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Restartable sequences: tests: introduce simple rseq start/finish
[deliverable/linux.git] / kernel / bpf / verifier.c
1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 * Copyright (c) 2016 Facebook
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of version 2 of the GNU General Public
6 * License as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
12 */
13 #include <linux/kernel.h>
14 #include <linux/types.h>
15 #include <linux/slab.h>
16 #include <linux/bpf.h>
17 #include <linux/filter.h>
18 #include <net/netlink.h>
19 #include <linux/file.h>
20 #include <linux/vmalloc.h>
21
22 /* bpf_check() is a static code analyzer that walks eBPF program
23 * instruction by instruction and updates register/stack state.
24 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
25 *
26 * The first pass is depth-first-search to check that the program is a DAG.
27 * It rejects the following programs:
28 * - larger than BPF_MAXINSNS insns
29 * - if loop is present (detected via back-edge)
30 * - unreachable insns exist (shouldn't be a forest. program = one function)
31 * - out of bounds or malformed jumps
32 * The second pass is all possible path descent from the 1st insn.
33 * Since it's analyzing all pathes through the program, the length of the
34 * analysis is limited to 32k insn, which may be hit even if total number of
35 * insn is less then 4K, but there are too many branches that change stack/regs.
36 * Number of 'branches to be analyzed' is limited to 1k
37 *
38 * On entry to each instruction, each register has a type, and the instruction
39 * changes the types of the registers depending on instruction semantics.
40 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
41 * copied to R1.
42 *
43 * All registers are 64-bit.
44 * R0 - return register
45 * R1-R5 argument passing registers
46 * R6-R9 callee saved registers
47 * R10 - frame pointer read-only
48 *
49 * At the start of BPF program the register R1 contains a pointer to bpf_context
50 * and has type PTR_TO_CTX.
51 *
52 * Verifier tracks arithmetic operations on pointers in case:
53 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
54 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
55 * 1st insn copies R10 (which has FRAME_PTR) type into R1
56 * and 2nd arithmetic instruction is pattern matched to recognize
57 * that it wants to construct a pointer to some element within stack.
58 * So after 2nd insn, the register R1 has type PTR_TO_STACK
59 * (and -20 constant is saved for further stack bounds checking).
60 * Meaning that this reg is a pointer to stack plus known immediate constant.
61 *
62 * Most of the time the registers have UNKNOWN_VALUE type, which
63 * means the register has some value, but it's not a valid pointer.
64 * (like pointer plus pointer becomes UNKNOWN_VALUE type)
65 *
66 * When verifier sees load or store instructions the type of base register
67 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
68 * types recognized by check_mem_access() function.
69 *
70 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
71 * and the range of [ptr, ptr + map's value_size) is accessible.
72 *
73 * registers used to pass values to function calls are checked against
74 * function argument constraints.
75 *
76 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
77 * It means that the register type passed to this function must be
78 * PTR_TO_STACK and it will be used inside the function as
79 * 'pointer to map element key'
80 *
81 * For example the argument constraints for bpf_map_lookup_elem():
82 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
83 * .arg1_type = ARG_CONST_MAP_PTR,
84 * .arg2_type = ARG_PTR_TO_MAP_KEY,
85 *
86 * ret_type says that this function returns 'pointer to map elem value or null'
87 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
88 * 2nd argument should be a pointer to stack, which will be used inside
89 * the helper function as a pointer to map element key.
90 *
91 * On the kernel side the helper function looks like:
92 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
93 * {
94 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
95 * void *key = (void *) (unsigned long) r2;
96 * void *value;
97 *
98 * here kernel can access 'key' and 'map' pointers safely, knowing that
99 * [key, key + map->key_size) bytes are valid and were initialized on
100 * the stack of eBPF program.
101 * }
102 *
103 * Corresponding eBPF program may look like:
104 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
105 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
106 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
107 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
108 * here verifier looks at prototype of map_lookup_elem() and sees:
109 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
110 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
111 *
112 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
113 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
114 * and were initialized prior to this call.
115 * If it's ok, then verifier allows this BPF_CALL insn and looks at
116 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
117 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
118 * returns ether pointer to map value or NULL.
119 *
120 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
121 * insn, the register holding that pointer in the true branch changes state to
122 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
123 * branch. See check_cond_jmp_op().
124 *
125 * After the call R0 is set to return type of the function and registers R1-R5
126 * are set to NOT_INIT to indicate that they are no longer readable.
127 */
128
129 struct reg_state {
130 enum bpf_reg_type type;
131 union {
132 /* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */
133 s64 imm;
134
135 /* valid when type == PTR_TO_PACKET* */
136 struct {
137 u32 id;
138 u16 off;
139 u16 range;
140 };
141
142 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
143 * PTR_TO_MAP_VALUE_OR_NULL
144 */
145 struct bpf_map *map_ptr;
146 };
147 };
148
149 enum bpf_stack_slot_type {
150 STACK_INVALID, /* nothing was stored in this stack slot */
151 STACK_SPILL, /* register spilled into stack */
152 STACK_MISC /* BPF program wrote some data into this slot */
153 };
154
155 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
156
157 /* state of the program:
158 * type of all registers and stack info
159 */
160 struct verifier_state {
161 struct reg_state regs[MAX_BPF_REG];
162 u8 stack_slot_type[MAX_BPF_STACK];
163 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
164 };
165
166 /* linked list of verifier states used to prune search */
167 struct verifier_state_list {
168 struct verifier_state state;
169 struct verifier_state_list *next;
170 };
171
172 /* verifier_state + insn_idx are pushed to stack when branch is encountered */
173 struct verifier_stack_elem {
174 /* verifer state is 'st'
175 * before processing instruction 'insn_idx'
176 * and after processing instruction 'prev_insn_idx'
177 */
178 struct verifier_state st;
179 int insn_idx;
180 int prev_insn_idx;
181 struct verifier_stack_elem *next;
182 };
183
184 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
185
186 /* single container for all structs
187 * one verifier_env per bpf_check() call
188 */
189 struct verifier_env {
190 struct bpf_prog *prog; /* eBPF program being verified */
191 struct verifier_stack_elem *head; /* stack of verifier states to be processed */
192 int stack_size; /* number of states to be processed */
193 struct verifier_state cur_state; /* current verifier state */
194 struct verifier_state_list **explored_states; /* search pruning optimization */
195 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
196 u32 used_map_cnt; /* number of used maps */
197 u32 id_gen; /* used to generate unique reg IDs */
198 bool allow_ptr_leaks;
199 };
200
201 #define BPF_COMPLEXITY_LIMIT_INSNS 65536
202 #define BPF_COMPLEXITY_LIMIT_STACK 1024
203
204 struct bpf_call_arg_meta {
205 struct bpf_map *map_ptr;
206 bool raw_mode;
207 int regno;
208 int access_size;
209 };
210
211 /* verbose verifier prints what it's seeing
212 * bpf_check() is called under lock, so no race to access these global vars
213 */
214 static u32 log_level, log_size, log_len;
215 static char *log_buf;
216
217 static DEFINE_MUTEX(bpf_verifier_lock);
218
219 /* log_level controls verbosity level of eBPF verifier.
220 * verbose() is used to dump the verification trace to the log, so the user
221 * can figure out what's wrong with the program
222 */
223 static __printf(1, 2) void verbose(const char *fmt, ...)
