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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 */
156 STACK_SPILL, /* 1st byte of register spilled into stack */
157 STACK_SPILL_PART, /* other 7 bytes of register spill */
158 STACK_MISC /* BPF program wrote some data into this slot */
159};
160
161struct bpf_stack_slot {
162 enum bpf_stack_slot_type stype;
163 struct reg_state reg_st;
164};
165
166/* state of the program:
167 * type of all registers and stack info
168 */
169struct verifier_state {
170 struct reg_state regs[MAX_BPF_REG];
171 struct bpf_stack_slot stack[MAX_BPF_STACK];
172};
173
174/* linked list of verifier states used to prune search */
175struct verifier_state_list {
176 struct verifier_state state;
177 struct verifier_state_list *next;
178};
179
180/* verifier_state + insn_idx are pushed to stack when branch is encountered */
181struct verifier_stack_elem {
182 /* verifer state is 'st'
183 * before processing instruction 'insn_idx'
184 * and after processing instruction 'prev_insn_idx'
185 */
186 struct verifier_state st;
187 int insn_idx;
188 int prev_insn_idx;
189 struct verifier_stack_elem *next;
190};
191
0246e64d
AS		 192#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
193
cbd35700
AS		 194/* single container for all structs
195 * one verifier_env per bpf_check() call
196 */
197struct verifier_env {
0246e64d 198 struct bpf_prog *prog; /* eBPF program being verified */
17a52670
AS		 199 struct verifier_stack_elem *head; /* stack of verifier states to be processed */
200 int stack_size; /* number of states to be processed */
201 struct verifier_state cur_state; /* current verifier state */
f1bca824 202 struct verifier_state_list **explored_states; /* search pruning optimization */
0246e64d
AS		 203 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
204 u32 used_map_cnt; /* number of used maps */
cbd35700
AS		 205};
206
207/* verbose verifier prints what it's seeing
208 * bpf_check() is called under lock, so no race to access these global vars
209 */
210static u32 log_level, log_size, log_len;
211static char *log_buf;
212
213static DEFINE_MUTEX(bpf_verifier_lock);
214
215/* log_level controls verbosity level of eBPF verifier.
216 * verbose() is used to dump the verification trace to the log, so the user
217 * can figure out what's wrong with the program
218 */
219static void verbose(const char *fmt, ...)
220{
221 va_list args;
222
223 if (log_level == 0 || log_len >= log_size - 1)
224 return;
225
226 va_start(args, fmt);
227 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
228 va_end(args);
229}
230
17a52670
AS		 231/* string representation of 'enum bpf_reg_type' */
232static const char * const reg_type_str[] = {
233 [NOT_INIT] = "?",
234 [UNKNOWN_VALUE] = "inv",
235 [PTR_TO_CTX] = "ctx",
236 [CONST_PTR_TO_MAP] = "map_ptr",
237 [PTR_TO_MAP_VALUE] = "map_value",
238 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
239 [FRAME_PTR] = "fp",
240 [PTR_TO_STACK] = "fp",
241 [CONST_IMM] = "imm",
242};
243
244static void print_verifier_state(struct verifier_env *env)
245{
246 enum bpf_reg_type t;
247 int i;
248
249 for (i = 0; i < MAX_BPF_REG; i++) {
250 t = env->cur_state.regs[i].type;
251 if (t == NOT_INIT)
252 continue;
253 verbose(" R%d=%s", i, reg_type_str[t]);
254 if (t == CONST_IMM || t == PTR_TO_STACK)
255 verbose("%d", env->cur_state.regs[i].imm);
256 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
257 t == PTR_TO_MAP_VALUE_OR_NULL)
258 verbose("(ks=%d,vs=%d)",
259 env->cur_state.regs[i].map_ptr->key_size,
260 env->cur_state.regs[i].map_ptr->value_size);
261 }
262 for (i = 0; i < MAX_BPF_STACK; i++) {
263 if (env->cur_state.stack[i].stype == STACK_SPILL)
264 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
265 reg_type_str[env->cur_state.stack[i].reg_st.type]);
266 }
267 verbose("\n");
268}
269
cbd35700
AS		 270static const char *const bpf_class_string[] = {
271 [BPF_LD] = "ld",
272 [BPF_LDX] = "ldx",
273 [BPF_ST] = "st",
274 [BPF_STX] = "stx",
275 [BPF_ALU] = "alu",
276 [BPF_JMP] = "jmp",
277 [BPF_RET] = "BUG",
278 [BPF_ALU64] = "alu64",
279};
280
281static const char *const bpf_alu_string[] = {
282 [BPF_ADD >> 4] = "+=",
283 [BPF_SUB >> 4] = "-=",
284 [BPF_MUL >> 4] = "*=",
285 [BPF_DIV >> 4] = "/=",
286 [BPF_OR >> 4] = "|=",
287 [BPF_AND >> 4] = "&=",
288 [BPF_LSH >> 4] = "<<=",
289 [BPF_RSH >> 4] = ">>=",
290 [BPF_NEG >> 4] = "neg",
291 [BPF_MOD >> 4] = "%=",
292 [BPF_XOR >> 4] = "^=",
293 [BPF_MOV >> 4] = "=",
294 [BPF_ARSH >> 4] = "s>>=",
295 [BPF_END >> 4] = "endian",
296};
297
298static const char *const bpf_ldst_string[] = {
299 [BPF_W >> 3] = "u32",
300 [BPF_H >> 3] = "u16",
301 [BPF_B >> 3] = "u8",
302 [BPF_DW >> 3] = "u64",
303};
304
305static const char *const bpf_jmp_string[] = {
306 [BPF_JA >> 4] = "jmp",
307 [BPF_JEQ >> 4] = "==",
308 [BPF_JGT >> 4] = ">",
309 [BPF_JGE >> 4] = ">=",
310 [BPF_JSET >> 4] = "&",
311 [BPF_JNE >> 4] = "!=",
312 [BPF_JSGT >> 4] = "s>",
313 [BPF_JSGE >> 4] = "s>=",
314 [BPF_CALL >> 4] = "call",
315 [BPF_EXIT >> 4] = "exit",
316};
317
318static void print_bpf_insn(struct bpf_insn *insn)
319{
320 u8 class = BPF_CLASS(insn->code);
321
322 if (class == BPF_ALU || class == BPF_ALU64) {
323 if (BPF_SRC(insn->code) == BPF_X)
324 verbose("(%02x) %sr%d %s %sr%d\n",
325 insn->code, class == BPF_ALU ? "(u32) " : "",
326 insn->dst_reg,
327 bpf_alu_string[BPF_OP(insn->code) >> 4],
328 class == BPF_ALU ? "(u32) " : "",
329 insn->src_reg);
330 else
331 verbose("(%02x) %sr%d %s %s%d\n",
332 insn->code, class == BPF_ALU ? "(u32) " : "",
333 insn->dst_reg,
334 bpf_alu_string[BPF_OP(insn->code) >> 4],
335 class == BPF_ALU ? "(u32) " : "",
336 insn->imm);
337 } else if (class == BPF_STX) {
338 if (BPF_MODE(insn->code) == BPF_MEM)
339 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
340 insn->code,
341 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
342 insn->dst_reg,
343 insn->off, insn->src_reg);
344 else if (BPF_MODE(insn->code) == BPF_XADD)
345 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
346 insn->code,
347 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
348 insn->dst_reg, insn->off,
349 insn->src_reg);
350 else
351 verbose("BUG_%02x\n", insn->code);
352 } else if (class == BPF_ST) {
353 if (BPF_MODE(insn->code) != BPF_MEM) {
354 verbose("BUG_st_%02x\n", insn->code);
355 return;
356 }
357 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
358 insn->code,
