
43 * R0 - return register
44 * R1-R5 argument passing registers
45 * R6-R9 callee saved registers
46 * R10 - frame pointer read-only
47 *
48 * At the start of BPF program the register R1 contains a pointer to bpf_context
49 * and has type PTR_TO_CTX.
50 *
51 * Verifier tracks arithmetic operations on pointers in case:
52 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
53 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
54 * 1st insn copies R10 (which has FRAME_PTR) type into R1
55 * and 2nd arithmetic instruction is pattern matched to recognize
56 * that it wants to construct a pointer to some element within stack.
57 * So after 2nd insn, the register R1 has type PTR_TO_STACK
58 * (and -20 constant is saved for further stack bounds checking).
59 * Meaning that this reg is a pointer to stack plus known immediate constant.
60 *
61 * Most of the time the registers have UNKNOWN_VALUE type, which
62 * means the register has some value, but it's not a valid pointer.
63 * (like pointer plus pointer becomes UNKNOWN_VALUE type)
64 *
65 * When verifier sees load or store instructions the type of base register
66 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
67 * types recognized by check_mem_access() function.
68 *
69 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
70 * and the range of [ptr, ptr + map's value_size) is accessible.
71 *
72 * registers used to pass values to function calls are checked against
73 * function argument constraints.
74 *
75 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
76 * It means that the register type passed to this function must be
77 * PTR_TO_STACK and it will be used inside the function as
78 * 'pointer to map element key'
79 *
80 * For example the argument constraints for bpf_map_lookup_elem():
81 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
82 * .arg1_type = ARG_CONST_MAP_PTR,
83 * .arg2_type = ARG_PTR_TO_MAP_KEY,
84 *
85 * ret_type says that this function returns 'pointer to map elem value or null'
86 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
87 * 2nd argument should be a pointer to stack, which will be used inside
88 * the helper function as a pointer to map element key.
89 *
90 * On the kernel side the helper function looks like:
91 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
92 * {
93 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
94 * void *key = (void *) (unsigned long) r2;
95 * void *value;
96 *
97 * here kernel can access 'key' and 'map' pointers safely, knowing that
98 * [key, key + map->key_size) bytes are valid and were initialized on
99 * the stack of eBPF program.
100 * }
101 *
102 * Corresponding eBPF program may look like:
103 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
104 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
105 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
106 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
107 * here verifier looks at prototype of map_lookup_elem() and sees:
108 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
109 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
110 *
111 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
112 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
113 * and were initialized prior to this call.
114 * If it's ok, then verifier allows this BPF_CALL insn and looks at
115 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
116 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
117 * returns ether pointer to map value or NULL.
118 *
119 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
120 * insn, the register holding that pointer in the true branch changes state to
121 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
122 * branch. See check_cond_jmp_op().
123 *
124 * After the call R0 is set to return type of the function and registers R1-R5
125 * are set to NOT_INIT to indicate that they are no longer readable.
126 */
127
17a52670
AS
128/* types of values stored in eBPF registers */
129enum bpf_reg_type {
130 NOT_INIT = 0, /* nothing was written into register */
131 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */
132 PTR_TO_CTX, /* reg points to bpf_context */
133 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */
134 PTR_TO_MAP_VALUE, /* reg points to map element value */
135 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
136 FRAME_PTR, /* reg == frame_pointer */
137 PTR_TO_STACK, /* reg == frame_pointer + imm */
138 CONST_IMM, /* constant integer value */
139};
140
141struct reg_state {
142 enum bpf_reg_type type;
143 union {
144 /* valid when type == CONST_IMM | PTR_TO_STACK */
145 int imm;
146
147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
148 * PTR_TO_MAP_VALUE_OR_NULL
149 */
150 struct bpf_map *map_ptr;
151 };
152};
153
154enum bpf_stack_slot_type {
155 STACK_INVALID, /* nothing was stored in this stack slot */
9c399760 156 STACK_SPILL, /* register spilled into stack */
17a52670
AS
157 STACK_MISC /* BPF program wrote some data into this slot */
158};
159
9c399760 160#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
17a52670
AS
161
162/* state of the program:
163 * type of all registers and stack info
164 */
165struct verifier_state {
166 struct reg_state regs[MAX_BPF_REG];
9c399760
AS
167 u8 stack_slot_type[MAX_BPF_STACK];
168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
17a52670
AS
169};
170
171/* linked list of verifier states used to prune search */
172struct verifier_state_list {
173 struct verifier_state state;
174 struct verifier_state_list *next;
175};
176
177/* verifier_state + insn_idx are pushed to stack when branch is encountered */
178struct verifier_stack_elem {
179 /* verifer state is 'st'
180 * before processing instruction 'insn_idx'
181 * and after processing instruction 'prev_insn_idx'
182 */
183 struct verifier_state st;
184 int insn_idx;
185 int prev_insn_idx;
186 struct verifier_stack_elem *next;
187};
188
0246e64d
AS
189#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
190
cbd35700
AS
191/* single container for all structs
192 * one verifier_env per bpf_check() call
193 */
194struct verifier_env {
0246e64d 195 struct bpf_prog *prog; /* eBPF program being verified */
17a52670
AS
196 struct verifier_stack_elem *head; /* stack of verifier states to be processed */
197 int stack_size; /* number of states to be processed */
198 struct verifier_state cur_state; /* current verifier state */
f1bca824 199 struct verifier_state_list **explored_states; /* search pruning optimization */
0246e64d
AS
200 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
201 u32 used_map_cnt; /* number of used maps */
cbd35700
AS
202};
203
204/* verbose verifier prints what it's seeing
205 * bpf_check() is called under lock, so no race to access these global vars
206 */
207static u32 log_level, log_size, log_len;
208static char *log_buf;
209
210static DEFINE_MUTEX(bpf_verifier_lock);
211
212/* log_level controls verbosity level of eBPF verifier.
213 * verbose() is used to dump the verification trace to the log, so the user
214 * can figure out what's wrong with the program
215 */
216static void verbose(const char *fmt, ...)
217{
218 va_list args;
219
220 if (log_level == 0 || log_len >= log_size - 1)
221 return;
222
223 va_start(args, fmt);
224 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
225 va_end(args);
226}
227
17a52670
AS
228/* string representation of 'enum bpf_reg_type' */
229static const char * const reg_type_str[] = {
230 [NOT_INIT] = "?",
231 [UNKNOWN_VALUE] = "inv",
232 [PTR_TO_CTX] = "ctx",
233 [CONST_PTR_TO_MAP] = "map_ptr",
234 [PTR_TO_MAP_VALUE] = "map_value",
235 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
236 [FRAME_PTR] = "fp",
237 [PTR_TO_STACK] = "fp",
238 [CONST_IMM] = "imm",
239};
240
241static void print_verifier_state(struct verifier_env *env)
242{
243 enum bpf_reg_type t;
244 int i;
245
246 for (i = 0; i < MAX_BPF_REG; i++) {
247 t = env->cur_state.regs[i].type;
248 if (t == NOT_INIT)
249 continue;
250 verbose(" R%d=%s", i, reg_type_str[t]);
251 if (t == CONST_IMM || t == PTR_TO_STACK)
252 verbose("%d", env->cur_state.regs[i].imm);
253 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
254 t == PTR_TO_MAP_VALUE_OR_NULL)
255 verbose("(ks=%d,vs=%d)",
256 env->cur_state.regs[i].map_ptr->key_size,
257 env->cur_state.regs[i].map_ptr->value_size);
258 }
9c399760
AS
259 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
260 if (env->cur_state.stack_slot_type[i] == STACK_SPILL)
17a52670 261 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
9c399760 262 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]);
17a52670
AS
263 }
264 verbose("\n");
265}
266
cbd35700
AS
267static const char *const bpf_class_string[] = {
268 [BPF_LD] = "ld",
269 [BPF_LDX] = "ldx",
270 [BPF_ST] = "st",
271 [BPF_STX] = "stx",
272 [BPF_ALU] = "alu",
273 [BPF_JMP] = "jmp",
274 [BPF_RET] = "BUG",
275 [BPF_ALU64] = "alu64",
276};
277
278static const char *const bpf_alu_string[] = {