224 {
225 va_list args;
226
227 if (log_level == 0 || log_len >= log_size - 1)
228 return;
229
230 va_start(args, fmt);
231 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
232 va_end(args);
233 }
234
235 /* string representation of 'enum bpf_reg_type' */
236 static const char * const reg_type_str[] = {
237 [NOT_INIT] = "?",
238 [UNKNOWN_VALUE] = "inv",
239 [PTR_TO_CTX] = "ctx",
240 [CONST_PTR_TO_MAP] = "map_ptr",
241 [PTR_TO_MAP_VALUE] = "map_value",
242 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
243 [FRAME_PTR] = "fp",
244 [PTR_TO_STACK] = "fp",
245 [CONST_IMM] = "imm",
246 [PTR_TO_PACKET] = "pkt",
247 [PTR_TO_PACKET_END] = "pkt_end",
248 };
249
250 static void print_verifier_state(struct verifier_state *state)
251 {
252 struct reg_state *reg;
253 enum bpf_reg_type t;
254 int i;
255
256 for (i = 0; i < MAX_BPF_REG; i++) {
257 reg = &state->regs[i];
258 t = reg->type;
259 if (t == NOT_INIT)
260 continue;
261 verbose(" R%d=%s", i, reg_type_str[t]);
262 if (t == CONST_IMM || t == PTR_TO_STACK)
263 verbose("%lld", reg->imm);
264 else if (t == PTR_TO_PACKET)
265 verbose("(id=%d,off=%d,r=%d)",
266 reg->id, reg->off, reg->range);
267 else if (t == UNKNOWN_VALUE && reg->imm)
268 verbose("%lld", reg->imm);
269 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
270 t == PTR_TO_MAP_VALUE_OR_NULL)
271 verbose("(ks=%d,vs=%d)",
272 reg->map_ptr->key_size,
273 reg->map_ptr->value_size);
274 }
275 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
276 if (state->stack_slot_type[i] == STACK_SPILL)
277 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
278 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]);
279 }
280 verbose("\n");
281 }
282
283 static const char *const bpf_class_string[] = {
284 [BPF_LD] = "ld",
285 [BPF_LDX] = "ldx",
286 [BPF_ST] = "st",
287 [BPF_STX] = "stx",
288 [BPF_ALU] = "alu",
289 [BPF_JMP] = "jmp",
290 [BPF_RET] = "BUG",
291 [BPF_ALU64] = "alu64",
292 };
293
294 static const char *const bpf_alu_string[16] = {
295 [BPF_ADD >> 4] = "+=",
296 [BPF_SUB >> 4] = "-=",
297 [BPF_MUL >> 4] = "*=",
298 [BPF_DIV >> 4] = "/=",
299 [BPF_OR >> 4] = "|=",
300 [BPF_AND >> 4] = "&=",
301 [BPF_LSH >> 4] = "<<=",
302 [BPF_RSH >> 4] = ">>=",
303 [BPF_NEG >> 4] = "neg",
304 [BPF_MOD >> 4] = "%=",
305 [BPF_XOR >> 4] = "^=",
306 [BPF_MOV >> 4] = "=",
307 [BPF_ARSH >> 4] = "s>>=",
308 [BPF_END >> 4] = "endian",
309 };
310
311 static const char *const bpf_ldst_string[] = {
312 [BPF_W >> 3] = "u32",
313 [BPF_H >> 3] = "u16",
314 [BPF_B >> 3] = "u8",
315 [BPF_DW >> 3] = "u64",
316 };
317
318 static const char *const bpf_jmp_string[16] = {
319 [BPF_JA >> 4] = "jmp",
320 [BPF_JEQ >> 4] = "==",
321 [BPF_JGT >> 4] = ">",
322 [BPF_JGE >> 4] = ">=",
323 [BPF_JSET >> 4] = "&",
324 [BPF_JNE >> 4] = "!=",
325 [BPF_JSGT >> 4] = "s>",
326 [BPF_JSGE >> 4] = "s>=",
327 [BPF_CALL >> 4] = "call",
328 [BPF_EXIT >> 4] = "exit",
329 };
330
331 static void print_bpf_insn(struct bpf_insn *insn)
332 {
333 u8 class = BPF_CLASS(insn->code);
334
335 if (class == BPF_ALU || class == BPF_ALU64) {
336 if (BPF_SRC(insn->code) == BPF_X)
337 verbose("(%02x) %sr%d %s %sr%d\n",
338 insn->code, class == BPF_ALU ? "(u32) " : "",
339 insn->dst_reg,
340 bpf_alu_string[BPF_OP(insn->code) >> 4],
341 class == BPF_ALU ? "(u32) " : "",
342 insn->src_reg);
343 else
344 verbose("(%02x) %sr%d %s %s%d\n",
345 insn->code, class == BPF_ALU ? "(u32) " : "",
346 insn->dst_reg,
347 bpf_alu_string[BPF_OP(insn->code) >> 4],
348 class == BPF_ALU ? "(u32) " : "",
349 insn->imm);
350 } else if (class == BPF_STX) {
351 if (BPF_MODE(insn->code) == BPF_MEM)
352 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
353 insn->code,
354 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
355 insn->dst_reg,
356 insn->off, insn->src_reg);
357 else if (BPF_MODE(insn->code) == BPF_XADD)
358 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
359 insn->code,
360 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
361 insn->dst_reg, insn->off,
362 insn->src_reg);
363 else
364 verbose("BUG_%02x\n", insn->code);
365 } else if (class == BPF_ST) {
366 if (BPF_MODE(insn->code) != BPF_MEM) {
367 verbose("BUG_st_%02x\n", insn->code);
368 return;
369 }
370 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
371 insn->code,
372 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
373 insn->dst_reg,
374 insn->off, insn->imm);
375 } else if (class == BPF_LDX) {
376 if (BPF_MODE(insn->code) != BPF_MEM) {
377 verbose("BUG_ldx_%02x\n", insn->code);
378 return;
379 }
380 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
381 insn->code, insn->dst_reg,
382 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
383 insn->src_reg, insn->off);
384 } else if (class == BPF_LD) {
385 if (BPF_MODE(insn->code) == BPF_ABS) {
386 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
387 insn->code,
388 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
389 insn->imm);
390 } else if (BPF_MODE(insn->code) == BPF_IND) {
391 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
392 insn->code,
393 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
394 insn->src_reg, insn->imm);
395 } else if (BPF_MODE(insn->code) == BPF_IMM) {
396 verbose("(%02x) r%d = 0x%x\n",
397 insn->code, insn->dst_reg, insn->imm);
398 } else {
399 verbose("BUG_ld_%02x\n", insn->code);
400 return;
401 }
402 } else if (class == BPF_JMP) {
403 u8 opcode = BPF_OP(insn->code);
404
405 if (opcode == BPF_CALL) {
406 verbose("(%02x) call %d\n", insn->code, insn->imm);
407 } else if (insn->code == (BPF_JMP | BPF_JA)) {
408 verbose("(%02x) goto pc%+d\n",
409 insn->code, insn->off);
410 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
411 verbose("(%02x) exit\n", insn->code);
412 } else if (BPF_SRC(insn->code) == BPF_X) {
413 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
414 insn->code, insn->dst_reg,
415 bpf_jmp_string[BPF_OP(insn->code) >> 4],
416 insn->src_reg, insn->off);
417 } else {
418 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
419 insn->code, insn->dst_reg,
420 bpf_jmp_string[BPF_OP(insn->code) >> 4],
421 insn->imm, insn->off);
422 }
423 } else {
424 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
425 }
426 }
427
428 static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
429 {
430 struct verifier_stack_elem *elem;
431 int insn_idx;
432
433 if (env->head == NULL)
434 return -1;
435
436 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
437 insn_idx = env->head->insn_idx;
438 if (prev_insn_idx)
439 *prev_insn_idx = env->head->prev_insn_idx;
440 elem = env->head->next;
441 kfree(env->head);
442 env->head = elem;
443 env->stack_size--;
444 return insn_idx;
445 }
446
447 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
448 int prev_insn_idx)
449 {
450 struct verifier_stack_elem *elem;
451
452 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
453 if (!elem)
454 goto err;
455
456 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
457 elem->insn_idx = insn_idx;
458 elem->prev_insn_idx = prev_insn_idx;
459 elem->next = env->head;
460 env->head = elem;
461 env->stack_size++;
462 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
463 verbose("BPF program is too complex\n");
464 goto err;
465 }
466 return &elem->st;
467 err:
468 /* pop all elements and return */
469 while (pop_stack(env, NULL) >= 0);
470 return NULL;
471 }
472
473 #define CALLER_SAVED_REGS 6
474 static const int caller_saved[CALLER_SAVED_REGS] = {
475 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
476 };
477
478 static void init_reg_state(struct reg_state *regs)
479 {
480 int i;
481
482 for (i = 0; i < MAX_BPF_REG; i++) {
483 regs[i].type = NOT_INIT;
484 regs[i].imm = 0;
485 }
486
487 /* frame pointer */
488 regs[BPF_REG_FP].type = FRAME_PTR;
489
490 /* 1st arg to a function */
491 regs[BPF_REG_1].type = PTR_TO_CTX;
492 }
493
494 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
495 {
496 BUG_ON(regno >= MAX_BPF_REG);
497 regs[regno].type = UNKNOWN_VALUE;
498 regs[regno].imm = 0;
499 }
500
501 enum reg_arg_type {
502 SRC_OP, /* register is used as source operand */
503 DST_OP, /* register is used as destination operand */
504 DST_OP_NO_MARK /* same as above, check only, don't mark */
505 };
506
507 static int check_reg_arg(struct reg_state *regs, u32 regno,
508 enum reg_arg_type t)
509 {
510 if (regno >= MAX_BPF_REG) {
511 verbose("R%d is invalid\n", regno);
512 return -EINVAL;
513 }
514
515 if (t == SRC_OP) {
516 /* check whether register used as source operand can be read */
517 if (regs[regno].type == NOT_INIT) {
518 verbose("R%d !read_ok\n", regno);
519 return -EACCES;
520 }
521 } else {
522 /* check whether register used as dest operand can be written to */
523 if (regno == BPF_REG_FP) {
524 verbose("frame pointer is read only\n");
525 return -EACCES;
526 }
527 if (t == DST_OP)
528 mark_reg_unknown_value(regs, regno);
529 }
530 return 0;
531 }
532
533 static int bpf_size_to_bytes(int bpf_size)
534 {
535 if (bpf_size == BPF_W)
536 return 4;
537 else if (bpf_size == BPF_H)
538 return 2;
539 else if (bpf_size == BPF_B)
540 return 1;
541 else if (bpf_size == BPF_DW)
542 return 8;
543 else
544 return -EINVAL;
545 }
546
547 static bool is_spillable_regtype(enum bpf_reg_type type)
548 {
549 switch (type) {
550 case PTR_TO_MAP_VALUE:
551 case PTR_TO_MAP_VALUE_OR_NULL:
552 case PTR_TO_STACK:
553 case PTR_TO_CTX:
554 case PTR_TO_PACKET:
555 case PTR_TO_PACKET_END:
556 case FRAME_PTR:
557 case CONST_PTR_TO_MAP:
558 return true;
559 default:
560 return false;
561 }
562 }
563
564 /* check_stack_read/write functions track spill/fill of registers,
565 * stack boundary and alignment are checked in check_mem_access()
566 */
567 static int check_stack_write(struct verifier_state *state, int off, int size,
568 int value_regno)
569 {
570 int i;
571 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
572 * so it's aligned access and [off, off + size) are within stack limits
573 */
574
575 if (value_regno >= 0 &&
576 is_spillable_regtype(state->regs[value_regno].type)) {
577
578 /* register containing pointer is being spilled into stack */
579 if (size != BPF_REG_SIZE) {
580 verbose("invalid size of register spill\n");
581 return -EACCES;
582 }
583
584 /* save register state */
585 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
586 state->regs[value_regno];
587
588 for (i = 0; i < BPF_REG_SIZE; i++)
589 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
590 } else {
591 /* regular write of data into stack */
592 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
593 (struct reg_state) {};
594
595 for (i = 0; i < size; i++)
596 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
597 }
598 return 0;
599 }
600
601 static int check_stack_read(struct verifier_state *state, int off, int size,
602 int value_regno)
603 {
604 u8 *slot_type;
605 int i;
606
607 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
608