359 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
360 insn->dst_reg,
361 insn->off, insn->imm);
362 } else if (class == BPF_LDX) {
363 if (BPF_MODE(insn->code) != BPF_MEM) {
364 verbose("BUG_ldx_%02x\n", insn->code);
365 return;
366 }
367 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
368 insn->code, insn->dst_reg,
369 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
370 insn->src_reg, insn->off);
371 } else if (class == BPF_LD) {
372 if (BPF_MODE(insn->code) == BPF_ABS) {
373 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
374 insn->code,
375 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
376 insn->imm);
377 } else if (BPF_MODE(insn->code) == BPF_IND) {
378 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
379 insn->code,
380 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
381 insn->src_reg, insn->imm);
382 } else if (BPF_MODE(insn->code) == BPF_IMM) {
383 verbose("(%02x) r%d = 0x%x\n",
384 insn->code, insn->dst_reg, insn->imm);
385 } else {
386 verbose("BUG_ld_%02x\n", insn->code);
387 return;
388 }
389 } else if (class == BPF_JMP) {
390 u8 opcode = BPF_OP(insn->code);
391
392 if (opcode == BPF_CALL) {
393 verbose("(%02x) call %d\n", insn->code, insn->imm);
394 } else if (insn->code == (BPF_JMP | BPF_JA)) {
395 verbose("(%02x) goto pc%+d\n",
396 insn->code, insn->off);
397 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
398 verbose("(%02x) exit\n", insn->code);
399 } else if (BPF_SRC(insn->code) == BPF_X) {
400 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
401 insn->code, insn->dst_reg,
402 bpf_jmp_string[BPF_OP(insn->code) >> 4],
403 insn->src_reg, insn->off);
404 } else {
405 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
406 insn->code, insn->dst_reg,
407 bpf_jmp_string[BPF_OP(insn->code) >> 4],
408 insn->imm, insn->off);
409 }
410 } else {
411 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
412 }
413}
414
17a52670
AS		 415static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
416{
417 struct verifier_stack_elem *elem;
418 int insn_idx;
419
420 if (env->head == NULL)
421 return -1;
422
423 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
424 insn_idx = env->head->insn_idx;
425 if (prev_insn_idx)
426 *prev_insn_idx = env->head->prev_insn_idx;
427 elem = env->head->next;
428 kfree(env->head);
429 env->head = elem;
430 env->stack_size--;
431 return insn_idx;
432}
433
434static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
435 int prev_insn_idx)
436{
437 struct verifier_stack_elem *elem;
438
439 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
440 if (!elem)
441 goto err;
442
443 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
444 elem->insn_idx = insn_idx;
445 elem->prev_insn_idx = prev_insn_idx;
446 elem->next = env->head;
447 env->head = elem;
448 env->stack_size++;
449 if (env->stack_size > 1024) {
450 verbose("BPF program is too complex\n");
451 goto err;
452 }
453 return &elem->st;
454err:
455 /* pop all elements and return */
456 while (pop_stack(env, NULL) >= 0);
457 return NULL;
458}
459
460#define CALLER_SAVED_REGS 6
461static const int caller_saved[CALLER_SAVED_REGS] = {
462 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
463};
464
465static void init_reg_state(struct reg_state *regs)
466{
467 int i;
468
469 for (i = 0; i < MAX_BPF_REG; i++) {
470 regs[i].type = NOT_INIT;
471 regs[i].imm = 0;
472 regs[i].map_ptr = NULL;
473 }
474
475 /* frame pointer */
476 regs[BPF_REG_FP].type = FRAME_PTR;
477
478 /* 1st arg to a function */
479 regs[BPF_REG_1].type = PTR_TO_CTX;
480}
481
482static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
483{
484 BUG_ON(regno >= MAX_BPF_REG);
485 regs[regno].type = UNKNOWN_VALUE;
486 regs[regno].imm = 0;
487 regs[regno].map_ptr = NULL;
488}
489
490enum reg_arg_type {
491 SRC_OP, /* register is used as source operand */
492 DST_OP, /* register is used as destination operand */
493 DST_OP_NO_MARK /* same as above, check only, don't mark */
494};
495
496static int check_reg_arg(struct reg_state *regs, u32 regno,
497 enum reg_arg_type t)
498{
499 if (regno >= MAX_BPF_REG) {
500 verbose("R%d is invalid\n", regno);
501 return -EINVAL;
502 }
503
504 if (t == SRC_OP) {
505 /* check whether register used as source operand can be read */
506 if (regs[regno].type == NOT_INIT) {
507 verbose("R%d !read_ok\n", regno);
508 return -EACCES;
509 }
510 } else {
511 /* check whether register used as dest operand can be written to */
512 if (regno == BPF_REG_FP) {
513 verbose("frame pointer is read only\n");
514 return -EACCES;
515 }
516 if (t == DST_OP)
517 mark_reg_unknown_value(regs, regno);
518 }
519 return 0;
520}
521
522static int bpf_size_to_bytes(int bpf_size)
523{
524 if (bpf_size == BPF_W)
525 return 4;
526 else if (bpf_size == BPF_H)
527 return 2;
528 else if (bpf_size == BPF_B)
529 return 1;
530 else if (bpf_size == BPF_DW)
531 return 8;
532 else
533 return -EINVAL;
534}
535
536/* check_stack_read/write functions track spill/fill of registers,
537 * stack boundary and alignment are checked in check_mem_access()
538 */
539static int check_stack_write(struct verifier_state *state, int off, int size,
540 int value_regno)
541{
542 struct bpf_stack_slot *slot;
543 int i;
544
545 if (value_regno >= 0 &&
546 (state->regs[value_regno].type == PTR_TO_MAP_VALUE ||
547 state->regs[value_regno].type == PTR_TO_STACK ||
548 state->regs[value_regno].type == PTR_TO_CTX)) {
549
550 /* register containing pointer is being spilled into stack */
551 if (size != 8) {
552 verbose("invalid size of register spill\n");
553 return -EACCES;
554 }
555
556 slot = &state->stack[MAX_BPF_STACK + off];
557 slot->stype = STACK_SPILL;
558 /* save register state */
559 slot->reg_st = state->regs[value_regno];
560 for (i = 1; i < 8; i++) {
561 slot = &state->stack[MAX_BPF_STACK + off + i];
562 slot->stype = STACK_SPILL_PART;
563 slot->reg_st.type = UNKNOWN_VALUE;
564 slot->reg_st.map_ptr = NULL;
565 }
566 } else {
567
568 /* regular write of data into stack */
569 for (i = 0; i < size; i++) {
570 slot = &state->stack[MAX_BPF_STACK + off + i];
571 slot->stype = STACK_MISC;
572 slot->reg_st.type = UNKNOWN_VALUE;
573 slot->reg_st.map_ptr = NULL;
574 }
575 }
576 return 0;
577}
578
579static int check_stack_read(struct verifier_state *state, int off, int size,
580 int value_regno)
581{
582 int i;
583 struct bpf_stack_slot *slot;
584
585 slot = &state->stack[MAX_BPF_STACK + off];
586
587 if (slot->stype == STACK_SPILL) {