279 [BPF_ADD >> 4] = "+=",
280 [BPF_SUB >> 4] = "-=",
281 [BPF_MUL >> 4] = "*=",
282 [BPF_DIV >> 4] = "/=",
283 [BPF_OR >> 4] = "|=",
284 [BPF_AND >> 4] = "&=",
285 [BPF_LSH >> 4] = "<<=",
286 [BPF_RSH >> 4] = ">>=",
287 [BPF_NEG >> 4] = "neg",
288 [BPF_MOD >> 4] = "%=",
289 [BPF_XOR >> 4] = "^=",
290 [BPF_MOV >> 4] = "=",
291 [BPF_ARSH >> 4] = "s>>=",
292 [BPF_END >> 4] = "endian",
293};
294
295static const char *const bpf_ldst_string[] = {
296 [BPF_W >> 3] = "u32",
297 [BPF_H >> 3] = "u16",
298 [BPF_B >> 3] = "u8",
299 [BPF_DW >> 3] = "u64",
300};
301
302static const char *const bpf_jmp_string[] = {
303 [BPF_JA >> 4] = "jmp",
304 [BPF_JEQ >> 4] = "==",
305 [BPF_JGT >> 4] = ">",
306 [BPF_JGE >> 4] = ">=",
307 [BPF_JSET >> 4] = "&",
308 [BPF_JNE >> 4] = "!=",
309 [BPF_JSGT >> 4] = "s>",
310 [BPF_JSGE >> 4] = "s>=",
311 [BPF_CALL >> 4] = "call",
312 [BPF_EXIT >> 4] = "exit",
313};
314
315static void print_bpf_insn(struct bpf_insn *insn)
316{
317 u8 class = BPF_CLASS(insn->code);
318
319 if (class == BPF_ALU || class == BPF_ALU64) {
320 if (BPF_SRC(insn->code) == BPF_X)
321 verbose("(%02x) %sr%d %s %sr%d\n",
322 insn->code, class == BPF_ALU ? "(u32) " : "",
323 insn->dst_reg,
324 bpf_alu_string[BPF_OP(insn->code) >> 4],
325 class == BPF_ALU ? "(u32) " : "",
326 insn->src_reg);
327 else
328 verbose("(%02x) %sr%d %s %s%d\n",
329 insn->code, class == BPF_ALU ? "(u32) " : "",
330 insn->dst_reg,
331 bpf_alu_string[BPF_OP(insn->code) >> 4],
332 class == BPF_ALU ? "(u32) " : "",
333 insn->imm);
334 } else if (class == BPF_STX) {
335 if (BPF_MODE(insn->code) == BPF_MEM)
336 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
337 insn->code,
338 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
339 insn->dst_reg,
340 insn->off, insn->src_reg);
341 else if (BPF_MODE(insn->code) == BPF_XADD)
342 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
343 insn->code,
344 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
345 insn->dst_reg, insn->off,
346 insn->src_reg);
347 else
348 verbose("BUG_%02x\n", insn->code);
349 } else if (class == BPF_ST) {
350 if (BPF_MODE(insn->code) != BPF_MEM) {
351 verbose("BUG_st_%02x\n", insn->code);
352 return;
353 }
354 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
355 insn->code,
356 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
357 insn->dst_reg,
358 insn->off, insn->imm);
359 } else if (class == BPF_LDX) {
360 if (BPF_MODE(insn->code) != BPF_MEM) {
361 verbose("BUG_ldx_%02x\n", insn->code);
362 return;
363 }
364 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
365 insn->code, insn->dst_reg,
366 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
367 insn->src_reg, insn->off);
368 } else if (class == BPF_LD) {
369 if (BPF_MODE(insn->code) == BPF_ABS) {
370 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
371 insn->code,
372 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
373 insn->imm);
374 } else if (BPF_MODE(insn->code) == BPF_IND) {
375 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
376 insn->code,
377 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
378 insn->src_reg, insn->imm);
379 } else if (BPF_MODE(insn->code) == BPF_IMM) {
380 verbose("(%02x) r%d = 0x%x\n",
381 insn->code, insn->dst_reg, insn->imm);
382 } else {
383 verbose("BUG_ld_%02x\n", insn->code);
384 return;
385 }
386 } else if (class == BPF_JMP) {
387 u8 opcode = BPF_OP(insn->code);
388
389 if (opcode == BPF_CALL) {
390 verbose("(%02x) call %d\n", insn->code, insn->imm);
391 } else if (insn->code == (BPF_JMP | BPF_JA)) {
392 verbose("(%02x) goto pc%+d\n",
393 insn->code, insn->off);
394 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
395 verbose("(%02x) exit\n", insn->code);
396 } else if (BPF_SRC(insn->code) == BPF_X) {
397 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
398 insn->code, insn->dst_reg,
399 bpf_jmp_string[BPF_OP(insn->code) >> 4],
400 insn->src_reg, insn->off);
401 } else {
402 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
403 insn->code, insn->dst_reg,
404 bpf_jmp_string[BPF_OP(insn->code) >> 4],
405 insn->imm, insn->off);
406 }
407 } else {
408 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
409 }
410}
411
17a52670
AS
412static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
413{
414 struct verifier_stack_elem *elem;
415 int insn_idx;
416
417 if (env->head == NULL)
418 return -1;
419
420 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
421 insn_idx = env->head->insn_idx;
422 if (prev_insn_idx)
423 *prev_insn_idx = env->head->prev_insn_idx;
424 elem = env->head->next;
425 kfree(env->head);
426 env->head = elem;
427 env->stack_size--;
428 return insn_idx;
429}
430
431static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
432 int prev_insn_idx)
433{
434 struct verifier_stack_elem *elem;
435
436 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
437 if (!elem)
438 goto err;
439
440 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
441 elem->insn_idx = insn_idx;
442 elem->prev_insn_idx = prev_insn_idx;
443 elem->next = env->head;
444 env->head = elem;
445 env->stack_size++;
446 if (env->stack_size > 1024) {
447 verbose("BPF program is too complex\n");
448 goto err;
449 }
450 return &elem->st;
451err:
452 /* pop all elements and return */
453 while (pop_stack(env, NULL) >= 0);
454 return NULL;
455}
456
457#define CALLER_SAVED_REGS 6
458static const int caller_saved[CALLER_SAVED_REGS] = {
459 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
460};
461
462static void init_reg_state(struct reg_state *regs)
463{
464 int i;
465
466 for (i = 0; i < MAX_BPF_REG; i++) {
467 regs[i].type = NOT_INIT;
468 regs[i].imm = 0;
469 regs[i].map_ptr = NULL;
470 }
471
472 /* frame pointer */
473 regs[BPF_REG_FP].type = FRAME_PTR;
474
475 /* 1st arg to a function */
476 regs[BPF_REG_1].type = PTR_TO_CTX;
477}
478
479static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
480{
481 BUG_ON(regno >= MAX_BPF_REG);
482 regs[regno].type = UNKNOWN_VALUE;
483 regs[regno].imm = 0;
484 regs[regno].map_ptr = NULL;
485}
486
487enum reg_arg_type {
488 SRC_OP, /* register is used as source operand */
489 DST_OP, /* register is used as destination operand */
490 DST_OP_NO_MARK /* same as above, check only, don't mark */
491};
492
493static int check_reg_arg(struct reg_state *regs, u32 regno,
494 enum reg_arg_type t)
495{
496 if (regno >= MAX_BPF_REG) {
497 verbose("R%d is invalid\n", regno);
498 return -EINVAL;
499 }
500
501 if (t == SRC_OP) {
502 /* check whether register used as source operand can be read */
503 if (regs[regno].type == NOT_INIT) {
504 verbose("R%d !read_ok\n", regno);
505 return -EACCES;
506 }
507 } else {
508 /* check whether register used as dest operand can be written to */
509 if (regno == BPF_REG_FP) {
510 verbose("frame pointer is read only\n");
511 return -EACCES;
512 }
513 if (t == DST_OP)
514 mark_reg_unknown_value(regs, regno);
515 }
516 return 0;
517}
518
519static int bpf_size_to_bytes(int bpf_size)
520{
521 if (bpf_size == BPF_W)
522 return 4;
523 else if (bpf_size == BPF_H)
524 return 2;
525 else if (bpf_size == BPF_B)
526 return 1;
527 else if (bpf_size == BPF_DW)
528 return 8;
529 else
530 return -EINVAL;
531}
532
533/* check_stack_read/write functions track spill/fill of registers,
534 * stack boundary and alignment are checked in check_mem_access()
535 */
536static int check_stack_write(struct verifier_state *state, int off, int size,
537 int value_regno)
538{
17a52670 539 int i;
9c399760
AS
540 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
541 * so it's aligned access and [off, off + size) are within stack limits
542 */
17a52670
AS
543
544 if (value_regno >= 0 &&
545 (state->regs[value_regno].type == PTR_TO_MAP_VALUE ||
546 state->regs[value_regno].type == PTR_TO_STACK ||
547 state->regs[value_regno].type == PTR_TO_CTX)) {
548
549 /* register containing pointer is being spilled into stack */
9c399760 550 if (size != BPF_REG_SIZE) {
17a52670
AS
551 verbose("invalid size of register spill\n");
552 return -EACCES;
553 }
554
17a52670 555 /* save register state */
9c399760
AS
556 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
557 state->regs[value_regno];
17a52670 558
9c399760
AS
559 for (i = 0; i < BPF_REG_SIZE; i++)
560 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
561 } else {
17a52670 562 /* regular write of data into stack */
9c399760
AS
563 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
564 (struct reg_state) {};
565
566 for (i = 0; i < size; i++)
567 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
17a52670
AS
568 }
569 return 0;
570}
571
572static int check_stack_read(struct verifier_state *state, int off, int size,
573 int value_regno)
574{
9c399760 575 u8 *slot_type;
17a52670 576 int i;
17a52670 577
9c399760 578 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
17a52670 579
9c399760
AS
580 if (slot_type[0] == STACK_SPILL) {
581 if (size != BPF_REG_SIZE) {
17a52670
AS
582 verbose("invalid size of register spill\n");