609 if (slot_type[0] == STACK_SPILL) {
610 if (size != BPF_REG_SIZE) {
611 verbose("invalid size of register spill\n");
612 return -EACCES;
613 }
614 for (i = 1; i < BPF_REG_SIZE; i++) {
615 if (slot_type[i] != STACK_SPILL) {
616 verbose("corrupted spill memory\n");
617 return -EACCES;
618 }
619 }
620
621 if (value_regno >= 0)
622 /* restore register state from stack */
623 state->regs[value_regno] =
624 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
625 return 0;
626 } else {
627 for (i = 0; i < size; i++) {
628 if (slot_type[i] != STACK_MISC) {
629 verbose("invalid read from stack off %d+%d size %d\n",
630 off, i, size);
631 return -EACCES;
632 }
633 }
634 if (value_regno >= 0)
635 /* have read misc data from the stack */
636 mark_reg_unknown_value(state->regs, value_regno);
637 return 0;
638 }
639 }
640
641 /* check read/write into map element returned by bpf_map_lookup_elem() */
642 static int check_map_access(struct verifier_env *env, u32 regno, int off,
643 int size)
644 {
645 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
646
647 if (off < 0 || off + size > map->value_size) {
648 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
649 map->value_size, off, size);
650 return -EACCES;
651 }
652 return 0;
653 }
654
655 #define MAX_PACKET_OFF 0xffff
656
657 static bool may_write_pkt_data(enum bpf_prog_type type)
658 {
659 switch (type) {
660 case BPF_PROG_TYPE_XDP:
661 return true;
662 default:
663 return false;
664 }
665 }
666
667 static int check_packet_access(struct verifier_env *env, u32 regno, int off,
668 int size)
669 {
670 struct reg_state *regs = env->cur_state.regs;
671 struct reg_state *reg = &regs[regno];
672
673 off += reg->off;
674 if (off < 0 || off + size > reg->range) {
675 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
676 off, size, regno, reg->id, reg->off, reg->range);
677 return -EACCES;
678 }
679 return 0;
680 }
681
682 /* check access to 'struct bpf_context' fields */
683 static int check_ctx_access(struct verifier_env *env, int off, int size,
684 enum bpf_access_type t, enum bpf_reg_type *reg_type)
685 {
686 if (env->prog->aux->ops->is_valid_access &&
687 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) {
688 /* remember the offset of last byte accessed in ctx */
689 if (env->prog->aux->max_ctx_offset < off + size)
690 env->prog->aux->max_ctx_offset = off + size;
691 return 0;
692 }
693
694 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
695 return -EACCES;
696 }
697
698 static bool is_pointer_value(struct verifier_env *env, int regno)
699 {
700 if (env->allow_ptr_leaks)
701 return false;
702
703 switch (env->cur_state.regs[regno].type) {
704 case UNKNOWN_VALUE:
705 case CONST_IMM:
706 return false;
707 default:
708 return true;
709 }
710 }
711
712 static int check_ptr_alignment(struct verifier_env *env, struct reg_state *reg,
713 int off, int size)
714 {
715 if (reg->type != PTR_TO_PACKET) {
716 if (off % size != 0) {
717 verbose("misaligned access off %d size %d\n", off, size);
718 return -EACCES;
719 } else {
720 return 0;
721 }
722 }
723
724 switch (env->prog->type) {
725 case BPF_PROG_TYPE_SCHED_CLS:
726 case BPF_PROG_TYPE_SCHED_ACT:
727 case BPF_PROG_TYPE_XDP:
728 break;
729 default:
730 verbose("verifier is misconfigured\n");
731 return -EACCES;
732 }
733
734 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
735 /* misaligned access to packet is ok on x86,arm,arm64 */
736 return 0;
737
738 if (reg->id && size != 1) {
739 verbose("Unknown packet alignment. Only byte-sized access allowed\n");
740 return -EACCES;
741 }
742
743 /* skb->data is NET_IP_ALIGN-ed */
744 if ((NET_IP_ALIGN + reg->off + off) % size != 0) {
745 verbose("misaligned packet access off %d+%d+%d size %d\n",
746 NET_IP_ALIGN, reg->off, off, size);
747 return -EACCES;
748 }
749 return 0;
750 }
751
752 /* check whether memory at (regno + off) is accessible for t = (read | write)
753 * if t==write, value_regno is a register which value is stored into memory
754 * if t==read, value_regno is a register which will receive the value from memory
755 * if t==write && value_regno==-1, some unknown value is stored into memory
756 * if t==read && value_regno==-1, don't care what we read from memory
757 */
758 static int check_mem_access(struct verifier_env *env, u32 regno, int off,
759 int bpf_size, enum bpf_access_type t,
760 int value_regno)
761 {
762 struct verifier_state *state = &env->cur_state;
763 struct reg_state *reg = &state->regs[regno];
764 int size, err = 0;
765
766 if (reg->type == PTR_TO_STACK)
767 off += reg->imm;
768
769 size = bpf_size_to_bytes(bpf_size);
770 if (size < 0)
771 return size;
772
773 err = check_ptr_alignment(env, reg, off, size);
774 if (err)
775 return err;
776
777 if (reg->type == PTR_TO_MAP_VALUE) {
778 if (t == BPF_WRITE && value_regno >= 0 &&
779 is_pointer_value(env, value_regno)) {
780 verbose("R%d leaks addr into map\n", value_regno);
781 return -EACCES;
782 }
783 err = check_map_access(env, regno, off, size);
784 if (!err && t == BPF_READ && value_regno >= 0)
785 mark_reg_unknown_value(state->regs, value_regno);
786
787 } else if (reg->type == PTR_TO_CTX) {
788 enum bpf_reg_type reg_type = UNKNOWN_VALUE;
789
790 if (t == BPF_WRITE && value_regno >= 0 &&
791 is_pointer_value(env, value_regno)) {
792 verbose("R%d leaks addr into ctx\n", value_regno);
793 return -EACCES;
794 }
795 err = check_ctx_access(env, off, size, t, &reg_type);
796 if (!err && t == BPF_READ && value_regno >= 0) {
797 mark_reg_unknown_value(state->regs, value_regno);
798 if (env->allow_ptr_leaks)
799 /* note that reg.[id|off|range] == 0 */
800 state->regs[value_regno].type = reg_type;
801 }
802
803 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {
804 if (off >= 0 || off < -MAX_BPF_STACK) {
805 verbose("invalid stack off=%d size=%d\n", off, size);
806 return -EACCES;
807 }
808 if (t == BPF_WRITE) {
809 if (!env->allow_ptr_leaks &&
810 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
811 size != BPF_REG_SIZE) {
812 verbose("attempt to corrupt spilled pointer on stack\n");
813 return -EACCES;
814 }
815 err = check_stack_write(state, off, size, value_regno);
816 } else {
817 err = check_stack_read(state, off, size, value_regno);
818 }
819 } else if (state->regs[regno].type == PTR_TO_PACKET) {
820 if (t == BPF_WRITE && !may_write_pkt_data(env->prog->type)) {
821 verbose("cannot write into packet\n");
822 return -EACCES;
823 }
824 if (t == BPF_WRITE && value_regno >= 0 &&
825 is_pointer_value(env, value_regno)) {
826 verbose("R%d leaks addr into packet\n", value_regno);
827 return -EACCES;
828 }
829 err = check_packet_access(env, regno, off, size);
830 if (!err && t == BPF_READ && value_regno >= 0)
831 mark_reg_unknown_value(state->regs, value_regno);
832 } else {
833 verbose("R%d invalid mem access '%s'\n",
834 regno, reg_type_str[reg->type]);
835 return -EACCES;
836 }
837
838 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks &&
839 state->regs[value_regno].type == UNKNOWN_VALUE) {
840 /* 1 or 2 byte load zero-extends, determine the number of
841 * zero upper bits. Not doing it fo 4 byte load, since
842 * such values cannot be added to ptr_to_packet anyway.
843 */
844 state->regs[value_regno].imm = 64 - size * 8;
845 }
846 return err;
847 }
848
849 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
850 {
851 struct reg_state *regs = env->cur_state.regs;
852 int err;
853
854 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
855 insn->imm != 0) {
856 verbose("BPF_XADD uses reserved fields\n");
857 return -EINVAL;
858 }
859
860 /* check src1 operand */
861 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
862 if (err)
863 return err;
864
865 /* check src2 operand */
866 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
867 if (err)
868 return err;
869
870 /* check whether atomic_add can read the memory */
871 err = check_mem_access(env, insn->dst_reg, insn->off,
872 BPF_SIZE(insn->code), BPF_READ, -1);
873 if (err)
874 return err;
875
876 /* check whether atomic_add can write into the same memory */
877 return check_mem_access(env, insn->dst_reg, insn->off,
878 BPF_SIZE(insn->code), BPF_WRITE, -1);
879 }
880
881 /* when register 'regno' is passed into function that will read 'access_size'
882 * bytes from that pointer, make sure that it's within stack boundary
883 * and all elements of stack are initialized
884 */
885 static int check_stack_boundary(struct verifier_env *env, int regno,
886 int access_size, bool zero_size_allowed,
887 struct bpf_call_arg_meta *meta)
888 {
889 struct verifier_state *state = &env->cur_state;
890 struct reg_state *regs = state->regs;
891 int off, i;
892
893 if (regs[regno].type != PTR_TO_STACK) {
894 if (zero_size_allowed && access_size == 0 &&
895 regs[regno].type == CONST_IMM &&
896 regs[regno].imm == 0)
897 return 0;
898
899 verbose("R%d type=%s expected=%s\n", regno,
900 reg_type_str[regs[regno].type],
901 reg_type_str[PTR_TO_STACK]);
902 return -EACCES;
903 }
904
905 off = regs[regno].imm;
906 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
907 access_size <= 0) {
908 verbose("invalid stack type R%d off=%d access_size=%d\n",
909 regno, off, access_size);
910 return -EACCES;
911 }
912
913 if (meta && meta->raw_mode) {
914 meta->access_size = access_size;
915 meta->regno = regno;
916 return 0;
917 }
918
919 for (i = 0; i < access_size; i++) {
920 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
921 verbose("invalid indirect read from stack off %d+%d size %d\n",
922 off, i, access_size);
923 return -EACCES;
924 }
925 }
926 return 0;
927 }
928
929 static int check_func_arg(struct verifier_env *env, u32 regno,
930 enum bpf_arg_type arg_type,
931 struct bpf_call_arg_meta *meta)
932 {
933 struct reg_state *reg = env->cur_state.regs + regno;
934 enum bpf_reg_type expected_type;
935 int err = 0;
936
937 if (arg_type == ARG_DONTCARE)
938 return 0;
939
940 if (reg->type == NOT_INIT) {
941 verbose("R%d !read_ok\n", regno);
942 return -EACCES;
943 }
944
945 if (arg_type == ARG_ANYTHING) {
946 if (is_pointer_value(env, regno)) {
947 verbose("R%d leaks addr into helper function\n", regno);
948 return -EACCES;
949 }
950 return 0;
951 }
952
953 if (arg_type == ARG_PTR_TO_MAP_KEY ||
954 arg_type == ARG_PTR_TO_MAP_VALUE) {
955 expected_type = PTR_TO_STACK;
956 } else if (arg_type == ARG_CONST_STACK_SIZE ||
957 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
958 expected_type = CONST_IMM;
959 } else if (arg_type == ARG_CONST_MAP_PTR) {
960 expected_type = CONST_PTR_TO_MAP;
961 } else if (arg_type == ARG_PTR_TO_CTX) {
962 expected_type = PTR_TO_CTX;
963 } else if (arg_type == ARG_PTR_TO_STACK ||
964 arg_type == ARG_PTR_TO_RAW_STACK) {
965 expected_type = PTR_TO_STACK;
966 /* One exception here. In case function allows for NULL to be
967 * passed in as argument, it's a CONST_IMM type. Final test
968 * happens during stack boundary checking.