588 if (size != 8) {
589 verbose("invalid size of register spill\n");
590 return -EACCES;
591 }
592 for (i = 1; i < 8; i++) {
593 if (state->stack[MAX_BPF_STACK + off + i].stype !=
594 STACK_SPILL_PART) {
595 verbose("corrupted spill memory\n");
596 return -EACCES;
597 }
598 }
599
600 if (value_regno >= 0)
601 /* restore register state from stack */
602 state->regs[value_regno] = slot->reg_st;
603 return 0;
604 } else {
605 for (i = 0; i < size; i++) {
606 if (state->stack[MAX_BPF_STACK + off + i].stype !=
607 STACK_MISC) {
608 verbose("invalid read from stack off %d+%d size %d\n",
609 off, i, size);
610 return -EACCES;
611 }
612 }
613 if (value_regno >= 0)
614 /* have read misc data from the stack */
615 mark_reg_unknown_value(state->regs, value_regno);
616 return 0;
617 }
618}
619
620/* check read/write into map element returned by bpf_map_lookup_elem() */
621static int check_map_access(struct verifier_env *env, u32 regno, int off,
622 int size)
623{
624 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
625
626 if (off < 0 || off + size > map->value_size) {
627 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
628 map->value_size, off, size);
629 return -EACCES;
630 }
631 return 0;
632}
633
634/* check access to 'struct bpf_context' fields */
635static int check_ctx_access(struct verifier_env *env, int off, int size,
636 enum bpf_access_type t)
637{
638 if (env->prog->aux->ops->is_valid_access &&
639 env->prog->aux->ops->is_valid_access(off, size, t))
640 return 0;
641
642 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
643 return -EACCES;
644}
645
646/* check whether memory at (regno + off) is accessible for t = (read | write)
647 * if t==write, value_regno is a register which value is stored into memory
648 * if t==read, value_regno is a register which will receive the value from memory
649 * if t==write && value_regno==-1, some unknown value is stored into memory
650 * if t==read && value_regno==-1, don't care what we read from memory
651 */
652static int check_mem_access(struct verifier_env *env, u32 regno, int off,
653 int bpf_size, enum bpf_access_type t,
654 int value_regno)
655{
656 struct verifier_state *state = &env->cur_state;
657 int size, err = 0;
658
659 size = bpf_size_to_bytes(bpf_size);
660 if (size < 0)
661 return size;
662
663 if (off % size != 0) {
664 verbose("misaligned access off %d size %d\n", off, size);
665 return -EACCES;
666 }
667
668 if (state->regs[regno].type == PTR_TO_MAP_VALUE) {
669 err = check_map_access(env, regno, off, size);
670 if (!err && t == BPF_READ && value_regno >= 0)
671 mark_reg_unknown_value(state->regs, value_regno);
672
673 } else if (state->regs[regno].type == PTR_TO_CTX) {
674 err = check_ctx_access(env, off, size, t);
675 if (!err && t == BPF_READ && value_regno >= 0)
676 mark_reg_unknown_value(state->regs, value_regno);
677
678 } else if (state->regs[regno].type == FRAME_PTR) {
679 if (off >= 0 || off < -MAX_BPF_STACK) {
680 verbose("invalid stack off=%d size=%d\n", off, size);
681 return -EACCES;
682 }
683 if (t == BPF_WRITE)
684 err = check_stack_write(state, off, size, value_regno);
685 else
686 err = check_stack_read(state, off, size, value_regno);
687 } else {
688 verbose("R%d invalid mem access '%s'\n",
689 regno, reg_type_str[state->regs[regno].type]);
690 return -EACCES;
691 }
692 return err;
693}
694
695static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
696{
697 struct reg_state *regs = env->cur_state.regs;
698 int err;
699
700 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
701 insn->imm != 0) {
702 verbose("BPF_XADD uses reserved fields\n");
703 return -EINVAL;
704 }
705
706 /* check src1 operand */
707 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
708 if (err)
709 return err;
710
711 /* check src2 operand */
712 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
713 if (err)
714 return err;
715
716 /* check whether atomic_add can read the memory */
717 err = check_mem_access(env, insn->dst_reg, insn->off,
718 BPF_SIZE(insn->code), BPF_READ, -1);
719 if (err)
720 return err;
721
722 /* check whether atomic_add can write into the same memory */
723 return check_mem_access(env, insn->dst_reg, insn->off,
724 BPF_SIZE(insn->code), BPF_WRITE, -1);
725}
726
727/* when register 'regno' is passed into function that will read 'access_size'
728 * bytes from that pointer, make sure that it's within stack boundary
729 * and all elements of stack are initialized
730 */
731static int check_stack_boundary(struct verifier_env *env,
732 int regno, int access_size)
733{
734 struct verifier_state *state = &env->cur_state;
735 struct reg_state *regs = state->regs;
736 int off, i;
737
738 if (regs[regno].type != PTR_TO_STACK)
739 return -EACCES;
740
741 off = regs[regno].imm;
742 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
743 access_size <= 0) {
744 verbose("invalid stack type R%d off=%d access_size=%d\n",
745 regno, off, access_size);
746 return -EACCES;
747 }
748
749 for (i = 0; i < access_size; i++) {
750 if (state->stack[MAX_BPF_STACK + off + i].stype != STACK_MISC) {
751 verbose("invalid indirect read from stack off %d+%d size %d\n",
752 off, i, access_size);
753 return -EACCES;
754 }
755 }
756 return 0;
757}
758
759static int check_func_arg(struct verifier_env *env, u32 regno,
760 enum bpf_arg_type arg_type, struct bpf_map **mapp)
761{
762 struct reg_state *reg = env->cur_state.regs + regno;
763 enum bpf_reg_type expected_type;
764 int err = 0;
765
766 if (arg_type == ARG_ANYTHING)
767 return 0;
768
769 if (reg->type == NOT_INIT) {
770 verbose("R%d !read_ok\n", regno);
771 return -EACCES;
772 }
773
774 if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
775 arg_type == ARG_PTR_TO_MAP_VALUE) {
776 expected_type = PTR_TO_STACK;
777 } else if (arg_type == ARG_CONST_STACK_SIZE) {
778 expected_type = CONST_IMM;
779 } else if (arg_type == ARG_CONST_MAP_PTR) {
780 expected_type = CONST_PTR_TO_MAP;
781 } else {
782 verbose("unsupported arg_type %d\n", arg_type);
783 return -EFAULT;
784 }
785
786 if (reg->type != expected_type) {
787 verbose("R%d type=%s expected=%s\n", regno,
788 reg_type_str[reg->type], reg_type_str[expected_type]);
789 return -EACCES;
790 }
791
792 if (arg_type == ARG_CONST_MAP_PTR) {
793 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
794 *mapp = reg->map_ptr;
795
796 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
797 /* bpf_map_xxx(..., map_ptr, ..., key) call:
798 * check that [key, key + map->key_size) are within
799 * stack limits and initialized
800 */
801 if (!*mapp) {
802 /* in function declaration map_ptr must come before
803 * map_key, so that it's verified and known before
804 * we have to check map_key here. Otherwise it means
805 * that kernel subsystem misconfigured verifier
806 */
807 verbose("invalid map_ptr to access map->key\n");
808 return -EACCES;
809 }
810 err = check_stack_boundary(env, regno, (*mapp)->key_size);
811
812 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
813 /* bpf_map_xxx(..., map_ptr, ..., value) call:
814 * check [value, value + map->value_size) validity
815 */
816 if (!*mapp) {
817 /* kernel subsystem misconfigured verifier */
818 verbose("invalid map_ptr to access map->value\n");
819 return -EACCES;
820 }
821 err = check_stack_boundary(env, regno, (*mapp)->value_size);
822
823 } else if (arg_type == ARG_CONST_STACK_SIZE) {
824 /* bpf_xxx(..., buf, len) call will access 'len' bytes
825 * from stack pointer 'buf'. Check it
826 * note: regno == len, regno - 1 == buf
827 */
828 if (regno == 0) {
829 /* kernel subsystem misconfigured verifier */
830 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
831 return -EACCES;
832 }
833 err = check_stack_boundary(env, regno - 1, reg->imm);
834 }
835
836 return err;
837}
838
839static int check_call(struct verifier_env *env, int func_id)
840{
841 struct verifier_state *state = &env->cur_state;
842 const struct bpf_func_proto *fn = NULL;
843 struct reg_state *regs = state->regs;
844 struct bpf_map *map = NULL;
845 struct reg_state *reg;
846 int i, err;
847
848 /* find function prototype */
849 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
850 verbose("invalid func %d\n", func_id);
851 return -EINVAL;
852 }
853
854 if (env->prog->aux->ops->get_func_proto)
855 fn = env->prog->aux->ops->get_func_proto(func_id);
856
857 if (!fn) {
858 verbose("unknown func %d\n", func_id);
859 return -EINVAL;
860 }
861
862 /* eBPF programs must be GPL compatible to use GPL-ed functions */
863 if (!env->prog->aux->is_gpl_compatible && fn->gpl_only) {
864 verbose("cannot call GPL only function from proprietary program\n");
865 return -EINVAL;
866 }
867
868 /* check args */
869 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map);
870 if (err)
871 return err;
872 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map);
873 if (err)
874 return err;
875 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map);
876 if (err)
877 return err;
878 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map);
879 if (err)
880 return err;
881 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map);
882 if (err)
883 return err;
884
885 /* reset caller saved regs */
886 for (i = 0; i < CALLER_SAVED_REGS; i++) {
887 reg = regs + caller_saved[i];
888 reg->type = NOT_INIT;
889 reg->imm = 0;
890 }
891
892 /* update return register */
893 if (fn->ret_type == RET_INTEGER) {
894 regs[BPF_REG_0].type = UNKNOWN_VALUE;
895 } else if (fn->ret_type == RET_VOID) {
896 regs[BPF_REG_0].type = NOT_INIT;
897 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
898 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
899 /* remember map_ptr, so that check_map_access()
900 * can check 'value_size' boundary of memory access
901 * to map element returned from bpf_map_lookup_elem()
902 */
903 if (map == NULL) {
904 verbose("kernel subsystem misconfigured verifier\n");
905 return -EINVAL;
906 }
907 regs[BPF_REG_0].map_ptr = map;
908 } else {
909 verbose("unknown return type %d of func %d\n",
910 fn->ret_type, func_id);
911 return -EINVAL;
912 }
913 return 0;
914}
915
916/* check validity of 32-bit and 64-bit arithmetic operations */
917static int check_alu_op(struct reg_state *regs, struct bpf_insn *insn)
918{
919 u8 opcode = BPF_OP(insn->code);
920 int err;
921
922 if (opcode == BPF_END || opcode == BPF_NEG) {
923 if (opcode == BPF_NEG) {
924 if (BPF_SRC(insn->code) != 0 ||
925 insn->src_reg != BPF_REG_0 ||
926 insn->off != 0 || insn->imm != 0) {
927 verbose("BPF_NEG uses reserved fields\n");
928 return -EINVAL;
929 }
930 } else {
931 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
932 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
933 verbose("BPF_END uses reserved fields\n");
934 return -EINVAL;
935 }
936 }
937
938 /* check src operand */
939 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
940 if (err)
941 return err;
942
943 /* check dest operand */
944 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
945 if (err)
946 return err;
947
948 } else if (opcode == BPF_MOV) {
949
950 if (BPF_SRC(insn->code) == BPF_X) {
951 if (insn->imm != 0 || insn->off != 0) {
952 verbose("BPF_MOV uses reserved fields\n");
953 return -EINVAL;
954 }
955
956 /* check src operand */
957 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
958 if (err)
959 return err;
960 } else {
961 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
962 verbose("BPF_MOV uses reserved fields\n");
963 return -EINVAL;
964 }
965 }
966
967 /* check dest operand */
968 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
969 if (err)
970 return err;
971
972 if (BPF_SRC(insn->code) == BPF_X) {
973 if (BPF_CLASS(insn->code) == BPF_ALU64) {
974 /* case: R1 = R2
975 * copy register state to dest reg
976 */
977 regs[insn->dst_reg] = regs[insn->src_reg];
978 } else {
979 regs[insn->dst_reg].type = UNKNOWN_VALUE;
980 regs[insn->dst_reg].map_ptr = NULL;
981 }
982 } else {
983 /* case: R = imm
984 * remember the value we stored into this reg
985 */
986 regs[insn->dst_reg].type = CONST_IMM;
987 regs[insn->dst_reg].imm = insn->imm;
988 }
989
990 } else if (opcode > BPF_END) {
991 verbose("invalid BPF_ALU opcode %x\n", opcode);
992 return -EINVAL;
993
994 } else { /* all other ALU ops: and, sub, xor, add, ... */
995
996 bool stack_relative = false;
997
998 if (BPF_SRC(insn->code) == BPF_X) {
999 if (insn->imm != 0 || insn->off != 0) {
1000 verbose("BPF_ALU uses reserved fields\n");
1001 return -EINVAL;
1002 }
1003 /* check src1 operand */
1004 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1005 if (err)
1006 return err;
1007 } else {
1008 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1009 verbose("BPF_ALU uses reserved fields\n");
1010 return -EINVAL;
1011 }
1012 }
1013
1014 /* check src2 operand */
1015 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1016 if (err)
1017 return err;
1018