583 return -EACCES;
584 }
9c399760
AS
585 for (i = 1; i < BPF_REG_SIZE; i++) {
586 if (slot_type[i] != STACK_SPILL) {
17a52670
AS
587 verbose("corrupted spill memory\n");
588 return -EACCES;
589 }
590 }
591
592 if (value_regno >= 0)
593 /* restore register state from stack */
9c399760
AS
594 state->regs[value_regno] =
595 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
17a52670
AS
596 return 0;
597 } else {
598 for (i = 0; i < size; i++) {
9c399760 599 if (slot_type[i] != STACK_MISC) {
17a52670
AS
600 verbose("invalid read from stack off %d+%d size %d\n",
601 off, i, size);
602 return -EACCES;
603 }
604 }
605 if (value_regno >= 0)
606 /* have read misc data from the stack */
607 mark_reg_unknown_value(state->regs, value_regno);
608 return 0;
609 }
610}
611
612/* check read/write into map element returned by bpf_map_lookup_elem() */
613static int check_map_access(struct verifier_env *env, u32 regno, int off,
614 int size)
615{
616 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
617
618 if (off < 0 || off + size > map->value_size) {
619 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
620 map->value_size, off, size);
621 return -EACCES;
622 }
623 return 0;
624}
625
626/* check access to 'struct bpf_context' fields */
627static int check_ctx_access(struct verifier_env *env, int off, int size,
628 enum bpf_access_type t)
629{
630 if (env->prog->aux->ops->is_valid_access &&
631 env->prog->aux->ops->is_valid_access(off, size, t))
632 return 0;
633
634 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
635 return -EACCES;
636}
637
638/* check whether memory at (regno + off) is accessible for t = (read | write)
639 * if t==write, value_regno is a register which value is stored into memory
640 * if t==read, value_regno is a register which will receive the value from memory
641 * if t==write && value_regno==-1, some unknown value is stored into memory
642 * if t==read && value_regno==-1, don't care what we read from memory
643 */
644static int check_mem_access(struct verifier_env *env, u32 regno, int off,
645 int bpf_size, enum bpf_access_type t,
646 int value_regno)
647{
648 struct verifier_state *state = &env->cur_state;
649 int size, err = 0;
650
24b4d2ab
AG
651 if (state->regs[regno].type == PTR_TO_STACK)
652 off += state->regs[regno].imm;
653
17a52670
AS
654 size = bpf_size_to_bytes(bpf_size);
655 if (size < 0)
656 return size;
657
658 if (off % size != 0) {
659 verbose("misaligned access off %d size %d\n", off, size);
660 return -EACCES;
661 }
662
663 if (state->regs[regno].type == PTR_TO_MAP_VALUE) {
664 err = check_map_access(env, regno, off, size);
665 if (!err && t == BPF_READ && value_regno >= 0)
666 mark_reg_unknown_value(state->regs, value_regno);
667
668 } else if (state->regs[regno].type == PTR_TO_CTX) {
669 err = check_ctx_access(env, off, size, t);
670 if (!err && t == BPF_READ && value_regno >= 0)
671 mark_reg_unknown_value(state->regs, value_regno);
672
24b4d2ab
AG
673 } else if (state->regs[regno].type == FRAME_PTR ||
674 state->regs[regno].type == PTR_TO_STACK) {
17a52670
AS
675 if (off >= 0 || off < -MAX_BPF_STACK) {
676 verbose("invalid stack off=%d size=%d\n", off, size);
677 return -EACCES;
678 }
679 if (t == BPF_WRITE)
680 err = check_stack_write(state, off, size, value_regno);
681 else
682 err = check_stack_read(state, off, size, value_regno);
683 } else {
684 verbose("R%d invalid mem access '%s'\n",
685 regno, reg_type_str[state->regs[regno].type]);
686 return -EACCES;
687 }
688 return err;
689}
690
691static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
692{
693 struct reg_state *regs = env->cur_state.regs;
694 int err;
695
696 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
697 insn->imm != 0) {
698 verbose("BPF_XADD uses reserved fields\n");
699 return -EINVAL;
700 }
701
702 /* check src1 operand */
703 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
704 if (err)
705 return err;
706
707 /* check src2 operand */
708 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
709 if (err)
710 return err;
711
712 /* check whether atomic_add can read the memory */
713 err = check_mem_access(env, insn->dst_reg, insn->off,
714 BPF_SIZE(insn->code), BPF_READ, -1);
715 if (err)
716 return err;
717
718 /* check whether atomic_add can write into the same memory */
719 return check_mem_access(env, insn->dst_reg, insn->off,
720 BPF_SIZE(insn->code), BPF_WRITE, -1);
721}
722
723/* when register 'regno' is passed into function that will read 'access_size'
724 * bytes from that pointer, make sure that it's within stack boundary
725 * and all elements of stack are initialized
726 */
727static int check_stack_boundary(struct verifier_env *env,
728 int regno, int access_size)
729{
730 struct verifier_state *state = &env->cur_state;
731 struct reg_state *regs = state->regs;
732 int off, i;
733
734 if (regs[regno].type != PTR_TO_STACK)
735 return -EACCES;
736
737 off = regs[regno].imm;
738 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
739 access_size <= 0) {
740 verbose("invalid stack type R%d off=%d access_size=%d\n",
741 regno, off, access_size);
742 return -EACCES;
743 }
744
745 for (i = 0; i < access_size; i++) {
9c399760 746 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
17a52670
AS
747 verbose("invalid indirect read from stack off %d+%d size %d\n",
748 off, i, access_size);
749 return -EACCES;
750 }
751 }
752 return 0;
753}
754
755static int check_func_arg(struct verifier_env *env, u32 regno,
756 enum bpf_arg_type arg_type, struct bpf_map **mapp)
757{
758 struct reg_state *reg = env->cur_state.regs + regno;
759 enum bpf_reg_type expected_type;
760 int err = 0;
761
80f1d68c 762 if (arg_type == ARG_DONTCARE)
17a52670
AS
763 return 0;
764
765 if (reg->type == NOT_INIT) {
766 verbose("R%d !read_ok\n", regno);
767 return -EACCES;
768 }
769
80f1d68c
DB
770 if (arg_type == ARG_ANYTHING)
771 return 0;
772
17a52670
AS
773 if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
774 arg_type == ARG_PTR_TO_MAP_VALUE) {
775 expected_type = PTR_TO_STACK;
776 } else if (arg_type == ARG_CONST_STACK_SIZE) {
777 expected_type = CONST_IMM;
778 } else if (arg_type == ARG_CONST_MAP_PTR) {
779 expected_type = CONST_PTR_TO_MAP;
608cd71a
AS
780 } else if (arg_type == ARG_PTR_TO_CTX) {
781 expected_type = PTR_TO_CTX;
17a52670
AS
782 } else {
783 verbose("unsupported arg_type %d\n", arg_type);
784 return -EFAULT;
785 }
786
787 if (reg->type != expected_type) {
788 verbose("R%d type=%s expected=%s\n", regno,
789 reg_type_str[reg->type], reg_type_str[expected_type]);
790 return -EACCES;
791 }
792
793 if (arg_type == ARG_CONST_MAP_PTR) {
794 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
795 *mapp = reg->map_ptr;
796
797 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
798 /* bpf_map_xxx(..., map_ptr, ..., key) call:
799 * check that [key, key + map->key_size) are within
800 * stack limits and initialized
801 */
802 if (!*mapp) {
803 /* in function declaration map_ptr must come before
804 * map_key, so that it's verified and known before
805 * we have to check map_key here. Otherwise it means
806 * that kernel subsystem misconfigured verifier
807 */
808 verbose("invalid map_ptr to access map->key\n");
809 return -EACCES;
810 }
811 err = check_stack_boundary(env, regno, (*mapp)->key_size);
812
813 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
814 /* bpf_map_xxx(..., map_ptr, ..., value) call:
815 * check [value, value + map->value_size) validity
816 */
817 if (!*mapp) {
818 /* kernel subsystem misconfigured verifier */
819 verbose("invalid map_ptr to access map->value\n");
820 return -EACCES;
821 }
822 err = check_stack_boundary(env, regno, (*mapp)->value_size);
823
824 } else if (arg_type == ARG_CONST_STACK_SIZE) {
825 /* bpf_xxx(..., buf, len) call will access 'len' bytes
826 * from stack pointer 'buf'. Check it
827 * note: regno == len, regno - 1 == buf
828 */
829 if (regno == 0) {
830 /* kernel subsystem misconfigured verifier */
831 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
832 return -EACCES;
833 }
834 err = check_stack_boundary(env, regno - 1, reg->imm);
835 }
836
837 return err;
838}
839
840static int check_call(struct verifier_env *env, int func_id)
841{
842 struct verifier_state *state = &env->cur_state;
843 const struct bpf_func_proto *fn = NULL;
844 struct reg_state *regs = state->regs;
845 struct bpf_map *map = NULL;
846 struct reg_state *reg;
847 int i, err;
848
849 /* find function prototype */
850 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
851 verbose("invalid func %d\n", func_id);
852 return -EINVAL;
853 }
854
855 if (env->prog->aux->ops->get_func_proto)
856 fn = env->prog->aux->ops->get_func_proto(func_id);
857
858 if (!fn) {
859 verbose("unknown func %d\n", func_id);
860 return -EINVAL;
861 }
862
863 /* eBPF programs must be GPL compatible to use GPL-ed functions */
24701ece 864 if (!env->prog->gpl_compatible && fn->gpl_only) {
17a52670
AS
865 verbose("cannot call GPL only function from proprietary program\n");