969 */
970 if (reg->type == CONST_IMM && reg->imm == 0)
971 expected_type = CONST_IMM;
972 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK;
973 } else {
974 verbose("unsupported arg_type %d\n", arg_type);
975 return -EFAULT;
976 }
977
978 if (reg->type != expected_type) {
979 verbose("R%d type=%s expected=%s\n", regno,
980 reg_type_str[reg->type], reg_type_str[expected_type]);
981 return -EACCES;
982 }
983
984 if (arg_type == ARG_CONST_MAP_PTR) {
985 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
986 meta->map_ptr = reg->map_ptr;
987 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
988 /* bpf_map_xxx(..., map_ptr, ..., key) call:
989 * check that [key, key + map->key_size) are within
990 * stack limits and initialized
991 */
992 if (!meta->map_ptr) {
993 /* in function declaration map_ptr must come before
994 * map_key, so that it's verified and known before
995 * we have to check map_key here. Otherwise it means
996 * that kernel subsystem misconfigured verifier
997 */
998 verbose("invalid map_ptr to access map->key\n");
999 return -EACCES;
1000 }
1001 err = check_stack_boundary(env, regno, meta->map_ptr->key_size,
1002 false, NULL);
1003 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
1004 /* bpf_map_xxx(..., map_ptr, ..., value) call:
1005 * check [value, value + map->value_size) validity
1006 */
1007 if (!meta->map_ptr) {
1008 /* kernel subsystem misconfigured verifier */
1009 verbose("invalid map_ptr to access map->value\n");
1010 return -EACCES;
1011 }
1012 err = check_stack_boundary(env, regno,
1013 meta->map_ptr->value_size,
1014 false, NULL);
1015 } else if (arg_type == ARG_CONST_STACK_SIZE ||
1016 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
1017 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
1018
1019 /* bpf_xxx(..., buf, len) call will access 'len' bytes
1020 * from stack pointer 'buf'. Check it
1021 * note: regno == len, regno - 1 == buf
1022 */
1023 if (regno == 0) {
1024 /* kernel subsystem misconfigured verifier */
1025 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
1026 return -EACCES;
1027 }
1028 err = check_stack_boundary(env, regno - 1, reg->imm,
1029 zero_size_allowed, meta);
1030 }
1031
1032 return err;
1033 }
1034
1035 static int check_map_func_compatibility(struct bpf_map *map, int func_id)
1036 {
1037 if (!map)
1038 return 0;
1039
1040 /* We need a two way check, first is from map perspective ... */
1041 switch (map->map_type) {
1042 case BPF_MAP_TYPE_PROG_ARRAY:
1043 if (func_id != BPF_FUNC_tail_call)
1044 goto error;
1045 break;
1046 case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
1047 if (func_id != BPF_FUNC_perf_event_read &&
1048 func_id != BPF_FUNC_perf_event_output)
1049 goto error;
1050 break;
1051 case BPF_MAP_TYPE_STACK_TRACE:
1052 if (func_id != BPF_FUNC_get_stackid)
1053 goto error;
1054 break;
1055 case BPF_MAP_TYPE_CGROUP_ARRAY:
1056 if (func_id != BPF_FUNC_skb_under_cgroup)
1057 goto error;
1058 break;
1059 default:
1060 break;
1061 }
1062
1063 /* ... and second from the function itself. */
1064 switch (func_id) {
1065 case BPF_FUNC_tail_call:
1066 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
1067 goto error;
1068 break;
1069 case BPF_FUNC_perf_event_read:
1070 case BPF_FUNC_perf_event_output:
1071 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
1072 goto error;
1073 break;
1074 case BPF_FUNC_get_stackid:
1075 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
1076 goto error;
1077 break;
1078 case BPF_FUNC_skb_under_cgroup:
1079 if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
1080 goto error;
1081 break;
1082 default:
1083 break;
1084 }
1085
1086 return 0;
1087 error:
1088 verbose("cannot pass map_type %d into func %d\n",
1089 map->map_type, func_id);
1090 return -EINVAL;
1091 }
1092
1093 static int check_raw_mode(const struct bpf_func_proto *fn)
1094 {
1095 int count = 0;
1096
1097 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK)
1098 count++;
1099 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK)
1100 count++;
1101 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK)
1102 count++;
1103 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK)
1104 count++;
1105 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK)
1106 count++;
1107
1108 return count > 1 ? -EINVAL : 0;
1109 }
1110
1111 static void clear_all_pkt_pointers(struct verifier_env *env)
1112 {
1113 struct verifier_state *state = &env->cur_state;
1114 struct reg_state *regs = state->regs, *reg;
1115 int i;
1116
1117 for (i = 0; i < MAX_BPF_REG; i++)
1118 if (regs[i].type == PTR_TO_PACKET ||
1119 regs[i].type == PTR_TO_PACKET_END)
1120 mark_reg_unknown_value(regs, i);
1121
1122 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1123 if (state->stack_slot_type[i] != STACK_SPILL)
1124 continue;
1125 reg = &state->spilled_regs[i / BPF_REG_SIZE];
1126 if (reg->type != PTR_TO_PACKET &&
1127 reg->type != PTR_TO_PACKET_END)
1128 continue;
1129 reg->type = UNKNOWN_VALUE;
1130 reg->imm = 0;
1131 }
1132 }
1133
1134 static int check_call(struct verifier_env *env, int func_id)
1135 {
1136 struct verifier_state *state = &env->cur_state;
1137 const struct bpf_func_proto *fn = NULL;
1138 struct reg_state *regs = state->regs;
1139 struct reg_state *reg;
1140 struct bpf_call_arg_meta meta;
1141 bool changes_data;
1142 int i, err;
1143
1144 /* find function prototype */
1145 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
1146 verbose("invalid func %d\n", func_id);
1147 return -EINVAL;
1148 }
1149
1150 if (env->prog->aux->ops->get_func_proto)
1151 fn = env->prog->aux->ops->get_func_proto(func_id);
1152
1153 if (!fn) {
1154 verbose("unknown func %d\n", func_id);
1155 return -EINVAL;
1156 }
1157
1158 /* eBPF programs must be GPL compatible to use GPL-ed functions */
1159 if (!env->prog->gpl_compatible && fn->gpl_only) {
1160 verbose("cannot call GPL only function from proprietary program\n");
1161 return -EINVAL;
1162 }
1163
1164 changes_data = bpf_helper_changes_skb_data(fn->func);
1165
1166 memset(&meta, 0, sizeof(meta));
1167
1168 /* We only support one arg being in raw mode at the moment, which
1169 * is sufficient for the helper functions we have right now.
1170 */
1171 err = check_raw_mode(fn);
1172 if (err) {
1173 verbose("kernel subsystem misconfigured func %d\n", func_id);
1174 return err;
1175 }
1176
1177 /* check args */
1178 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
1179 if (err)
1180 return err;
1181 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
1182 if (err)
1183 return err;
1184 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
1185 if (err)
1186 return err;
1187 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
1188 if (err)
1189 return err;
1190 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
1191 if (err)
1192 return err;
1193
1194 /* Mark slots with STACK_MISC in case of raw mode, stack offset
1195 * is inferred from register state.
1196 */
1197 for (i = 0; i < meta.access_size; i++) {
1198 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1);
1199 if (err)
1200 return err;
1201 }
1202
1203 /* reset caller saved regs */
1204 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1205 reg = regs + caller_saved[i];
1206 reg->type = NOT_INIT;
1207 reg->imm = 0;
1208 }
1209
1210 /* update return register */
1211 if (fn->ret_type == RET_INTEGER) {
1212 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1213 } else if (fn->ret_type == RET_VOID) {
1214 regs[BPF_REG_0].type = NOT_INIT;
1215 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
1216 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
1217 /* remember map_ptr, so that check_map_access()
1218 * can check 'value_size' boundary of memory access
1219 * to map element returned from bpf_map_lookup_elem()
1220 */
1221 if (meta.map_ptr == NULL) {
1222 verbose("kernel subsystem misconfigured verifier\n");
1223 return -EINVAL;
1224 }
1225 regs[BPF_REG_0].map_ptr = meta.map_ptr;
1226 } else {
1227 verbose("unknown return type %d of func %d\n",
1228 fn->ret_type, func_id);
1229 return -EINVAL;
1230 }
1231
1232 err = check_map_func_compatibility(meta.map_ptr, func_id);
1233 if (err)
1234 return err;
1235
1236 if (changes_data)
1237 clear_all_pkt_pointers(env);
1238 return 0;
1239 }
1240
1241 static int check_packet_ptr_add(struct verifier_env *env, struct bpf_insn *insn)
1242 {
1243 struct reg_state *regs = env->cur_state.regs;
1244 struct reg_state *dst_reg = &regs[insn->dst_reg];
1245 struct reg_state *src_reg = &regs[insn->src_reg];
1246 struct reg_state tmp_reg;
1247 s32 imm;
1248
1249 if (BPF_SRC(insn->code) == BPF_K) {
1250 /* pkt_ptr += imm */
1251 imm = insn->imm;
1252
1253 add_imm:
1254 if (imm <= 0) {
1255 verbose("addition of negative constant to packet pointer is not allowed\n");
1256 return -EACCES;
1257 }
1258 if (imm >= MAX_PACKET_OFF ||
1259 imm + dst_reg->off >= MAX_PACKET_OFF) {
1260 verbose("constant %d is too large to add to packet pointer\n",
1261 imm);
1262 return -EACCES;
1263 }
1264 /* a constant was added to pkt_ptr.