1019 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1020 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1021 verbose("div by zero\n");
1022 return -EINVAL;
1023 }
1024
1025 /* pattern match 'bpf_add Rx, imm' instruction */
1026 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1027 regs[insn->dst_reg].type == FRAME_PTR &&
1028 BPF_SRC(insn->code) == BPF_K)
1029 stack_relative = true;
1030
1031 /* check dest operand */
1032 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1033 if (err)
1034 return err;
1035
1036 if (stack_relative) {
1037 regs[insn->dst_reg].type = PTR_TO_STACK;
1038 regs[insn->dst_reg].imm = insn->imm;
1039 }
1040 }
1041
1042 return 0;
1043}
1044
1045static int check_cond_jmp_op(struct verifier_env *env,
1046 struct bpf_insn *insn, int *insn_idx)
1047{
1048 struct reg_state *regs = env->cur_state.regs;
1049 struct verifier_state *other_branch;
1050 u8 opcode = BPF_OP(insn->code);
1051 int err;
1052
1053 if (opcode > BPF_EXIT) {
1054 verbose("invalid BPF_JMP opcode %x\n", opcode);
1055 return -EINVAL;
1056 }
1057
1058 if (BPF_SRC(insn->code) == BPF_X) {
1059 if (insn->imm != 0) {
1060 verbose("BPF_JMP uses reserved fields\n");
1061 return -EINVAL;
1062 }
1063
1064 /* check src1 operand */
1065 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1066 if (err)
1067 return err;
1068 } else {
1069 if (insn->src_reg != BPF_REG_0) {
1070 verbose("BPF_JMP uses reserved fields\n");
1071 return -EINVAL;
1072 }
1073 }
1074
1075 /* check src2 operand */
1076 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1077 if (err)
1078 return err;
1079
1080 /* detect if R == 0 where R was initialized to zero earlier */
1081 if (BPF_SRC(insn->code) == BPF_K &&
1082 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1083 regs[insn->dst_reg].type == CONST_IMM &&
1084 regs[insn->dst_reg].imm == insn->imm) {
1085 if (opcode == BPF_JEQ) {
1086 /* if (imm == imm) goto pc+off;
1087 * only follow the goto, ignore fall-through
1088 */
1089 *insn_idx += insn->off;
1090 return 0;
1091 } else {
1092 /* if (imm != imm) goto pc+off;
1093 * only follow fall-through branch, since
1094 * that's where the program will go
1095 */
1096 return 0;
1097 }
1098 }
1099
1100 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1101 if (!other_branch)
1102 return -EFAULT;
1103
1104 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1105 if (BPF_SRC(insn->code) == BPF_K &&
1106 insn->imm == 0 && (opcode == BPF_JEQ ||
1107 opcode == BPF_JNE) &&
1108 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1109 if (opcode == BPF_JEQ) {
1110 /* next fallthrough insn can access memory via
1111 * this register
1112 */
1113 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1114 /* branch targer cannot access it, since reg == 0 */
1115 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1116 other_branch->regs[insn->dst_reg].imm = 0;
1117 } else {
1118 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1119 regs[insn->dst_reg].type = CONST_IMM;
1120 regs[insn->dst_reg].imm = 0;
1121 }
1122 } else if (BPF_SRC(insn->code) == BPF_K &&
1123 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1124
1125 if (opcode == BPF_JEQ) {
1126 /* detect if (R == imm) goto
1127 * and in the target state recognize that R = imm
1128 */
1129 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1130 other_branch->regs[insn->dst_reg].imm = insn->imm;
1131 } else {
1132 /* detect if (R != imm) goto
1133 * and in the fall-through state recognize that R = imm
1134 */
1135 regs[insn->dst_reg].type = CONST_IMM;
1136 regs[insn->dst_reg].imm = insn->imm;
1137 }
1138 }
1139 if (log_level)
1140 print_verifier_state(env);
1141 return 0;
1142}
1143
0246e64d
AS		 1144/* return the map pointer stored inside BPF_LD_IMM64 instruction */
1145static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1146{
1147 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1148
1149 return (struct bpf_map *) (unsigned long) imm64;
1150}
1151
17a52670
AS		 1152/* verify BPF_LD_IMM64 instruction */
1153static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1154{
1155 struct reg_state *regs = env->cur_state.regs;
1156 int err;
1157
1158 if (BPF_SIZE(insn->code) != BPF_DW) {
1159 verbose("invalid BPF_LD_IMM insn\n");
1160 return -EINVAL;
1161 }
1162 if (insn->off != 0) {
1163 verbose("BPF_LD_IMM64 uses reserved fields\n");
1164 return -EINVAL;
1165 }
1166
1167 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1168 if (err)
1169 return err;
1170
1171 if (insn->src_reg == 0)
1172 /* generic move 64-bit immediate into a register */
1173 return 0;
1174
1175 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1176 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1177
1178 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1179 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1180 return 0;
1181}
1182
475fb78f
AS		 1183/* non-recursive DFS pseudo code
1184 * 1 procedure DFS-iterative(G,v):
1185 * 2 label v as discovered
1186 * 3 let S be a stack
1187 * 4 S.push(v)
1188 * 5 while S is not empty
1189 * 6 t <- S.pop()
1190 * 7 if t is what we're looking for:
1191 * 8 return t
1192 * 9 for all edges e in G.adjacentEdges(t) do
1193 * 10 if edge e is already labelled
1194 * 11 continue with the next edge
1195 * 12 w <- G.adjacentVertex(t,e)
1196 * 13 if vertex w is not discovered and not explored
1197 * 14 label e as tree-edge
1198 * 15 label w as discovered
1199 * 16 S.push(w)
1200 * 17 continue at 5
1201 * 18 else if vertex w is discovered
1202 * 19 label e as back-edge
1203 * 20 else
1204 * 21 // vertex w is explored
1205 * 22 label e as forward- or cross-edge
1206 * 23 label t as explored
1207 * 24 S.pop()
1208 *
1209 * convention:
1210 * 0x10 - discovered
1211 * 0x11 - discovered and fall-through edge labelled
1212 * 0x12 - discovered and fall-through and branch edges labelled
1213 * 0x20 - explored
1214 */
1215
1216enum {
1217 DISCOVERED = 0x10,
1218 EXPLORED = 0x20,
1219 FALLTHROUGH = 1,
1220 BRANCH = 2,
1221};
1222
f1bca824
AS		 1223#define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1224
475fb78f
AS		 1225static int *insn_stack; /* stack of insns to process */
1226static int cur_stack; /* current stack index */
1227static int *insn_state;
1228
1229/* t, w, e - match pseudo-code above:
1230 * t - index of current instruction
1231 * w - next instruction
1232 * e - edge
1233 */
1234static int push_insn(int t, int w, int e, struct verifier_env *env)
1235{