866 return -EINVAL;
867 }
868
869 /* check args */
870 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map);
871 if (err)
872 return err;
873 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map);
874 if (err)
875 return err;
876 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map);
877 if (err)
878 return err;
879 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map);
880 if (err)
881 return err;
882 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map);
883 if (err)
884 return err;
885
886 /* reset caller saved regs */
887 for (i = 0; i < CALLER_SAVED_REGS; i++) {
888 reg = regs + caller_saved[i];
889 reg->type = NOT_INIT;
890 reg->imm = 0;
891 }
892
893 /* update return register */
894 if (fn->ret_type == RET_INTEGER) {
895 regs[BPF_REG_0].type = UNKNOWN_VALUE;
896 } else if (fn->ret_type == RET_VOID) {
897 regs[BPF_REG_0].type = NOT_INIT;
898 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
899 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
900 /* remember map_ptr, so that check_map_access()
901 * can check 'value_size' boundary of memory access
902 * to map element returned from bpf_map_lookup_elem()
903 */
904 if (map == NULL) {
905 verbose("kernel subsystem misconfigured verifier\n");
906 return -EINVAL;
907 }
908 regs[BPF_REG_0].map_ptr = map;
909 } else {
910 verbose("unknown return type %d of func %d\n",
911 fn->ret_type, func_id);
912 return -EINVAL;
913 }
04fd61ab
AS
914
915 if (map && map->map_type == BPF_MAP_TYPE_PROG_ARRAY &&
916 func_id != BPF_FUNC_tail_call)
917 /* prog_array map type needs extra care:
918 * only allow to pass it into bpf_tail_call() for now.
919 * bpf_map_delete_elem() can be allowed in the future,
920 * while bpf_map_update_elem() must only be done via syscall
921 */
922 return -EINVAL;
923
924 if (func_id == BPF_FUNC_tail_call &&
925 map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
926 /* don't allow any other map type to be passed into
927 * bpf_tail_call()
928 */
929 return -EINVAL;
930
17a52670
AS
931 return 0;
932}
933
934/* check validity of 32-bit and 64-bit arithmetic operations */
935static int check_alu_op(struct reg_state *regs, struct bpf_insn *insn)
936{
937 u8 opcode = BPF_OP(insn->code);
938 int err;
939
940 if (opcode == BPF_END || opcode == BPF_NEG) {
941 if (opcode == BPF_NEG) {
942 if (BPF_SRC(insn->code) != 0 ||
943 insn->src_reg != BPF_REG_0 ||
944 insn->off != 0 || insn->imm != 0) {
945 verbose("BPF_NEG uses reserved fields\n");
946 return -EINVAL;
947 }
948 } else {
949 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
950 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
951 verbose("BPF_END uses reserved fields\n");
952 return -EINVAL;
953 }
954 }
955
956 /* check src operand */
957 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
958 if (err)
959 return err;
960
961 /* check dest operand */
962 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
963 if (err)
964 return err;
965
966 } else if (opcode == BPF_MOV) {
967
968 if (BPF_SRC(insn->code) == BPF_X) {
969 if (insn->imm != 0 || insn->off != 0) {
970 verbose("BPF_MOV uses reserved fields\n");
971 return -EINVAL;
972 }
973
974 /* check src operand */
975 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
976 if (err)
977 return err;
978 } else {
979 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
980 verbose("BPF_MOV uses reserved fields\n");
981 return -EINVAL;
982 }
983 }
984
985 /* check dest operand */
986 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
987 if (err)
988 return err;
989
990 if (BPF_SRC(insn->code) == BPF_X) {
991 if (BPF_CLASS(insn->code) == BPF_ALU64) {
992 /* case: R1 = R2
993 * copy register state to dest reg
994 */
995 regs[insn->dst_reg] = regs[insn->src_reg];
996 } else {
997 regs[insn->dst_reg].type = UNKNOWN_VALUE;
998 regs[insn->dst_reg].map_ptr = NULL;
999 }
1000 } else {
1001 /* case: R = imm
1002 * remember the value we stored into this reg
1003 */
1004 regs[insn->dst_reg].type = CONST_IMM;
1005 regs[insn->dst_reg].imm = insn->imm;
1006 }
1007
1008 } else if (opcode > BPF_END) {
1009 verbose("invalid BPF_ALU opcode %x\n", opcode);
1010 return -EINVAL;
1011
1012 } else { /* all other ALU ops: and, sub, xor, add, ... */
1013
1014 bool stack_relative = false;
1015
1016 if (BPF_SRC(insn->code) == BPF_X) {
1017 if (insn->imm != 0 || insn->off != 0) {
1018 verbose("BPF_ALU uses reserved fields\n");
1019 return -EINVAL;
1020 }
1021 /* check src1 operand */
1022 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1023 if (err)
1024 return err;
1025 } else {
1026 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1027 verbose("BPF_ALU uses reserved fields\n");
1028 return -EINVAL;
1029 }
1030 }
1031
1032 /* check src2 operand */
1033 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1034 if (err)
1035 return err;
1036
1037 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1038 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1039 verbose("div by zero\n");
1040 return -EINVAL;
1041 }
1042
1043 /* pattern match 'bpf_add Rx, imm' instruction */
1044 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1045 regs[insn->dst_reg].type == FRAME_PTR &&
1046 BPF_SRC(insn->code) == BPF_K)
1047 stack_relative = true;
1048
1049 /* check dest operand */
1050 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1051 if (err)
1052 return err;
1053
1054 if (stack_relative) {
1055 regs[insn->dst_reg].type = PTR_TO_STACK;
1056 regs[insn->dst_reg].imm = insn->imm;
1057 }
1058 }
1059
1060 return 0;
1061}
1062
1063static int check_cond_jmp_op(struct verifier_env *env,
1064 struct bpf_insn *insn, int *insn_idx)
1065{
1066 struct reg_state *regs = env->cur_state.regs;
1067 struct verifier_state *other_branch;
1068 u8 opcode = BPF_OP(insn->code);
1069 int err;
1070
1071 if (opcode > BPF_EXIT) {
1072 verbose("invalid BPF_JMP opcode %x\n", opcode);
1073 return -EINVAL;
1074 }
1075
1076 if (BPF_SRC(insn->code) == BPF_X) {
1077 if (insn->imm != 0) {
1078 verbose("BPF_JMP uses reserved fields\n");
1079 return -EINVAL;
1080 }
1081
1082 /* check src1 operand */
1083 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1084 if (err)
1085 return err;
1086 } else {
1087 if (insn->src_reg != BPF_REG_0) {
1088 verbose("BPF_JMP uses reserved fields\n");
1089 return -EINVAL;
1090 }
1091 }
1092
1093 /* check src2 operand */
1094 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1095 if (err)
1096 return err;
1097
1098 /* detect if R == 0 where R was initialized to zero earlier */
1099 if (BPF_SRC(insn->code) == BPF_K &&
1100 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1101 regs[insn->dst_reg].type == CONST_IMM &&
1102 regs[insn->dst_reg].imm == insn->imm) {
1103 if (opcode == BPF_JEQ) {
1104 /* if (imm == imm) goto pc+off;
1105 * only follow the goto, ignore fall-through
1106 */
1107 *insn_idx += insn->off;
1108 return 0;
1109 } else {
1110 /* if (imm != imm) goto pc+off;
1111 * only follow fall-through branch, since
1112 * that's where the program will go
1113 */
1114 return 0;
1115 }
1116 }
1117
1118 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1119 if (!other_branch)
1120 return -EFAULT;
1121
1122 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1123 if (BPF_SRC(insn->code) == BPF_K &&
1124 insn->imm == 0 && (opcode == BPF_JEQ ||
1125 opcode == BPF_JNE) &&
1126 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1127 if (opcode == BPF_JEQ) {
1128 /* next fallthrough insn can access memory via
1129 * this register
1130 */
1131 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1132 /* branch targer cannot access it, since reg == 0 */
1133 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1134 other_branch->regs[insn->dst_reg].imm = 0;
1135 } else {
1136 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1137 regs[insn->dst_reg].type = CONST_IMM;
1138 regs[insn->dst_reg].imm = 0;
1139 }
1140 } else if (BPF_SRC(insn->code) == BPF_K &&
1141 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1142
1143 if (opcode == BPF_JEQ) {
1144 /* detect if (R == imm) goto
1145 * and in the target state recognize that R = imm
1146 */
1147 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1148 other_branch->regs[insn->dst_reg].imm = insn->imm;
1149 } else {
1150 /* detect if (R != imm) goto
1151 * and in the fall-through state recognize that R = imm
1152 */
1153 regs[insn->dst_reg].type = CONST_IMM;
1154 regs[insn->dst_reg].imm = insn->imm;
1155 }
1156 }
1157 if (log_level)
1158 print_verifier_state(env);
1159 return 0;
1160}
1161
0246e64d
AS
1162/* return the map pointer stored inside BPF_LD_IMM64 instruction */
1163static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1164{
1165 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1166
1167 return (struct bpf_map *) (unsigned long) imm64;
1168}
1169
17a52670
AS
1170/* verify BPF_LD_IMM64 instruction */
1171static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1172{