1265 * Remember it while keeping the same 'id'
1266 */
1267 dst_reg->off += imm;
1268 } else {
1269 if (src_reg->type == PTR_TO_PACKET) {
1270 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */
1271 tmp_reg = *dst_reg; /* save r7 state */
1272 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */
1273 src_reg = &tmp_reg; /* pretend it's src_reg state */
1274 /* if the checks below reject it, the copy won't matter,
1275 * since we're rejecting the whole program. If all ok,
1276 * then imm22 state will be added to r7
1277 * and r7 will be pkt(id=0,off=22,r=62) while
1278 * r6 will stay as pkt(id=0,off=0,r=62)
1279 */
1280 }
1281
1282 if (src_reg->type == CONST_IMM) {
1283 /* pkt_ptr += reg where reg is known constant */
1284 imm = src_reg->imm;
1285 goto add_imm;
1286 }
1287 /* disallow pkt_ptr += reg
1288 * if reg is not uknown_value with guaranteed zero upper bits
1289 * otherwise pkt_ptr may overflow and addition will become
1290 * subtraction which is not allowed
1291 */
1292 if (src_reg->type != UNKNOWN_VALUE) {
1293 verbose("cannot add '%s' to ptr_to_packet\n",
1294 reg_type_str[src_reg->type]);
1295 return -EACCES;
1296 }
1297 if (src_reg->imm < 48) {
1298 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n",
1299 src_reg->imm);
1300 return -EACCES;
1301 }
1302 /* dst_reg stays as pkt_ptr type and since some positive
1303 * integer value was added to the pointer, increment its 'id'
1304 */
1305 dst_reg->id = ++env->id_gen;
1306
1307 /* something was added to pkt_ptr, set range and off to zero */
1308 dst_reg->off = 0;
1309 dst_reg->range = 0;
1310 }
1311 return 0;
1312 }
1313
1314 static int evaluate_reg_alu(struct verifier_env *env, struct bpf_insn *insn)
1315 {
1316 struct reg_state *regs = env->cur_state.regs;
1317 struct reg_state *dst_reg = &regs[insn->dst_reg];
1318 u8 opcode = BPF_OP(insn->code);
1319 s64 imm_log2;
1320
1321 /* for type == UNKNOWN_VALUE:
1322 * imm > 0 -> number of zero upper bits
1323 * imm == 0 -> don't track which is the same as all bits can be non-zero
1324 */
1325
1326 if (BPF_SRC(insn->code) == BPF_X) {
1327 struct reg_state *src_reg = &regs[insn->src_reg];
1328
1329 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 &&
1330 dst_reg->imm && opcode == BPF_ADD) {
1331 /* dreg += sreg
1332 * where both have zero upper bits. Adding them
1333 * can only result making one more bit non-zero
1334 * in the larger value.
1335 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47)
1336 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47)
1337 */
1338 dst_reg->imm = min(dst_reg->imm, src_reg->imm);
1339 dst_reg->imm--;
1340 return 0;
1341 }
1342 if (src_reg->type == CONST_IMM && src_reg->imm > 0 &&
1343 dst_reg->imm && opcode == BPF_ADD) {
1344 /* dreg += sreg
1345 * where dreg has zero upper bits and sreg is const.
1346 * Adding them can only result making one more bit
1347 * non-zero in the larger value.
1348 */
1349 imm_log2 = __ilog2_u64((long long)src_reg->imm);
1350 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
1351 dst_reg->imm--;
1352 return 0;
1353 }
1354 /* all other cases non supported yet, just mark dst_reg */
1355 dst_reg->imm = 0;
1356 return 0;
1357 }
1358
1359 /* sign extend 32-bit imm into 64-bit to make sure that
1360 * negative values occupy bit 63. Note ilog2() would have
1361 * been incorrect, since sizeof(insn->imm) == 4
1362 */
1363 imm_log2 = __ilog2_u64((long long)insn->imm);
1364
1365 if (dst_reg->imm && opcode == BPF_LSH) {
1366 /* reg <<= imm
1367 * if reg was a result of 2 byte load, then its imm == 48
1368 * which means that upper 48 bits are zero and shifting this reg
1369 * left by 4 would mean that upper 44 bits are still zero
1370 */
1371 dst_reg->imm -= insn->imm;
1372 } else if (dst_reg->imm && opcode == BPF_MUL) {
1373 /* reg *= imm
1374 * if multiplying by 14 subtract 4
1375 * This is conservative calculation of upper zero bits.
1376 * It's not trying to special case insn->imm == 1 or 0 cases
1377 */
1378 dst_reg->imm -= imm_log2 + 1;
1379 } else if (opcode == BPF_AND) {
1380 /* reg &= imm */
1381 dst_reg->imm = 63 - imm_log2;
1382 } else if (dst_reg->imm && opcode == BPF_ADD) {
1383 /* reg += imm */
1384 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
1385 dst_reg->imm--;
1386 } else if (opcode == BPF_RSH) {
1387 /* reg >>= imm
1388 * which means that after right shift, upper bits will be zero
1389 * note that verifier already checked that
1390 * 0 <= imm < 64 for shift insn
1391 */
1392 dst_reg->imm += insn->imm;
1393 if (unlikely(dst_reg->imm > 64))
1394 /* some dumb code did:
1395 * r2 = *(u32 *)mem;
1396 * r2 >>= 32;
1397 * and all bits are zero now */
1398 dst_reg->imm = 64;
1399 } else {
1400 /* all other alu ops, means that we don't know what will
1401 * happen to the value, mark it with unknown number of zero bits
1402 */
1403 dst_reg->imm = 0;
1404 }
1405
1406 if (dst_reg->imm < 0) {
1407 /* all 64 bits of the register can contain non-zero bits
1408 * and such value cannot be added to ptr_to_packet, since it
1409 * may overflow, mark it as unknown to avoid further eval
1410 */
1411 dst_reg->imm = 0;
1412 }
1413 return 0;
1414 }
1415
1416 static int evaluate_reg_imm_alu(struct verifier_env *env, struct bpf_insn *insn)
1417 {
1418 struct reg_state *regs = env->cur_state.regs;
1419 struct reg_state *dst_reg = &regs[insn->dst_reg];
1420 struct reg_state *src_reg = &regs[insn->src_reg];
1421 u8 opcode = BPF_OP(insn->code);
1422
1423 /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn.
1424 * Don't care about overflow or negative values, just add them
1425 */
1426 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K)
1427 dst_reg->imm += insn->imm;
1428 else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X &&
1429 src_reg->type == CONST_IMM)
1430 dst_reg->imm += src_reg->imm;
1431 else
1432 mark_reg_unknown_value(regs, insn->dst_reg);
1433 return 0;
1434 }
1435
1436 /* check validity of 32-bit and 64-bit arithmetic operations */
1437 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn)
1438 {
1439 struct reg_state *regs = env->cur_state.regs, *dst_reg;
1440 u8 opcode = BPF_OP(insn->code);
1441 int err;
1442
1443 if (opcode == BPF_END || opcode == BPF_NEG) {
1444 if (opcode == BPF_NEG) {
1445 if (BPF_SRC(insn->code) != 0 ||
1446 insn->src_reg != BPF_REG_0 ||
1447 insn->off != 0 || insn->imm != 0) {
1448 verbose("BPF_NEG uses reserved fields\n");
1449 return -EINVAL;
1450 }
1451 } else {
1452 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1453 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1454 verbose("BPF_END uses reserved fields\n");
1455 return -EINVAL;
1456 }
1457 }
1458
1459 /* check src operand */
1460 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1461 if (err)
1462 return err;
1463
1464 if (is_pointer_value(env, insn->dst_reg)) {
1465 verbose("R%d pointer arithmetic prohibited\n",
1466 insn->dst_reg);
1467 return -EACCES;
1468 }
1469
1470 /* check dest operand */
1471 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1472 if (err)
1473 return err;
1474
1475 } else if (opcode == BPF_MOV) {
1476
1477 if (BPF_SRC(insn->code) == BPF_X) {
1478 if (insn->imm != 0 || insn->off != 0) {
1479 verbose("BPF_MOV uses reserved fields\n");
1480 return -EINVAL;
1481 }
1482
1483 /* check src operand */
1484 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1485 if (err)
1486 return err;
1487 } else {
1488 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1489 verbose("BPF_MOV uses reserved fields\n");
1490 return -EINVAL;
1491 }
1492 }
1493
1494 /* check dest operand */
1495 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1496 if (err)
1497 return err;
1498
1499 if (BPF_SRC(insn->code) == BPF_X) {
1500 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1501 /* case: R1 = R2
1502 * copy register state to dest reg
1503 */
1504 regs[insn->dst_reg] = regs[insn->src_reg];
1505 } else {
1506 if (is_pointer_value(env, insn->src_reg)) {
1507 verbose("R%d partial copy of pointer\n",
1508 insn->src_reg);
1509 return -EACCES;
1510 }
1511 regs[insn->dst_reg].type = UNKNOWN_VALUE;
1512 regs[insn->dst_reg].map_ptr = NULL;
1513 }
1514 } else {
1515 /* case: R = imm
1516 * remember the value we stored into this reg
1517 */
1518 regs[insn->dst_reg].type = CONST_IMM;
1519 regs[insn->dst_reg].imm = insn->imm;
1520 }
1521
1522 } else if (opcode > BPF_END) {
1523 verbose("invalid BPF_ALU opcode %x\n", opcode);
1524 return -EINVAL;
1525
1526 } else { /* all other ALU ops: and, sub, xor, add, ... */
1527
1528 if (BPF_SRC(insn->code) == BPF_X) {
1529 if (insn->imm != 0 || insn->off != 0) {
1530 verbose("BPF_ALU uses reserved fields\n");
1531 return -EINVAL;
1532 }
1533 /* check src1 operand */
1534 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1535 if (err)
1536 return err;
1537 } else {
1538 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1539 verbose("BPF_ALU uses reserved fields\n");
1540 return -EINVAL;
1541 }
1542 }
1543
1544 /* check src2 operand */
1545 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1546 if (err)
1547 return err;
1548
1549 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1550 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1551 verbose("div by zero\n");
1552 return -EINVAL;
1553 }
1554
1555 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1556 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1557 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1558
1559 if (insn->imm < 0 || insn->imm >= size) {
1560 verbose("invalid shift %d\n", insn->imm);
1561 return -EINVAL;
1562 }
1563 }
1564
1565 /* check dest operand */