1236 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1237 return 0;
1238
1239 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1240 return 0;
1241
1242 if (w < 0 || w >= env->prog->len) {
1243 verbose("jump out of range from insn %d to %d\n", t, w);
1244 return -EINVAL;
1245 }
1246
f1bca824
AS		 1247 if (e == BRANCH)
1248 /* mark branch target for state pruning */
1249 env->explored_states[w] = STATE_LIST_MARK;
1250
475fb78f
AS		 1251 if (insn_state[w] == 0) {
1252 /* tree-edge */
1253 insn_state[t] = DISCOVERED | e;
1254 insn_state[w] = DISCOVERED;
1255 if (cur_stack >= env->prog->len)
1256 return -E2BIG;
1257 insn_stack[cur_stack++] = w;
1258 return 1;
1259 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1260 verbose("back-edge from insn %d to %d\n", t, w);
1261 return -EINVAL;
1262 } else if (insn_state[w] == EXPLORED) {
1263 /* forward- or cross-edge */
1264 insn_state[t] = DISCOVERED | e;
1265 } else {
1266 verbose("insn state internal bug\n");
1267 return -EFAULT;
1268 }
1269 return 0;
1270}
1271
1272/* non-recursive depth-first-search to detect loops in BPF program
1273 * loop == back-edge in directed graph
1274 */
1275static int check_cfg(struct verifier_env *env)
1276{
1277 struct bpf_insn *insns = env->prog->insnsi;
1278 int insn_cnt = env->prog->len;
1279 int ret = 0;
1280 int i, t;
1281
1282 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1283 if (!insn_state)
1284 return -ENOMEM;
1285
1286 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1287 if (!insn_stack) {
1288 kfree(insn_state);
1289 return -ENOMEM;
1290 }
1291
1292 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1293 insn_stack[0] = 0; /* 0 is the first instruction */
1294 cur_stack = 1;
1295
1296peek_stack:
1297 if (cur_stack == 0)
1298 goto check_state;
1299 t = insn_stack[cur_stack - 1];
1300
1301 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1302 u8 opcode = BPF_OP(insns[t].code);
1303
1304 if (opcode == BPF_EXIT) {
1305 goto mark_explored;
1306 } else if (opcode == BPF_CALL) {
1307 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1308 if (ret == 1)
1309 goto peek_stack;
1310 else if (ret < 0)
1311 goto err_free;
1312 } else if (opcode == BPF_JA) {
1313 if (BPF_SRC(insns[t].code) != BPF_K) {
1314 ret = -EINVAL;
1315 goto err_free;
1316 }
1317 /* unconditional jump with single edge */
1318 ret = push_insn(t, t + insns[t].off + 1,
1319 FALLTHROUGH, env);
1320 if (ret == 1)
1321 goto peek_stack;
1322 else if (ret < 0)
1323 goto err_free;
f1bca824
AS		 1324 /* tell verifier to check for equivalent states
1325 * after every call and jump
1326 */
1327 env->explored_states[t + 1] = STATE_LIST_MARK;
475fb78f
AS		 1328 } else {
1329 /* conditional jump with two edges */
1330 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1331 if (ret == 1)
1332 goto peek_stack;
1333 else if (ret < 0)
1334 goto err_free;
1335
1336 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1337 if (ret == 1)
1338 goto peek_stack;
1339 else if (ret < 0)
1340 goto err_free;
1341 }
1342 } else {
1343 /* all other non-branch instructions with single
1344 * fall-through edge
1345 */
1346 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1347 if (ret == 1)
1348 goto peek_stack;
1349 else if (ret < 0)
1350 goto err_free;
1351 }
1352
1353mark_explored:
1354 insn_state[t] = EXPLORED;
1355 if (cur_stack-- <= 0) {
1356 verbose("pop stack internal bug\n");
1357 ret = -EFAULT;
1358 goto err_free;
1359 }
1360 goto peek_stack;
1361
1362check_state:
1363 for (i = 0; i < insn_cnt; i++) {
1364 if (insn_state[i] != EXPLORED) {
1365 verbose("unreachable insn %d\n", i);
1366 ret = -EINVAL;
1367 goto err_free;
1368 }
1369 }
1370 ret = 0; /* cfg looks good */
1371
1372err_free:
1373 kfree(insn_state);
1374 kfree(insn_stack);
1375 return ret;
1376}
1377
f1bca824
AS		 1378/* compare two verifier states
1379 *
1380 * all states stored in state_list are known to be valid, since
1381 * verifier reached 'bpf_exit' instruction through them
1382 *
1383 * this function is called when verifier exploring different branches of
1384 * execution popped from the state stack. If it sees an old state that has
1385 * more strict register state and more strict stack state then this execution
1386 * branch doesn't need to be explored further, since verifier already
1387 * concluded that more strict state leads to valid finish.
1388 *
1389 * Therefore two states are equivalent if register state is more conservative
1390 * and explored stack state is more conservative than the current one.
1391 * Example:
1392 * explored current
1393 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1394 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1395 *
1396 * In other words if current stack state (one being explored) has more
1397 * valid slots than old one that already passed validation, it means
1398 * the verifier can stop exploring and conclude that current state is valid too
1399 *
1400 * Similarly with registers. If explored state has register type as invalid
1401 * whereas register type in current state is meaningful, it means that
1402 * the current state will reach 'bpf_exit' instruction safely
1403 */
1404static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1405{
1406 int i;
1407
1408 for (i = 0; i < MAX_BPF_REG; i++) {
1409 if (memcmp(&old->regs[i], &cur->regs[i],
1410 sizeof(old->regs[0])) != 0) {
1411 if (old->regs[i].type == NOT_INIT ||
32bf08a6
AS		 1412 (old->regs[i].type == UNKNOWN_VALUE &&
1413 cur->regs[i].type != NOT_INIT))
f1bca824
AS		 1414 continue;
1415 return false;
1416 }
1417 }
1418
1419 for (i = 0; i < MAX_BPF_STACK; i++) {
1420 if (memcmp(&old->stack[i], &cur->stack[i],
1421 sizeof(old->stack[0])) != 0) {
1422 if (old->stack[i].stype == STACK_INVALID)
1423 continue;
1424 return false;
1425 }
1426 }
1427 return true;
1428}
1429
1430static int is_state_visited(struct verifier_env *env, int insn_idx)
1431{
1432 struct verifier_state_list *new_sl;
1433 struct verifier_state_list *sl;
1434
1435 sl = env->explored_states[insn_idx];
1436 if (!sl)
1437 /* this 'insn_idx' instruction wasn't marked, so we will not
1438 * be doing state search here
1439 */
1440 return 0;
1441
1442 while (sl != STATE_LIST_MARK) {
1443 if (states_equal(&sl->state, &env->cur_state))
1444 /* reached equivalent register/stack state,
1445 * prune the search
1446 */
1447 return 1;
1448 sl = sl->next;
1449 }
1450
1451 /* there were no equivalent states, remember current one.