1173 struct reg_state *regs = env->cur_state.regs;
1174 int err;
1175
1176 if (BPF_SIZE(insn->code) != BPF_DW) {
1177 verbose("invalid BPF_LD_IMM insn\n");
1178 return -EINVAL;
1179 }
1180 if (insn->off != 0) {
1181 verbose("BPF_LD_IMM64 uses reserved fields\n");
1182 return -EINVAL;
1183 }
1184
1185 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1186 if (err)
1187 return err;
1188
1189 if (insn->src_reg == 0)
1190 /* generic move 64-bit immediate into a register */
1191 return 0;
1192
1193 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1194 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1195
1196 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1197 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1198 return 0;
1199}
1200
96be4325
DB
1201static bool may_access_skb(enum bpf_prog_type type)
1202{
1203 switch (type) {
1204 case BPF_PROG_TYPE_SOCKET_FILTER:
1205 case BPF_PROG_TYPE_SCHED_CLS:
94caee8c 1206 case BPF_PROG_TYPE_SCHED_ACT:
96be4325
DB
1207 return true;
1208 default:
1209 return false;
1210 }
1211}
1212
ddd872bc
AS
1213/* verify safety of LD_ABS|LD_IND instructions:
1214 * - they can only appear in the programs where ctx == skb
1215 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1216 * preserve R6-R9, and store return value into R0
1217 *
1218 * Implicit input:
1219 * ctx == skb == R6 == CTX
1220 *
1221 * Explicit input:
1222 * SRC == any register
1223 * IMM == 32-bit immediate
1224 *
1225 * Output:
1226 * R0 - 8/16/32-bit skb data converted to cpu endianness
1227 */
1228static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1229{
1230 struct reg_state *regs = env->cur_state.regs;
1231 u8 mode = BPF_MODE(insn->code);
1232 struct reg_state *reg;
1233 int i, err;
1234
24701ece 1235 if (!may_access_skb(env->prog->type)) {
96be4325 1236 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n");
ddd872bc
AS
1237 return -EINVAL;
1238 }
1239
1240 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1241 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1242 verbose("BPF_LD_ABS uses reserved fields\n");
1243 return -EINVAL;
1244 }
1245
1246 /* check whether implicit source operand (register R6) is readable */
1247 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1248 if (err)
1249 return err;
1250
1251 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1252 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1253 return -EINVAL;
1254 }
1255
1256 if (mode == BPF_IND) {
1257 /* check explicit source operand */
1258 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1259 if (err)
1260 return err;
1261 }
1262
1263 /* reset caller saved regs to unreadable */
1264 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1265 reg = regs + caller_saved[i];
1266 reg->type = NOT_INIT;
1267 reg->imm = 0;
1268 }
1269
1270 /* mark destination R0 register as readable, since it contains
1271 * the value fetched from the packet
1272 */
1273 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1274 return 0;
1275}
1276
475fb78f
AS
1277/* non-recursive DFS pseudo code
1278 * 1 procedure DFS-iterative(G,v):
1279 * 2 label v as discovered
1280 * 3 let S be a stack
1281 * 4 S.push(v)
1282 * 5 while S is not empty
1283 * 6 t <- S.pop()
1284 * 7 if t is what we're looking for:
1285 * 8 return t
1286 * 9 for all edges e in G.adjacentEdges(t) do
1287 * 10 if edge e is already labelled
1288 * 11 continue with the next edge
1289 * 12 w <- G.adjacentVertex(t,e)
1290 * 13 if vertex w is not discovered and not explored
1291 * 14 label e as tree-edge
1292 * 15 label w as discovered
1293 * 16 S.push(w)
1294 * 17 continue at 5
1295 * 18 else if vertex w is discovered
1296 * 19 label e as back-edge
1297 * 20 else
1298 * 21 // vertex w is explored
1299 * 22 label e as forward- or cross-edge
1300 * 23 label t as explored
1301 * 24 S.pop()
1302 *
1303 * convention:
1304 * 0x10 - discovered
1305 * 0x11 - discovered and fall-through edge labelled
1306 * 0x12 - discovered and fall-through and branch edges labelled
1307 * 0x20 - explored
1308 */
1309
1310enum {
1311 DISCOVERED = 0x10,
1312 EXPLORED = 0x20,
1313 FALLTHROUGH = 1,
1314 BRANCH = 2,
1315};
1316
f1bca824
AS
1317#define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1318
475fb78f
AS
1319static int *insn_stack; /* stack of insns to process */
1320static int cur_stack; /* current stack index */
1321static int *insn_state;
1322
1323/* t, w, e - match pseudo-code above:
1324 * t - index of current instruction
1325 * w - next instruction
1326 * e - edge
1327 */
1328static int push_insn(int t, int w, int e, struct verifier_env *env)
1329{
1330 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1331 return 0;
1332
1333 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1334 return 0;
1335
1336 if (w < 0 || w >= env->prog->len) {
1337 verbose("jump out of range from insn %d to %d\n", t, w);
1338 return -EINVAL;
1339 }
1340
f1bca824
AS
1341 if (e == BRANCH)
1342 /* mark branch target for state pruning */
1343 env->explored_states[w] = STATE_LIST_MARK;
1344
475fb78f
AS
1345 if (insn_state[w] == 0) {
1346 /* tree-edge */
1347 insn_state[t] = DISCOVERED | e;
1348 insn_state[w] = DISCOVERED;
1349 if (cur_stack >= env->prog->len)
1350 return -E2BIG;
1351 insn_stack[cur_stack++] = w;
1352 return 1;
1353 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1354 verbose("back-edge from insn %d to %d\n", t, w);
1355 return -EINVAL;
1356 } else if (insn_state[w] == EXPLORED) {
1357 /* forward- or cross-edge */
1358 insn_state[t] = DISCOVERED | e;
1359 } else {
1360 verbose("insn state internal bug\n");
1361 return -EFAULT;
1362 }
1363 return 0;
1364}
1365
1366/* non-recursive depth-first-search to detect loops in BPF program
1367 * loop == back-edge in directed graph
1368 */
1369static int check_cfg(struct verifier_env *env)
1370{
1371 struct bpf_insn *insns = env->prog->insnsi;
1372 int insn_cnt = env->prog->len;
1373 int ret = 0;
1374 int i, t;
1375
1376 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1377 if (!insn_state)
1378 return -ENOMEM;
1379
1380 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1381 if (!insn_stack) {
1382 kfree(insn_state);
1383 return -ENOMEM;
1384 }
1385
1386 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1387 insn_stack[0] = 0; /* 0 is the first instruction */
1388 cur_stack = 1;
1389
1390peek_stack:
1391 if (cur_stack == 0)
1392 goto check_state;
1393 t = insn_stack[cur_stack - 1];
1394
1395 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1396 u8 opcode = BPF_OP(insns[t].code);
1397
1398 if (opcode == BPF_EXIT) {
1399 goto mark_explored;
1400 } else if (opcode == BPF_CALL) {
1401 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1402 if (ret == 1)
1403 goto peek_stack;
1404 else if (ret < 0)
1405 goto err_free;
1406 } else if (opcode == BPF_JA) {
1407 if (BPF_SRC(insns[t].code) != BPF_K) {
1408 ret = -EINVAL;
1409 goto err_free;
1410 }
1411 /* unconditional jump with single edge */
1412 ret = push_insn(t, t + insns[t].off + 1,
1413 FALLTHROUGH, env);
1414 if (ret == 1)
1415 goto peek_stack;
1416 else if (ret < 0)
1417 goto err_free;
f1bca824
AS
1418 /* tell verifier to check for equivalent states
1419 * after every call and jump
1420 */
c3de6317
AS
1421 if (t + 1 < insn_cnt)
1422 env->explored_states[t + 1] = STATE_LIST_MARK;
475fb78f
AS
1423 } else {
1424 /* conditional jump with two edges */
1425 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1426 if (ret == 1)
1427 goto peek_stack;
1428 else if (ret < 0)
1429 goto err_free;
1430
1431 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1432 if (ret == 1)
1433 goto peek_stack;
1434 else if (ret < 0)
1435 goto err_free;
1436 }
1437 } else {
1438 /* all other non-branch instructions with single
1439 * fall-through edge
1440 */
1441 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1442 if (ret == 1)
1443 goto peek_stack;
1444 else if (ret < 0)
1445 goto err_free;
1446 }
1447
1448mark_explored:
1449 insn_state[t] = EXPLORED;
1450 if (cur_stack-- <= 0) {
1451 verbose("pop stack internal bug\n");
1452 ret = -EFAULT;
1453 goto err_free;
1454 }
1455 goto peek_stack;
1456
1457check_state:
1458 for (i = 0; i < insn_cnt; i++) {
1459 if (insn_state[i] != EXPLORED) {
1460 verbose("unreachable insn %d\n", i);
1461 ret = -EINVAL;
1462 goto err_free;
1463 }
1464 }
1465 ret = 0; /* cfg looks good */
1466
1467err_free:
1468 kfree(insn_state);
1469 kfree(insn_stack);
1470 return ret;
1471}
1472
f1bca824
AS
1473/* compare two verifier states
1474 *
1475 * all states stored in state_list are known to be valid, since
1476 * verifier reached 'bpf_exit' instruction through them
1477 *
1478 * this function is called when verifier exploring different branches of
1479 * execution popped from the state stack. If it sees an old state that has
1480 * more strict register state and more strict stack state then this execution
1481 * branch doesn't need to be explored further, since verifier already
1482 * concluded that more strict state leads to valid finish.