1566 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1567 if (err)
1568 return err;
1569
1570 dst_reg = &regs[insn->dst_reg];
1571
1572 /* pattern match 'bpf_add Rx, imm' instruction */
1573 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1574 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) {
1575 dst_reg->type = PTR_TO_STACK;
1576 dst_reg->imm = insn->imm;
1577 return 0;
1578 } else if (opcode == BPF_ADD &&
1579 BPF_CLASS(insn->code) == BPF_ALU64 &&
1580 (dst_reg->type == PTR_TO_PACKET ||
1581 (BPF_SRC(insn->code) == BPF_X &&
1582 regs[insn->src_reg].type == PTR_TO_PACKET))) {
1583 /* ptr_to_packet += K|X */
1584 return check_packet_ptr_add(env, insn);
1585 } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
1586 dst_reg->type == UNKNOWN_VALUE &&
1587 env->allow_ptr_leaks) {
1588 /* unknown += K|X */
1589 return evaluate_reg_alu(env, insn);
1590 } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
1591 dst_reg->type == CONST_IMM &&
1592 env->allow_ptr_leaks) {
1593 /* reg_imm += K|X */
1594 return evaluate_reg_imm_alu(env, insn);
1595 } else if (is_pointer_value(env, insn->dst_reg)) {
1596 verbose("R%d pointer arithmetic prohibited\n",
1597 insn->dst_reg);
1598 return -EACCES;
1599 } else if (BPF_SRC(insn->code) == BPF_X &&
1600 is_pointer_value(env, insn->src_reg)) {
1601 verbose("R%d pointer arithmetic prohibited\n",
1602 insn->src_reg);
1603 return -EACCES;
1604 }
1605
1606 /* mark dest operand */
1607 mark_reg_unknown_value(regs, insn->dst_reg);
1608 }
1609
1610 return 0;
1611 }
1612
1613 static void find_good_pkt_pointers(struct verifier_env *env,
1614 struct reg_state *dst_reg)
1615 {
1616 struct verifier_state *state = &env->cur_state;
1617 struct reg_state *regs = state->regs, *reg;
1618 int i;
1619 /* r2 = r3;
1620 * r2 += 8
1621 * if (r2 > pkt_end) goto somewhere
1622 * r2 == dst_reg, pkt_end == src_reg,
1623 * r2=pkt(id=n,off=8,r=0)
1624 * r3=pkt(id=n,off=0,r=0)
1625 * find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
1626 * so that range of bytes [r3, r3 + 8) is safe to access
1627 */
1628 for (i = 0; i < MAX_BPF_REG; i++)
1629 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
1630 regs[i].range = dst_reg->off;
1631
1632 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1633 if (state->stack_slot_type[i] != STACK_SPILL)
1634 continue;
1635 reg = &state->spilled_regs[i / BPF_REG_SIZE];
1636 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
1637 reg->range = dst_reg->off;
1638 }
1639 }
1640
1641 static int check_cond_jmp_op(struct verifier_env *env,
1642 struct bpf_insn *insn, int *insn_idx)
1643 {
1644 struct reg_state *regs = env->cur_state.regs, *dst_reg;
1645 struct verifier_state *other_branch;
1646 u8 opcode = BPF_OP(insn->code);
1647 int err;
1648
1649 if (opcode > BPF_EXIT) {
1650 verbose("invalid BPF_JMP opcode %x\n", opcode);
1651 return -EINVAL;
1652 }
1653
1654 if (BPF_SRC(insn->code) == BPF_X) {
1655 if (insn->imm != 0) {
1656 verbose("BPF_JMP uses reserved fields\n");
1657 return -EINVAL;
1658 }
1659
1660 /* check src1 operand */
1661 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1662 if (err)
1663 return err;
1664
1665 if (is_pointer_value(env, insn->src_reg)) {
1666 verbose("R%d pointer comparison prohibited\n",
1667 insn->src_reg);
1668 return -EACCES;
1669 }
1670 } else {
1671 if (insn->src_reg != BPF_REG_0) {
1672 verbose("BPF_JMP uses reserved fields\n");
1673 return -EINVAL;
1674 }
1675 }
1676
1677 /* check src2 operand */
1678 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1679 if (err)
1680 return err;
1681
1682 dst_reg = &regs[insn->dst_reg];
1683
1684 /* detect if R == 0 where R was initialized to zero earlier */
1685 if (BPF_SRC(insn->code) == BPF_K &&
1686 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1687 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) {
1688 if (opcode == BPF_JEQ) {
1689 /* if (imm == imm) goto pc+off;
1690 * only follow the goto, ignore fall-through
1691 */
1692 *insn_idx += insn->off;
1693 return 0;
1694 } else {
1695 /* if (imm != imm) goto pc+off;
1696 * only follow fall-through branch, since
1697 * that's where the program will go
1698 */
1699 return 0;
1700 }
1701 }
1702
1703 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1704 if (!other_branch)
1705 return -EFAULT;
1706
1707 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1708 if (BPF_SRC(insn->code) == BPF_K &&
1709 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1710 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
1711 if (opcode == BPF_JEQ) {
1712 /* next fallthrough insn can access memory via
1713 * this register
1714 */
1715 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1716 /* branch targer cannot access it, since reg == 0 */
1717 mark_reg_unknown_value(other_branch->regs,
1718 insn->dst_reg);
1719 } else {
1720 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1721 mark_reg_unknown_value(regs, insn->dst_reg);
1722 }
1723 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
1724 dst_reg->type == PTR_TO_PACKET &&
1725 regs[insn->src_reg].type == PTR_TO_PACKET_END) {
1726 find_good_pkt_pointers(env, dst_reg);
1727 } else if (is_pointer_value(env, insn->dst_reg)) {
1728 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
1729 return -EACCES;
1730 }
1731 if (log_level)
1732 print_verifier_state(&env->cur_state);
1733 return 0;
1734 }
1735
1736 /* return the map pointer stored inside BPF_LD_IMM64 instruction */
1737 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1738 {
1739 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1740
1741 return (struct bpf_map *) (unsigned long) imm64;
1742 }
1743
1744 /* verify BPF_LD_IMM64 instruction */
1745 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1746 {
1747 struct reg_state *regs = env->cur_state.regs;
1748 int err;
1749
1750 if (BPF_SIZE(insn->code) != BPF_DW) {
1751 verbose("invalid BPF_LD_IMM insn\n");
1752 return -EINVAL;
1753 }
1754 if (insn->off != 0) {
1755 verbose("BPF_LD_IMM64 uses reserved fields\n");
1756 return -EINVAL;
1757 }
1758
1759 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1760 if (err)
1761 return err;
1762
1763 if (insn->src_reg == 0)
1764 /* generic move 64-bit immediate into a register */
1765 return 0;
1766
1767 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1768 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1769
1770 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1771 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1772 return 0;
1773 }
1774
1775 static bool may_access_skb(enum bpf_prog_type type)
1776 {
1777 switch (type) {
1778 case BPF_PROG_TYPE_SOCKET_FILTER:
1779 case BPF_PROG_TYPE_SCHED_CLS:
1780 case BPF_PROG_TYPE_SCHED_ACT:
1781 return true;
1782 default:
1783 return false;
1784 }
1785 }
1786
1787 /* verify safety of LD_ABS|LD_IND instructions:
1788 * - they can only appear in the programs where ctx == skb
1789 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1790 * preserve R6-R9, and store return value into R0
1791 *
1792 * Implicit input:
1793 * ctx == skb == R6 == CTX
1794 *
1795 * Explicit input:
1796 * SRC == any register
1797 * IMM == 32-bit immediate
1798 *
1799 * Output:
1800 * R0 - 8/16/32-bit skb data converted to cpu endianness
1801 */
1802 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1803 {
1804 struct reg_state *regs = env->cur_state.regs;
1805 u8 mode = BPF_MODE(insn->code);
1806 struct reg_state *reg;
1807 int i, err;
1808
1809 if (!may_access_skb(env->prog->type)) {
1810 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
1811 return -EINVAL;
1812 }
1813
1814 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1815 BPF_SIZE(insn->code) == BPF_DW ||
1816 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1817 verbose("BPF_LD_[ABS|IND] uses reserved fields\n");
1818 return -EINVAL;
1819 }
1820
1821 /* check whether implicit source operand (register R6) is readable */
1822 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1823 if (err)
1824 return err;
1825
1826 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1827 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1828 return -EINVAL;
1829 }
1830
1831 if (mode == BPF_IND) {
1832 /* check explicit source operand */
1833 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1834 if (err)
1835 return err;
1836 }
1837
1838 /* reset caller saved regs to unreadable */
1839 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1840 reg = regs + caller_saved[i];
1841 reg->type = NOT_INIT;
1842 reg->imm = 0;
1843 }
1844
1845 /* mark destination R0 register as readable, since it contains
1846 * the value fetched from the packet
1847 */
1848 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1849 return 0;
1850 }
1851
1852 /* non-recursive DFS pseudo code
1853 * 1 procedure DFS-iterative(G,v):
1854 * 2 label v as discovered
1855 * 3 let S be a stack
1856 * 4 S.push(v)
1857 * 5 while S is not empty
1858 * 6 t <- S.pop()
1859 * 7 if t is what we're looking for:
1860 * 8 return t
1861 * 9 for all edges e in G.adjacentEdges(t) do
1862 * 10 if edge e is already labelled
1863 * 11 continue with the next edge
1864 * 12 w <- G.adjacentVertex(t,e)
1865 * 13 if vertex w is not discovered and not explored
1866 * 14 label e as tree-edge
1867 * 15 label w as discovered
1868 * 16 S.push(w)
1869 * 17 continue at 5
1870 * 18 else if vertex w is discovered
1871 * 19 label e as back-edge
1872 * 20 else
1873 * 21 // vertex w is explored
1874 * 22 label e as forward- or cross-edge
1875 * 23 label t as explored
1876 * 24 S.pop()
1877 *
1878 * convention:
1879 * 0x10 - discovered
1880 * 0x11 - discovered and fall-through edge labelled