1452 * technically the current state is not proven to be safe yet,
1453 * but it will either reach bpf_exit (which means it's safe) or
1454 * it will be rejected. Since there are no loops, we won't be
1455 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1456 */
1457 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1458 if (!new_sl)
1459 return -ENOMEM;
1460
1461 /* add new state to the head of linked list */
1462 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1463 new_sl->next = env->explored_states[insn_idx];
1464 env->explored_states[insn_idx] = new_sl;
1465 return 0;
1466}
1467
17a52670
AS		 1468static int do_check(struct verifier_env *env)
1469{
1470 struct verifier_state *state = &env->cur_state;
1471 struct bpf_insn *insns = env->prog->insnsi;
1472 struct reg_state *regs = state->regs;
1473 int insn_cnt = env->prog->len;
1474 int insn_idx, prev_insn_idx = 0;
1475 int insn_processed = 0;
1476 bool do_print_state = false;
1477
1478 init_reg_state(regs);
1479 insn_idx = 0;
1480 for (;;) {
1481 struct bpf_insn *insn;
1482 u8 class;
1483 int err;
1484
1485 if (insn_idx >= insn_cnt) {
1486 verbose("invalid insn idx %d insn_cnt %d\n",
1487 insn_idx, insn_cnt);
1488 return -EFAULT;
1489 }
1490
1491 insn = &insns[insn_idx];
1492 class = BPF_CLASS(insn->code);
1493
1494 if (++insn_processed > 32768) {
1495 verbose("BPF program is too large. Proccessed %d insn\n",
1496 insn_processed);
1497 return -E2BIG;
1498 }
1499
f1bca824
AS		 1500 err = is_state_visited(env, insn_idx);
1501 if (err < 0)
1502 return err;
1503 if (err == 1) {
1504 /* found equivalent state, can prune the search */
1505 if (log_level) {
1506 if (do_print_state)
1507 verbose("\nfrom %d to %d: safe\n",
1508 prev_insn_idx, insn_idx);
1509 else
1510 verbose("%d: safe\n", insn_idx);
1511 }
1512 goto process_bpf_exit;
1513 }
1514
17a52670
AS		 1515 if (log_level && do_print_state) {
1516 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1517 print_verifier_state(env);
1518 do_print_state = false;
1519 }
1520
1521 if (log_level) {
1522 verbose("%d: ", insn_idx);
1523 print_bpf_insn(insn);
1524 }
1525
1526 if (class == BPF_ALU || class == BPF_ALU64) {
1527 err = check_alu_op(regs, insn);
1528 if (err)
1529 return err;
1530
1531 } else if (class == BPF_LDX) {
1532 if (BPF_MODE(insn->code) != BPF_MEM ||
1533 insn->imm != 0) {
1534 verbose("BPF_LDX uses reserved fields\n");
1535 return -EINVAL;
1536 }
1537 /* check src operand */
1538 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1539 if (err)
1540 return err;
1541
1542 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1543 if (err)
1544 return err;
1545
1546 /* check that memory (src_reg + off) is readable,
1547 * the state of dst_reg will be updated by this func
1548 */
1549 err = check_mem_access(env, insn->src_reg, insn->off,
1550 BPF_SIZE(insn->code), BPF_READ,
1551 insn->dst_reg);
1552 if (err)
1553 return err;
1554
1555 } else if (class == BPF_STX) {
1556 if (BPF_MODE(insn->code) == BPF_XADD) {
1557 err = check_xadd(env, insn);
1558 if (err)
1559 return err;
1560 insn_idx++;
1561 continue;
1562 }
1563
1564 if (BPF_MODE(insn->code) != BPF_MEM ||
1565 insn->imm != 0) {
1566 verbose("BPF_STX uses reserved fields\n");
1567 return -EINVAL;
1568 }
1569 /* check src1 operand */
1570 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1571 if (err)
1572 return err;
1573 /* check src2 operand */
1574 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1575 if (err)
1576 return err;
1577
1578 /* check that memory (dst_reg + off) is writeable */
1579 err = check_mem_access(env, insn->dst_reg, insn->off,
1580 BPF_SIZE(insn->code), BPF_WRITE,
1581 insn->src_reg);
1582 if (err)
1583 return err;
1584
1585 } else if (class == BPF_ST) {
1586 if (BPF_MODE(insn->code) != BPF_MEM ||
1587 insn->src_reg != BPF_REG_0) {
1588 verbose("BPF_ST uses reserved fields\n");
1589 return -EINVAL;
1590 }
1591 /* check src operand */
1592 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1593 if (err)
1594 return err;
1595
1596 /* check that memory (dst_reg + off) is writeable */
1597 err = check_mem_access(env, insn->dst_reg, insn->off,
1598 BPF_SIZE(insn->code), BPF_WRITE,
1599 -1);
1600 if (err)
1601 return err;
1602
1603 } else if (class == BPF_JMP) {
1604 u8 opcode = BPF_OP(insn->code);
1605
1606 if (opcode == BPF_CALL) {
1607 if (BPF_SRC(insn->code) != BPF_K ||
1608 insn->off != 0 ||
1609 insn->src_reg != BPF_REG_0 ||
1610 insn->dst_reg != BPF_REG_0) {
1611 verbose("BPF_CALL uses reserved fields\n");
1612 return -EINVAL;
1613 }
1614
1615 err = check_call(env, insn->imm);
1616 if (err)
1617 return err;
1618
1619 } else if (opcode == BPF_JA) {
1620 if (BPF_SRC(insn->code) != BPF_K ||
1621 insn->imm != 0 ||
1622 insn->src_reg != BPF_REG_0 ||
1623 insn->dst_reg != BPF_REG_0) {
1624 verbose("BPF_JA uses reserved fields\n");
1625 return -EINVAL;
1626 }
1627
1628 insn_idx += insn->off + 1;
1629 continue;
1630
1631 } else if (opcode == BPF_EXIT) {
1632 if (BPF_SRC(insn->code) != BPF_K ||
1633 insn->imm != 0 ||
1634 insn->src_reg != BPF_REG_0 ||
1635 insn->dst_reg != BPF_REG_0) {
1636 verbose("BPF_EXIT uses reserved fields\n");
1637 return -EINVAL;
1638 }
1639
1640 /* eBPF calling convetion is such that R0 is used
1641 * to return the value from eBPF program.
1642 * Make sure that it's readable at this time
1643 * of bpf_exit, which means that program wrote
1644 * something into it earlier
1645 */
1646 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1647 if (err)
1648 return err;
1649
f1bca824 1650process_bpf_exit:
17a52670
AS		 1651 insn_idx = pop_stack(env, &prev_insn_idx);
1652 if (insn_idx < 0) {
1653 break;
1654 } else {
1655 do_print_state = true;
1656 continue;
1657 }
1658 } else {
1659 err = check_cond_jmp_op(env, insn, &insn_idx);
1660 if (err)
1661 return err;
1662 }
1663 } else if (class == BPF_LD) {
1664 u8 mode = BPF_MODE(insn->code);
1665
1666 if (mode == BPF_ABS || mode == BPF_IND) {
1667 verbose("LD_ABS is not supported yet\n");
1668 return -EINVAL;
1669 } else if (mode == BPF_IMM) {
1670 err = check_ld_imm(env, insn);
1671 if (err)
1672 return err;
1673
1674 insn_idx++;
1675 } else {
1676 verbose("invalid BPF_LD mode\n");
1677 return -EINVAL;
1678 }
1679 } else {
1680 verbose("unknown insn class %d\n", class);
1681 return -EINVAL;
1682 }
1683
1684 insn_idx++;
1685 }
1686
1687 return 0;
1688}
1689
0246e64d
AS		 1690/* look for pseudo eBPF instructions that access map FDs and
1691 * replace them with actual map pointers
1692 */
1693static int replace_map_fd_with_map_ptr(struct verifier_env *env)
1694{
1695 struct bpf_insn *insn = env->prog->insnsi;
1696 int insn_cnt = env->prog->len;
1697 int i, j;
1698
1699 for (i = 0; i < insn_cnt; i++, insn++) {
1700 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
1701 struct bpf_map *map;
1702 struct fd f;
1703
1704 if (i == insn_cnt - 1 || insn[1].code != 0 ||
1705 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
1706 insn[1].off != 0) {
1707 verbose("invalid bpf_ld_imm64 insn\n");
1708 return -EINVAL;
1709 }
1710
1711 if (insn->src_reg == 0)
1712 /* valid generic load 64-bit imm */
1713 goto next_insn;
1714
1715 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
1716 verbose("unrecognized bpf_ld_imm64 insn\n");
1717 return -EINVAL;
1718 }
1719
1720 f = fdget(insn->imm);
1721
1722 map = bpf_map_get(f);
1723 if (IS_ERR(map)) {
1724 verbose("fd %d is not pointing to valid bpf_map\n",
1725 insn->imm);
1726 fdput(f);
1727 return PTR_ERR(map);
1728 }
1729
1730 /* store map pointer inside BPF_LD_IMM64 instruction */
1731 insn[0].imm = (u32) (unsigned long) map;
1732 insn[1].imm = ((u64) (unsigned long) map) >> 32;
1733
1734 /* check whether we recorded this map already */
1735 for (j = 0; j < env->used_map_cnt; j++)
1736 if (env->used_maps[j] == map) {
1737 fdput(f);
1738 goto next_insn;
1739 }
1740
1741 if (env->used_map_cnt >= MAX_USED_MAPS) {
1742 fdput(f);
1743 return -E2BIG;
1744 }
1745
1746 /* remember this map */
1747 env->used_maps[env->used_map_cnt++] = map;
1748
1749 /* hold the map. If the program is rejected by verifier,
1750 * the map will be released by release_maps() or it
1751 * will be used by the valid program until it's unloaded
1752 * and all maps are released in free_bpf_prog_info()
1753 */
1754 atomic_inc(&map->refcnt);
1755
1756 fdput(f);
1757next_insn:
1758 insn++;
1759 i++;
1760 }
1761 }
1762
1763 /* now all pseudo BPF_LD_IMM64 instructions load valid
1764 * 'struct bpf_map *' into a register instead of user map_fd.