1483 *
1484 * Therefore two states are equivalent if register state is more conservative
1485 * and explored stack state is more conservative than the current one.
1486 * Example:
1487 * explored current
1488 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1489 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1490 *
1491 * In other words if current stack state (one being explored) has more
1492 * valid slots than old one that already passed validation, it means
1493 * the verifier can stop exploring and conclude that current state is valid too
1494 *
1495 * Similarly with registers. If explored state has register type as invalid
1496 * whereas register type in current state is meaningful, it means that
1497 * the current state will reach 'bpf_exit' instruction safely
1498 */
1499static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1500{
1501 int i;
1502
1503 for (i = 0; i < MAX_BPF_REG; i++) {
1504 if (memcmp(&old->regs[i], &cur->regs[i],
1505 sizeof(old->regs[0])) != 0) {
1506 if (old->regs[i].type == NOT_INIT ||
32bf08a6
AS
1507 (old->regs[i].type == UNKNOWN_VALUE &&
1508 cur->regs[i].type != NOT_INIT))
f1bca824
AS
1509 continue;
1510 return false;
1511 }
1512 }
1513
1514 for (i = 0; i < MAX_BPF_STACK; i++) {
9c399760
AS
1515 if (old->stack_slot_type[i] == STACK_INVALID)
1516 continue;
1517 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1518 /* Ex: old explored (safe) state has STACK_SPILL in
1519 * this stack slot, but current has has STACK_MISC ->
1520 * this verifier states are not equivalent,
1521 * return false to continue verification of this path
1522 */
f1bca824 1523 return false;
9c399760
AS
1524 if (i % BPF_REG_SIZE)
1525 continue;
1526 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1527 &cur->spilled_regs[i / BPF_REG_SIZE],
1528 sizeof(old->spilled_regs[0])))
1529 /* when explored and current stack slot types are
1530 * the same, check that stored pointers types
1531 * are the same as well.
1532 * Ex: explored safe path could have stored
1533 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1534 * but current path has stored:
1535 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1536 * such verifier states are not equivalent.
1537 * return false to continue verification of this path
1538 */
1539 return false;
1540 else
1541 continue;
f1bca824
AS
1542 }
1543 return true;
1544}
1545
1546static int is_state_visited(struct verifier_env *env, int insn_idx)
1547{
1548 struct verifier_state_list *new_sl;
1549 struct verifier_state_list *sl;
1550
1551 sl = env->explored_states[insn_idx];
1552 if (!sl)
1553 /* this 'insn_idx' instruction wasn't marked, so we will not
1554 * be doing state search here
1555 */
1556 return 0;
1557
1558 while (sl != STATE_LIST_MARK) {
1559 if (states_equal(&sl->state, &env->cur_state))
1560 /* reached equivalent register/stack state,
1561 * prune the search
1562 */
1563 return 1;
1564 sl = sl->next;
1565 }
1566
1567 /* there were no equivalent states, remember current one.
1568 * technically the current state is not proven to be safe yet,
1569 * but it will either reach bpf_exit (which means it's safe) or
1570 * it will be rejected. Since there are no loops, we won't be
1571 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1572 */
1573 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1574 if (!new_sl)
1575 return -ENOMEM;
1576
1577 /* add new state to the head of linked list */
1578 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1579 new_sl->next = env->explored_states[insn_idx];
1580 env->explored_states[insn_idx] = new_sl;
1581 return 0;
1582}
1583
17a52670
AS
1584static int do_check(struct verifier_env *env)
1585{
1586 struct verifier_state *state = &env->cur_state;
1587 struct bpf_insn *insns = env->prog->insnsi;
1588 struct reg_state *regs = state->regs;
1589 int insn_cnt = env->prog->len;
1590 int insn_idx, prev_insn_idx = 0;
1591 int insn_processed = 0;
1592 bool do_print_state = false;
1593
1594 init_reg_state(regs);
1595 insn_idx = 0;
1596 for (;;) {
1597 struct bpf_insn *insn;
1598 u8 class;
1599 int err;
1600
1601 if (insn_idx >= insn_cnt) {
1602 verbose("invalid insn idx %d insn_cnt %d\n",
1603 insn_idx, insn_cnt);
1604 return -EFAULT;
1605 }
1606
1607 insn = &insns[insn_idx];
1608 class = BPF_CLASS(insn->code);
1609
1610 if (++insn_processed > 32768) {
1611 verbose("BPF program is too large. Proccessed %d insn\n",
1612 insn_processed);
1613 return -E2BIG;
1614 }
1615
f1bca824
AS
1616 err = is_state_visited(env, insn_idx);
1617 if (err < 0)
1618 return err;
1619 if (err == 1) {
1620 /* found equivalent state, can prune the search */
1621 if (log_level) {
1622 if (do_print_state)
1623 verbose("\nfrom %d to %d: safe\n",
1624 prev_insn_idx, insn_idx);
1625 else
1626 verbose("%d: safe\n", insn_idx);
1627 }
1628 goto process_bpf_exit;
1629 }
1630
17a52670
AS
1631 if (log_level && do_print_state) {
1632 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1633 print_verifier_state(env);
1634 do_print_state = false;
1635 }
1636
1637 if (log_level) {
1638 verbose("%d: ", insn_idx);
1639 print_bpf_insn(insn);
1640 }
1641
1642 if (class == BPF_ALU || class == BPF_ALU64) {
1643 err = check_alu_op(regs, insn);
1644 if (err)
1645 return err;
1646
1647 } else if (class == BPF_LDX) {
9bac3d6d
AS
1648 enum bpf_reg_type src_reg_type;
1649
1650 /* check for reserved fields is already done */
1651
17a52670
AS
1652 /* check src operand */
1653 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1654 if (err)
1655 return err;
1656
1657 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1658 if (err)
1659 return err;
1660
725f9dcd
AS
1661 src_reg_type = regs[insn->src_reg].type;
1662
17a52670
AS
1663 /* check that memory (src_reg + off) is readable,
1664 * the state of dst_reg will be updated by this func
1665 */
1666 err = check_mem_access(env, insn->src_reg, insn->off,
1667 BPF_SIZE(insn->code), BPF_READ,
1668 insn->dst_reg);
1669 if (err)
1670 return err;
1671
725f9dcd
AS
1672 if (BPF_SIZE(insn->code) != BPF_W) {
1673 insn_idx++;
1674 continue;
1675 }
9bac3d6d 1676
725f9dcd 1677 if (insn->imm == 0) {
9bac3d6d
AS
1678 /* saw a valid insn
1679 * dst_reg = *(u32 *)(src_reg + off)
1680 * use reserved 'imm' field to mark this insn
1681 */
1682 insn->imm = src_reg_type;
1683
1684 } else if (src_reg_type != insn->imm &&
1685 (src_reg_type == PTR_TO_CTX ||
1686 insn->imm == PTR_TO_CTX)) {
1687 /* ABuser program is trying to use the same insn
1688 * dst_reg = *(u32*) (src_reg + off)
1689 * with different pointer types:
1690 * src_reg == ctx in one branch and
1691 * src_reg == stack|map in some other branch.