1881 * 0x12 - discovered and fall-through and branch edges labelled
1882 * 0x20 - explored
1883 */
1884
1885 enum {
1886 DISCOVERED = 0x10,
1887 EXPLORED = 0x20,
1888 FALLTHROUGH = 1,
1889 BRANCH = 2,
1890 };
1891
1892 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1893
1894 static int *insn_stack; /* stack of insns to process */
1895 static int cur_stack; /* current stack index */
1896 static int *insn_state;
1897
1898 /* t, w, e - match pseudo-code above:
1899 * t - index of current instruction
1900 * w - next instruction
1901 * e - edge
1902 */
1903 static int push_insn(int t, int w, int e, struct verifier_env *env)
1904 {
1905 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1906 return 0;
1907
1908 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1909 return 0;
1910
1911 if (w < 0 || w >= env->prog->len) {
1912 verbose("jump out of range from insn %d to %d\n", t, w);
1913 return -EINVAL;
1914 }
1915
1916 if (e == BRANCH)
1917 /* mark branch target for state pruning */
1918 env->explored_states[w] = STATE_LIST_MARK;
1919
1920 if (insn_state[w] == 0) {
1921 /* tree-edge */
1922 insn_state[t] = DISCOVERED | e;
1923 insn_state[w] = DISCOVERED;
1924 if (cur_stack >= env->prog->len)
1925 return -E2BIG;
1926 insn_stack[cur_stack++] = w;
1927 return 1;
1928 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1929 verbose("back-edge from insn %d to %d\n", t, w);
1930 return -EINVAL;
1931 } else if (insn_state[w] == EXPLORED) {
1932 /* forward- or cross-edge */
1933 insn_state[t] = DISCOVERED | e;
1934 } else {
1935 verbose("insn state internal bug\n");
1936 return -EFAULT;
1937 }
1938 return 0;
1939 }
1940
1941 /* non-recursive depth-first-search to detect loops in BPF program
1942 * loop == back-edge in directed graph
1943 */
1944 static int check_cfg(struct verifier_env *env)
1945 {
1946 struct bpf_insn *insns = env->prog->insnsi;
1947 int insn_cnt = env->prog->len;
1948 int ret = 0;
1949 int i, t;
1950
1951 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1952 if (!insn_state)
1953 return -ENOMEM;
1954
1955 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1956 if (!insn_stack) {
1957 kfree(insn_state);
1958 return -ENOMEM;
1959 }
1960
1961 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1962 insn_stack[0] = 0; /* 0 is the first instruction */
1963 cur_stack = 1;
1964
1965 peek_stack:
1966 if (cur_stack == 0)
1967 goto check_state;
1968 t = insn_stack[cur_stack - 1];
1969
1970 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1971 u8 opcode = BPF_OP(insns[t].code);
1972
1973 if (opcode == BPF_EXIT) {
1974 goto mark_explored;
1975 } else if (opcode == BPF_CALL) {
1976 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1977 if (ret == 1)
1978 goto peek_stack;
1979 else if (ret < 0)
1980 goto err_free;
1981 if (t + 1 < insn_cnt)
1982 env->explored_states[t + 1] = STATE_LIST_MARK;
1983 } else if (opcode == BPF_JA) {
1984 if (BPF_SRC(insns[t].code) != BPF_K) {
1985 ret = -EINVAL;
1986 goto err_free;
1987 }
1988 /* unconditional jump with single edge */
1989 ret = push_insn(t, t + insns[t].off + 1,
1990 FALLTHROUGH, env);
1991 if (ret == 1)
1992 goto peek_stack;
1993 else if (ret < 0)
1994 goto err_free;
1995 /* tell verifier to check for equivalent states
1996 * after every call and jump
1997 */
1998 if (t + 1 < insn_cnt)
1999 env->explored_states[t + 1] = STATE_LIST_MARK;
2000 } else {
2001 /* conditional jump with two edges */
2002 ret = push_insn(t, t + 1, FALLTHROUGH, env);
2003 if (ret == 1)
2004 goto peek_stack;
2005 else if (ret < 0)
2006 goto err_free;
2007
2008 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
2009 if (ret == 1)
2010 goto peek_stack;
2011 else if (ret < 0)
2012 goto err_free;
2013 }
2014 } else {
2015 /* all other non-branch instructions with single
2016 * fall-through edge
2017 */
2018 ret = push_insn(t, t + 1, FALLTHROUGH, env);
2019 if (ret == 1)
2020 goto peek_stack;
2021 else if (ret < 0)
2022 goto err_free;
2023 }
2024
2025 mark_explored:
2026 insn_state[t] = EXPLORED;
2027 if (cur_stack-- <= 0) {
2028 verbose("pop stack internal bug\n");
2029 ret = -EFAULT;
2030 goto err_free;
2031 }
2032 goto peek_stack;
2033
2034 check_state:
2035 for (i = 0; i < insn_cnt; i++) {
2036 if (insn_state[i] != EXPLORED) {
2037 verbose("unreachable insn %d\n", i);
2038 ret = -EINVAL;
2039 goto err_free;
2040 }
2041 }
2042 ret = 0; /* cfg looks good */
2043
2044 err_free:
2045 kfree(insn_state);
2046 kfree(insn_stack);
2047 return ret;
2048 }
2049
2050 /* the following conditions reduce the number of explored insns
2051 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet
2052 */
2053 static bool compare_ptrs_to_packet(struct reg_state *old, struct reg_state *cur)
2054 {
2055 if (old->id != cur->id)
2056 return false;
2057
2058 /* old ptr_to_packet is more conservative, since it allows smaller
2059 * range. Ex:
2060 * old(off=0,r=10) is equal to cur(off=0,r=20), because
2061 * old(off=0,r=10) means that with range=10 the verifier proceeded
2062 * further and found no issues with the program. Now we're in the same
2063 * spot with cur(off=0,r=20), so we're safe too, since anything further
2064 * will only be looking at most 10 bytes after this pointer.
2065 */
2066 if (old->off == cur->off && old->range < cur->range)
2067 return true;
2068
2069 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0)
2070 * since both cannot be used for packet access and safe(old)
2071 * pointer has smaller off that could be used for further
2072 * 'if (ptr > data_end)' check
2073 * Ex:
2074 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean
2075 * that we cannot access the packet.
2076 * The safe range is:
2077 * [ptr, ptr + range - off)
2078 * so whenever off >=range, it means no safe bytes from this pointer.
2079 * When comparing old->off <= cur->off, it means that older code
2080 * went with smaller offset and that offset was later
2081 * used to figure out the safe range after 'if (ptr > data_end)' check
2082 * Say, 'old' state was explored like:
2083 * ... R3(off=0, r=0)
2084 * R4 = R3 + 20
2085 * ... now R4(off=20,r=0) <-- here
2086 * if (R4 > data_end)
2087 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access.
2088 * ... the code further went all the way to bpf_exit.
2089 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0).
2090 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier
2091 * goes further, such cur_R4 will give larger safe packet range after
2092 * 'if (R4 > data_end)' and all further insn were already good with r=20,
2093 * so they will be good with r=30 and we can prune the search.
2094 */
2095 if (old->off <= cur->off &&
2096 old->off >= old->range && cur->off >= cur->range)
2097 return true;
2098
2099 return false;
2100 }
2101
2102 /* compare two verifier states
2103 *
2104 * all states stored in state_list are known to be valid, since
2105 * verifier reached 'bpf_exit' instruction through them
2106 *
2107 * this function is called when verifier exploring different branches of
2108 * execution popped from the state stack. If it sees an old state that has
2109 * more strict register state and more strict stack state then this execution
2110 * branch doesn't need to be explored further, since verifier already
2111 * concluded that more strict state leads to valid finish.
2112 *
2113 * Therefore two states are equivalent if register state is more conservative
2114 * and explored stack state is more conservative than the current one.
2115 * Example:
2116 * explored current
2117 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
2118 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
2119 *
2120 * In other words if current stack state (one being explored) has more
2121 * valid slots than old one that already passed validation, it means
2122 * the verifier can stop exploring and conclude that current state is valid too
2123 *
2124 * Similarly with registers. If explored state has register type as invalid
2125 * whereas register type in current state is meaningful, it means that
2126 * the current state will reach 'bpf_exit' instruction safely
2127 */
2128 static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
2129 {
2130 struct reg_state *rold, *rcur;
2131 int i;
2132
2133 for (i = 0; i < MAX_BPF_REG; i++) {
2134 rold = &old->regs[i];
2135 rcur = &cur->regs[i];
2136
2137 if (memcmp(rold, rcur, sizeof(*rold)) == 0)
2138 continue;
2139
2140 if (rold->type == NOT_INIT ||
2141 (rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT))
2142 continue;
2143
2144 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET &&
2145 compare_ptrs_to_packet(rold, rcur))
2146 continue;
2147
2148 return false;
2149 }
2150
2151 for (i = 0; i < MAX_BPF_STACK; i++) {
2152 if (old->stack_slot_type[i] == STACK_INVALID)
2153 continue;
2154 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
2155 /* Ex: old explored (safe) state has STACK_SPILL in
2156 * this stack slot, but current has has STACK_MISC ->
2157 * this verifier states are not equivalent,
2158 * return false to continue verification of this path
2159 */
2160 return false;
2161 if (i % BPF_REG_SIZE)
2162 continue;
2163 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
2164 &cur->spilled_regs[i / BPF_REG_SIZE],
2165 sizeof(old->spilled_regs[0])))
2166 /* when explored and current stack slot types are
2167 * the same, check that stored pointers types
2168 * are the same as well.
2169 * Ex: explored safe path could have stored
2170 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
2171 * but current path has stored:
2172 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
2173 * such verifier states are not equivalent.