1765 * These pointers will be used later by verifier to validate map access.
1766 */
1767 return 0;
1768}
1769
1770/* drop refcnt of maps used by the rejected program */
1771static void release_maps(struct verifier_env *env)
1772{
1773 int i;
1774
1775 for (i = 0; i < env->used_map_cnt; i++)
1776 bpf_map_put(env->used_maps[i]);
1777}
1778
1779/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
1780static void convert_pseudo_ld_imm64(struct verifier_env *env)
1781{
1782 struct bpf_insn *insn = env->prog->insnsi;
1783 int insn_cnt = env->prog->len;
1784 int i;
1785
1786 for (i = 0; i < insn_cnt; i++, insn++)
1787 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
1788 insn->src_reg = 0;
1789}
1790
f1bca824
AS		 1791static void free_states(struct verifier_env *env)
1792{
1793 struct verifier_state_list *sl, *sln;
1794 int i;
1795
1796 if (!env->explored_states)
1797 return;
1798
1799 for (i = 0; i < env->prog->len; i++) {
1800 sl = env->explored_states[i];
1801
1802 if (sl)
1803 while (sl != STATE_LIST_MARK) {
1804 sln = sl->next;
1805 kfree(sl);
1806 sl = sln;
1807 }
1808 }
1809
1810 kfree(env->explored_states);
1811}
1812
51580e79
AS		 1813int bpf_check(struct bpf_prog *prog, union bpf_attr *attr)
1814{
cbd35700
AS		 1815 char __user *log_ubuf = NULL;
1816 struct verifier_env *env;
51580e79
AS		 1817 int ret = -EINVAL;
1818
cbd35700
AS		 1819 if (prog->len <= 0 || prog->len > BPF_MAXINSNS)
1820 return -E2BIG;
1821
1822 /* 'struct verifier_env' can be global, but since it's not small,
1823 * allocate/free it every time bpf_check() is called
1824 */
1825 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
1826 if (!env)
1827 return -ENOMEM;
1828
0246e64d
AS		 1829 env->prog = prog;
1830
cbd35700
AS		 1831 /* grab the mutex to protect few globals used by verifier */
1832 mutex_lock(&bpf_verifier_lock);
1833
1834 if (attr->log_level || attr->log_buf || attr->log_size) {
1835 /* user requested verbose verifier output
1836 * and supplied buffer to store the verification trace
1837 */
1838 log_level = attr->log_level;
1839 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
1840 log_size = attr->log_size;
1841 log_len = 0;
1842
1843 ret = -EINVAL;
1844 /* log_* values have to be sane */
1845 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
1846 log_level == 0 || log_ubuf == NULL)
1847 goto free_env;
1848
1849 ret = -ENOMEM;
1850 log_buf = vmalloc(log_size);
1851 if (!log_buf)
1852 goto free_env;
1853 } else {
1854 log_level = 0;
1855 }
1856
0246e64d
AS		 1857 ret = replace_map_fd_with_map_ptr(env);
1858 if (ret < 0)
1859 goto skip_full_check;
1860
f1bca824
AS		 1861 env->explored_states = kcalloc(prog->len,
1862 sizeof(struct verifier_state_list *),
1863 GFP_USER);
1864 ret = -ENOMEM;
1865 if (!env->explored_states)
1866 goto skip_full_check;
1867
475fb78f
AS		 1868 ret = check_cfg(env);
1869 if (ret < 0)
1870 goto skip_full_check;
1871
17a52670 1872 ret = do_check(env);
cbd35700 1873
0246e64d 1874skip_full_check:
17a52670 1875 while (pop_stack(env, NULL) >= 0);
f1bca824 1876 free_states(env);
0246e64d 1877
cbd35700
AS		 1878 if (log_level && log_len >= log_size - 1) {
1879 BUG_ON(log_len >= log_size);
1880 /* verifier log exceeded user supplied buffer */
1881 ret = -ENOSPC;
1882 /* fall through to return what was recorded */
1883 }
1884
1885 /* copy verifier log back to user space including trailing zero */
1886 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
1887 ret = -EFAULT;
1888 goto free_log_buf;
1889 }
1890
0246e64d
AS		 1891 if (ret == 0 && env->used_map_cnt) {
1892 /* if program passed verifier, update used_maps in bpf_prog_info */
1893 prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
1894 sizeof(env->used_maps[0]),
1895 GFP_KERNEL);
1896
1897 if (!prog->aux->used_maps) {
1898 ret = -ENOMEM;
1899 goto free_log_buf;
1900 }
1901
1902 memcpy(prog->aux->used_maps, env->used_maps,
1903 sizeof(env->used_maps[0]) * env->used_map_cnt);
1904 prog->aux->used_map_cnt = env->used_map_cnt;
1905
1906 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
1907 * bpf_ld_imm64 instructions
1908 */
1909 convert_pseudo_ld_imm64(env);
1910 }
cbd35700
AS		 1911
1912free_log_buf:
1913 if (log_level)
1914 vfree(log_buf);
1915free_env:
0246e64d
AS		 1916 if (!prog->aux->used_maps)
1917 /* if we didn't copy map pointers into bpf_prog_info, release
1918 * them now. Otherwise free_bpf_prog_info() will release them.
1919 */
1920 release_maps(env);
cbd35700
AS		 1921 kfree(env);
1922 mutex_unlock(&bpf_verifier_lock);
51580e79
AS		 1923 return ret;
1924}
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