1692 * Reject it.
1693 */
1694 verbose("same insn cannot be used with different pointers\n");
1695 return -EINVAL;
1696 }
1697
17a52670 1698 } else if (class == BPF_STX) {
d691f9e8
AS
1699 enum bpf_reg_type dst_reg_type;
1700
17a52670
AS
1701 if (BPF_MODE(insn->code) == BPF_XADD) {
1702 err = check_xadd(env, insn);
1703 if (err)
1704 return err;
1705 insn_idx++;
1706 continue;
1707 }
1708
17a52670
AS
1709 /* check src1 operand */
1710 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1711 if (err)
1712 return err;
1713 /* check src2 operand */
1714 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1715 if (err)
1716 return err;
1717
d691f9e8
AS
1718 dst_reg_type = regs[insn->dst_reg].type;
1719
17a52670
AS
1720 /* check that memory (dst_reg + off) is writeable */
1721 err = check_mem_access(env, insn->dst_reg, insn->off,
1722 BPF_SIZE(insn->code), BPF_WRITE,
1723 insn->src_reg);
1724 if (err)
1725 return err;
1726
d691f9e8
AS
1727 if (insn->imm == 0) {
1728 insn->imm = dst_reg_type;
1729 } else if (dst_reg_type != insn->imm &&
1730 (dst_reg_type == PTR_TO_CTX ||
1731 insn->imm == PTR_TO_CTX)) {
1732 verbose("same insn cannot be used with different pointers\n");
1733 return -EINVAL;
1734 }
1735
17a52670
AS
1736 } else if (class == BPF_ST) {
1737 if (BPF_MODE(insn->code) != BPF_MEM ||
1738 insn->src_reg != BPF_REG_0) {
1739 verbose("BPF_ST uses reserved fields\n");
1740 return -EINVAL;
1741 }
1742 /* check src operand */
1743 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1744 if (err)
1745 return err;
1746
1747 /* check that memory (dst_reg + off) is writeable */
1748 err = check_mem_access(env, insn->dst_reg, insn->off,
1749 BPF_SIZE(insn->code), BPF_WRITE,
1750 -1);
1751 if (err)
1752 return err;
1753
1754 } else if (class == BPF_JMP) {
1755 u8 opcode = BPF_OP(insn->code);
1756
1757 if (opcode == BPF_CALL) {
1758 if (BPF_SRC(insn->code) != BPF_K ||
1759 insn->off != 0 ||
1760 insn->src_reg != BPF_REG_0 ||
1761 insn->dst_reg != BPF_REG_0) {
1762 verbose("BPF_CALL uses reserved fields\n");
1763 return -EINVAL;
1764 }
1765
1766 err = check_call(env, insn->imm);
1767 if (err)
1768 return err;
1769
1770 } else if (opcode == BPF_JA) {
1771 if (BPF_SRC(insn->code) != BPF_K ||
1772 insn->imm != 0 ||
1773 insn->src_reg != BPF_REG_0 ||
1774 insn->dst_reg != BPF_REG_0) {
1775 verbose("BPF_JA uses reserved fields\n");
1776 return -EINVAL;
1777 }
1778
1779 insn_idx += insn->off + 1;
1780 continue;
1781
1782 } else if (opcode == BPF_EXIT) {
1783 if (BPF_SRC(insn->code) != BPF_K ||
1784 insn->imm != 0 ||
1785 insn->src_reg != BPF_REG_0 ||
1786 insn->dst_reg != BPF_REG_0) {
1787 verbose("BPF_EXIT uses reserved fields\n");
1788 return -EINVAL;
1789 }
1790
1791 /* eBPF calling convetion is such that R0 is used
1792 * to return the value from eBPF program.
1793 * Make sure that it's readable at this time
1794 * of bpf_exit, which means that program wrote
1795 * something into it earlier
1796 */
1797 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1798 if (err)
1799 return err;
1800
f1bca824 1801process_bpf_exit:
17a52670
AS
1802 insn_idx = pop_stack(env, &prev_insn_idx);
1803 if (insn_idx < 0) {
1804 break;
1805 } else {
1806 do_print_state = true;
1807 continue;
1808 }
1809 } else {
1810 err = check_cond_jmp_op(env, insn, &insn_idx);
1811 if (err)
1812 return err;
1813 }
1814 } else if (class == BPF_LD) {
1815 u8 mode = BPF_MODE(insn->code);
1816
1817 if (mode == BPF_ABS || mode == BPF_IND) {
ddd872bc
AS
1818 err = check_ld_abs(env, insn);
1819 if (err)
1820 return err;
1821
17a52670
AS
1822 } else if (mode == BPF_IMM) {
1823 err = check_ld_imm(env, insn);
1824 if (err)
1825 return err;
1826
1827 insn_idx++;
1828 } else {
1829 verbose("invalid BPF_LD mode\n");
1830 return -EINVAL;
1831 }
1832 } else {
1833 verbose("unknown insn class %d\n", class);
1834 return -EINVAL;
1835 }
1836
1837 insn_idx++;
1838 }
1839
1840 return 0;
1841}
1842
0246e64d
AS
1843/* look for pseudo eBPF instructions that access map FDs and
1844 * replace them with actual map pointers
1845 */
1846static int replace_map_fd_with_map_ptr(struct verifier_env *env)
1847{
1848 struct bpf_insn *insn = env->prog->insnsi;
1849 int insn_cnt = env->prog->len;
1850 int i, j;
1851
1852 for (i = 0; i < insn_cnt; i++, insn++) {
9bac3d6d 1853 if (BPF_CLASS(insn->code) == BPF_LDX &&
d691f9e8 1854 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
9bac3d6d
AS
1855 verbose("BPF_LDX uses reserved fields\n");
1856 return -EINVAL;
1857 }
1858
d691f9e8
AS
1859 if (BPF_CLASS(insn->code) == BPF_STX &&
1860 ((BPF_MODE(insn->code) != BPF_MEM &&
1861 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
1862 verbose("BPF_STX uses reserved fields\n");
1863 return -EINVAL;
1864 }
1865
0246e64d
AS
1866 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
1867 struct bpf_map *map;
1868 struct fd f;
1869
1870 if (i == insn_cnt - 1 || insn[1].code != 0 ||
1871 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
1872 insn[1].off != 0) {
1873 verbose("invalid bpf_ld_imm64 insn\n");
1874 return -EINVAL;
1875 }
1876
1877 if (insn->src_reg == 0)
1878 /* valid generic load 64-bit imm */
1879 goto next_insn;
1880
1881 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
1882 verbose("unrecognized bpf_ld_imm64 insn\n");
1883 return -EINVAL;
1884 }
1885
1886 f = fdget(insn->imm);
1887
1888 map = bpf_map_get(f);
1889 if (IS_ERR(map)) {
1890 verbose("fd %d is not pointing to valid bpf_map\n",
1891 insn->imm);
1892 fdput(f);
1893 return PTR_ERR(map);
1894 }
1895
1896 /* store map pointer inside BPF_LD_IMM64 instruction */
1897 insn[0].imm = (u32) (unsigned long) map;
1898 insn[1].imm = ((u64) (unsigned long) map) >> 32;
1899
1900 /* check whether we recorded this map already */
1901 for (j = 0; j < env->used_map_cnt; j++)
1902 if (env->used_maps[j] == map) {
1903 fdput(f);
1904 goto next_insn;
1905 }
1906
1907 if (env->used_map_cnt >= MAX_USED_MAPS) {
1908 fdput(f);
1909 return -E2BIG;
1910 }
1911
1912 /* remember this map */
1913 env->used_maps[env->used_map_cnt++] = map;
1914
1915 /* hold the map. If the program is rejected by verifier,
1916 * the map will be released by release_maps() or it
1917 * will be used by the valid program until it's unloaded
1918 * and all maps are released in free_bpf_prog_info()
1919 */
1920 atomic_inc(&map->refcnt);
1921
1922 fdput(f);
1923next_insn:
1924 insn++;
1925 i++;
1926 }
1927 }
1928
1929 /* now all pseudo BPF_LD_IMM64 instructions load valid
1930 * 'struct bpf_map *' into a register instead of user map_fd.
1931 * These pointers will be used later by verifier to validate map access.
1932 */
1933 return 0;
1934}
1935
1936/* drop refcnt of maps used by the rejected program */
1937static void release_maps(struct verifier_env *env)
1938{
1939 int i;
1940
1941 for (i = 0; i < env->used_map_cnt; i++)
1942 bpf_map_put(env->used_maps[i]);
1943}
1944
1945/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
1946static void convert_pseudo_ld_imm64(struct verifier_env *env)
1947{
1948 struct bpf_insn *insn = env->prog->insnsi;
1949 int insn_cnt = env->prog->len;
1950 int i;
1951
1952 for (i = 0; i < insn_cnt; i++, insn++)
1953 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
1954 insn->src_reg = 0;
1955}
1956
9bac3d6d
AS
1957static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
1958{
1959 struct bpf_insn *insn = prog->insnsi;
1960 int insn_cnt = prog->len;
1961 int i;
1962
1963 for (i = 0; i < insn_cnt; i++, insn++) {
1964 if (BPF_CLASS(insn->code) != BPF_JMP ||
1965 BPF_OP(insn->code) == BPF_CALL ||
1966 BPF_OP(insn->code) == BPF_EXIT)
1967 continue;
1968
1969 /* adjust offset of jmps if necessary */
1970 if (i < pos && i + insn->off + 1 > pos)
1971 insn->off += delta;
1972 else if (i > pos && i + insn->off + 1 < pos)
1973 insn->off -= delta;
1974 }
1975}
1976
1977/* convert load instructions that access fields of 'struct __sk_buff'
1978 * into sequence of instructions that access fields of 'struct sk_buff'
1979 */
1980static int convert_ctx_accesses(struct verifier_env *env)
1981{
1982 struct bpf_insn *insn = env->prog->insnsi;
1983 int insn_cnt = env->prog->len;
1984 struct bpf_insn insn_buf[16];
1985 struct bpf_prog *new_prog;
1986 u32 cnt;
1987 int i;
d691f9e8 1988 enum bpf_access_type type;
9bac3d6d
AS
1989
1990 if (!env->prog->aux->ops->convert_ctx_access)
1991 return 0;
1992
1993 for (i = 0; i < insn_cnt; i++, insn++) {
d691f9e8
AS
1994 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
1995 type = BPF_READ;
1996 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
1997 type = BPF_WRITE;
1998 else
9bac3d6d
AS
1999 continue;
2000
2001 if (insn->imm != PTR_TO_CTX) {
2002 /* clear internal mark */
2003 insn->imm = 0;
2004 continue;
2005 }
2006
2007 cnt = env->prog->aux->ops->
d691f9e8 2008 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
9bac3d6d
AS
2009 insn->off, insn_buf);
2010 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2011 verbose("bpf verifier is misconfigured\n");
2012 return -EINVAL;
2013 }
2014
2015 if (cnt == 1) {
2016 memcpy(insn, insn_buf, sizeof(*insn));
2017 continue;
2018 }
2019
2020 /* several new insns need to be inserted. Make room for them */
2021 insn_cnt += cnt - 1;
2022 new_prog = bpf_prog_realloc(env->prog,
2023 bpf_prog_size(insn_cnt),
2024 GFP_USER);
2025 if (!new_prog)
2026 return -ENOMEM;
2027
2028 new_prog->len = insn_cnt;
2029
2030 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2031 sizeof(*insn) * (insn_cnt - i - cnt));
2032
2033 /* copy substitute insns in place of load instruction */
2034 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2035
2036 /* adjust branches in the whole program */
2037 adjust_branches(new_prog, i, cnt - 1);
2038
2039 /* keep walking new program and skip insns we just inserted */
2040 env->prog = new_prog;
2041 insn = new_prog->insnsi + i + cnt - 1;
2042 i += cnt - 1;
2043 }
2044
2045 return 0;
2046}
2047
f1bca824
AS
2048static void free_states(struct verifier_env *env)
2049{
2050 struct verifier_state_list *sl, *sln;
2051 int i;
2052
2053 if (!env->explored_states)
2054 return;
2055
2056 for (i = 0; i < env->prog->len; i++) {
2057 sl = env->explored_states[i];
2058
2059 if (sl)
2060 while (sl != STATE_LIST_MARK) {
2061 sln = sl->next;
2062 kfree(sl);
2063 sl = sln;
2064 }
2065 }
2066
2067 kfree(env->explored_states);
2068}
2069
9bac3d6d 2070int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
51580e79 2071{
cbd35700
AS
2072 char __user *log_ubuf = NULL;
2073 struct verifier_env *env;
51580e79
AS
2074 int ret = -EINVAL;
2075
9bac3d6d 2076 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
cbd35700
AS
2077 return -E2BIG;
2078
2079 /* 'struct verifier_env' can be global, but since it's not small,
2080 * allocate/free it every time bpf_check() is called
2081 */
2082 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2083 if (!env)
2084 return -ENOMEM;
2085
9bac3d6d 2086 env->prog = *prog;
0246e64d 2087
cbd35700
AS
2088 /* grab the mutex to protect few globals used by verifier */
2089 mutex_lock(&bpf_verifier_lock);
2090
2091 if (attr->log_level || attr->log_buf || attr->log_size) {
2092 /* user requested verbose verifier output
2093 * and supplied buffer to store the verification trace
2094 */
2095 log_level = attr->log_level;
2096 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2097 log_size = attr->log_size;
2098 log_len = 0;
2099
2100 ret = -EINVAL;
2101 /* log_* values have to be sane */
2102 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2103 log_level == 0 || log_ubuf == NULL)
2104 goto free_env;
2105
2106 ret = -ENOMEM;
2107 log_buf = vmalloc(log_size);
2108 if (!log_buf)
2109 goto free_env;
2110 } else {
2111 log_level = 0;
2112 }
2113
0246e64d
AS
2114 ret = replace_map_fd_with_map_ptr(env);
2115 if (ret < 0)
2116 goto skip_full_check;
2117
9bac3d6d 2118 env->explored_states = kcalloc(env->prog->len,
f1bca824
AS
2119 sizeof(struct verifier_state_list *),
2120 GFP_USER);
2121 ret = -ENOMEM;
2122 if (!env->explored_states)
2123 goto skip_full_check;
2124
475fb78f
AS
2125 ret = check_cfg(env);
2126 if (ret < 0)
2127 goto skip_full_check;
2128
17a52670 2129 ret = do_check(env);
cbd35700 2130
0246e64d 2131skip_full_check:
17a52670 2132 while (pop_stack(env, NULL) >= 0);
f1bca824 2133 free_states(env);
0246e64d 2134
9bac3d6d
AS
2135 if (ret == 0)
2136 /* program is valid, convert *(u32*)(ctx + off) accesses */
2137 ret = convert_ctx_accesses(env);
2138
cbd35700
AS
2139 if (log_level && log_len >= log_size - 1) {
2140 BUG_ON(log_len >= log_size);
2141 /* verifier log exceeded user supplied buffer */
2142 ret = -ENOSPC;
2143 /* fall through to return what was recorded */
2144 }
2145
2146 /* copy verifier log back to user space including trailing zero */
2147 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2148 ret = -EFAULT;
2149 goto free_log_buf;
2150 }
2151
0246e64d
AS
2152 if (ret == 0 && env->used_map_cnt) {
2153 /* if program passed verifier, update used_maps in bpf_prog_info */
9bac3d6d
AS
2154 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2155 sizeof(env->used_maps[0]),
2156 GFP_KERNEL);
0246e64d 2157
9bac3d6d 2158 if (!env->prog->aux->used_maps) {
0246e64d
AS
2159 ret = -ENOMEM;
2160 goto free_log_buf;
2161 }
2162
9bac3d6d 2163 memcpy(env->prog->aux->used_maps, env->used_maps,
0246e64d 2164 sizeof(env->used_maps[0]) * env->used_map_cnt);
9bac3d6d 2165 env->prog->aux->used_map_cnt = env->used_map_cnt;
0246e64d
AS
2166
2167 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2168 * bpf_ld_imm64 instructions
2169 */
2170 convert_pseudo_ld_imm64(env);
2171 }
cbd35700
AS
2172
2173free_log_buf:
2174 if (log_level)
2175 vfree(log_buf);
2176free_env:
9bac3d6d 2177 if (!env->prog->aux->used_maps)
0246e64d
AS
2178 /* if we didn't copy map pointers into bpf_prog_info, release
2179 * them now. Otherwise free_bpf_prog_info() will release them.
2180 */
2181 release_maps(env);
9bac3d6d 2182 *prog = env->prog;
cbd35700
AS
2183 kfree(env);
2184 mutex_unlock(&bpf_verifier_lock);
51580e79
AS
2185 return ret;
2186}