2174 * return false to continue verification of this path
2175 */
2176 return false;
2177 else
2178 continue;
2179 }
2180 return true;
2181 }
2182
2183 static int is_state_visited(struct verifier_env *env, int insn_idx)
2184 {
2185 struct verifier_state_list *new_sl;
2186 struct verifier_state_list *sl;
2187
2188 sl = env->explored_states[insn_idx];
2189 if (!sl)
2190 /* this 'insn_idx' instruction wasn't marked, so we will not
2191 * be doing state search here
2192 */
2193 return 0;
2194
2195 while (sl != STATE_LIST_MARK) {
2196 if (states_equal(&sl->state, &env->cur_state))
2197 /* reached equivalent register/stack state,
2198 * prune the search
2199 */
2200 return 1;
2201 sl = sl->next;
2202 }
2203
2204 /* there were no equivalent states, remember current one.
2205 * technically the current state is not proven to be safe yet,
2206 * but it will either reach bpf_exit (which means it's safe) or
2207 * it will be rejected. Since there are no loops, we won't be
2208 * seeing this 'insn_idx' instruction again on the way to bpf_exit
2209 */
2210 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
2211 if (!new_sl)
2212 return -ENOMEM;
2213
2214 /* add new state to the head of linked list */
2215 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
2216 new_sl->next = env->explored_states[insn_idx];
2217 env->explored_states[insn_idx] = new_sl;
2218 return 0;
2219 }
2220
2221 static int do_check(struct verifier_env *env)
2222 {
2223 struct verifier_state *state = &env->cur_state;
2224 struct bpf_insn *insns = env->prog->insnsi;
2225 struct reg_state *regs = state->regs;
2226 int insn_cnt = env->prog->len;
2227 int insn_idx, prev_insn_idx = 0;
2228 int insn_processed = 0;
2229 bool do_print_state = false;
2230
2231 init_reg_state(regs);
2232 insn_idx = 0;
2233 for (;;) {
2234 struct bpf_insn *insn;
2235 u8 class;
2236 int err;
2237
2238 if (insn_idx >= insn_cnt) {
2239 verbose("invalid insn idx %d insn_cnt %d\n",
2240 insn_idx, insn_cnt);
2241 return -EFAULT;
2242 }
2243
2244 insn = &insns[insn_idx];
2245 class = BPF_CLASS(insn->code);
2246
2247 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
2248 verbose("BPF program is too large. Proccessed %d insn\n",
2249 insn_processed);
2250 return -E2BIG;
2251 }
2252
2253 err = is_state_visited(env, insn_idx);
2254 if (err < 0)
2255 return err;
2256 if (err == 1) {
2257 /* found equivalent state, can prune the search */
2258 if (log_level) {
2259 if (do_print_state)
2260 verbose("\nfrom %d to %d: safe\n",
2261 prev_insn_idx, insn_idx);
2262 else
2263 verbose("%d: safe\n", insn_idx);
2264 }
2265 goto process_bpf_exit;
2266 }
2267
2268 if (log_level && do_print_state) {
2269 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
2270 print_verifier_state(&env->cur_state);
2271 do_print_state = false;
2272 }
2273
2274 if (log_level) {
2275 verbose("%d: ", insn_idx);
2276 print_bpf_insn(insn);
2277 }
2278
2279 if (class == BPF_ALU || class == BPF_ALU64) {
2280 err = check_alu_op(env, insn);
2281 if (err)
2282 return err;
2283
2284 } else if (class == BPF_LDX) {
2285 enum bpf_reg_type src_reg_type;
2286
2287 /* check for reserved fields is already done */
2288
2289 /* check src operand */
2290 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2291 if (err)
2292 return err;
2293
2294 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
2295 if (err)
2296 return err;
2297
2298 src_reg_type = regs[insn->src_reg].type;
2299
2300 /* check that memory (src_reg + off) is readable,
2301 * the state of dst_reg will be updated by this func
2302 */
2303 err = check_mem_access(env, insn->src_reg, insn->off,
2304 BPF_SIZE(insn->code), BPF_READ,
2305 insn->dst_reg);
2306 if (err)
2307 return err;
2308
2309 if (BPF_SIZE(insn->code) != BPF_W) {
2310 insn_idx++;
2311 continue;
2312 }
2313
2314 if (insn->imm == 0) {
2315 /* saw a valid insn
2316 * dst_reg = *(u32 *)(src_reg + off)
2317 * use reserved 'imm' field to mark this insn
2318 */
2319 insn->imm = src_reg_type;
2320
2321 } else if (src_reg_type != insn->imm &&
2322 (src_reg_type == PTR_TO_CTX ||
2323 insn->imm == PTR_TO_CTX)) {
2324 /* ABuser program is trying to use the same insn
2325 * dst_reg = *(u32*) (src_reg + off)
2326 * with different pointer types:
2327 * src_reg == ctx in one branch and
2328 * src_reg == stack|map in some other branch.
2329 * Reject it.
2330 */
2331 verbose("same insn cannot be used with different pointers\n");
2332 return -EINVAL;
2333 }
2334
2335 } else if (class == BPF_STX) {
2336 enum bpf_reg_type dst_reg_type;
2337
2338 if (BPF_MODE(insn->code) == BPF_XADD) {
2339 err = check_xadd(env, insn);
2340 if (err)
2341 return err;
2342 insn_idx++;
2343 continue;
2344 }
2345
2346 /* check src1 operand */
2347 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2348 if (err)
2349 return err;
2350 /* check src2 operand */
2351 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2352 if (err)
2353 return err;
2354
2355 dst_reg_type = regs[insn->dst_reg].type;
2356
2357 /* check that memory (dst_reg + off) is writeable */
2358 err = check_mem_access(env, insn->dst_reg, insn->off,
2359 BPF_SIZE(insn->code), BPF_WRITE,
2360 insn->src_reg);
2361 if (err)
2362 return err;
2363
2364 if (insn->imm == 0) {
2365 insn->imm = dst_reg_type;
2366 } else if (dst_reg_type != insn->imm &&
2367 (dst_reg_type == PTR_TO_CTX ||
2368 insn->imm == PTR_TO_CTX)) {
2369 verbose("same insn cannot be used with different pointers\n");
2370 return -EINVAL;
2371 }
2372
2373 } else if (class == BPF_ST) {
2374 if (BPF_MODE(insn->code) != BPF_MEM ||
2375 insn->src_reg != BPF_REG_0) {
2376 verbose("BPF_ST uses reserved fields\n");
2377 return -EINVAL;
2378 }
2379 /* check src operand */
2380 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2381 if (err)
2382 return err;
2383
2384 /* check that memory (dst_reg + off) is writeable */
2385 err = check_mem_access(env, insn->dst_reg, insn->off,
2386 BPF_SIZE(insn->code), BPF_WRITE,
2387 -1);
2388 if (err)
2389 return err;
2390
2391 } else if (class == BPF_JMP) {
2392 u8 opcode = BPF_OP(insn->code);
2393
2394 if (opcode == BPF_CALL) {
2395 if (BPF_SRC(insn->code) != BPF_K ||
2396 insn->off != 0 ||
2397 insn->src_reg != BPF_REG_0 ||
2398 insn->dst_reg != BPF_REG_0) {
2399 verbose("BPF_CALL uses reserved fields\n");
2400 return -EINVAL;
2401 }
2402
2403 err = check_call(env, insn->imm);
2404 if (err)
2405 return err;
2406
2407 } else if (opcode == BPF_JA) {
2408 if (BPF_SRC(insn->code) != BPF_K ||
2409 insn->imm != 0 ||
2410 insn->src_reg != BPF_REG_0 ||
2411 insn->dst_reg != BPF_REG_0) {
2412 verbose("BPF_JA uses reserved fields\n");
2413 return -EINVAL;
2414 }
2415
2416 insn_idx += insn->off + 1;
2417 continue;
2418
2419 } else if (opcode == BPF_EXIT) {
2420 if (BPF_SRC(insn->code) != BPF_K ||
2421 insn->imm != 0 ||
2422 insn->src_reg != BPF_REG_0 ||
2423 insn->dst_reg != BPF_REG_0) {
2424 verbose("BPF_EXIT uses reserved fields\n");
2425 return -EINVAL;
2426 }
2427
2428 /* eBPF calling convetion is such that R0 is used
2429 * to return the value from eBPF program.
2430 * Make sure that it's readable at this time
2431 * of bpf_exit, which means that program wrote
2432 * something into it earlier
2433 */
2434 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
2435 if (err)
2436 return err;
2437
2438 if (is_pointer_value(env, BPF_REG_0)) {
2439 verbose("R0 leaks addr as return value\n");
2440 return -EACCES;
2441 }
2442
2443 process_bpf_exit:
2444 insn_idx = pop_stack(env, &prev_insn_idx);
2445 if (insn_idx < 0) {
2446 break;
2447 } else {
2448 do_print_state = true;
2449 continue;
2450 }
2451 } else {
2452 err = check_cond_jmp_op(env, insn, &insn_idx);
2453 if (err)
2454 return err;
2455 }
2456 } else if (class == BPF_LD) {
2457 u8 mode = BPF_MODE(insn->code);
2458
2459 if (mode == BPF_ABS || mode == BPF_IND) {
2460 err = check_ld_abs(env, insn);
2461 if (err)
2462 return err;
2463
2464 } else if (mode == BPF_IMM) {
2465 err = check_ld_imm(env, insn);
2466 if (err)
2467 return err;
2468
2469 insn_idx++;
2470 } else {
2471 verbose("invalid BPF_LD mode\n");
2472 return -EINVAL;
2473 }
2474 } else {
2475 verbose("unknown insn class %d\n", class);
2476 return -EINVAL;
2477 }
2478
2479 insn_idx++;
2480 }
2481
2482 verbose("processed %d insns\n", insn_processed);
2483 return 0;
2484 }
2485
2486 /* look for pseudo eBPF instructions that access map FDs and
2487 * replace them with actual map pointers
2488 */
2489 static int replace_map_fd_with_map_ptr(struct verifier_env *env)
2490 {
2491 struct bpf_insn *insn = env->prog->insnsi;
2492 int insn_cnt = env->prog->len;
2493 int i, j;
2494
2495 for (i = 0; i < insn_cnt; i++, insn++) {
2496 if (BPF_CLASS(insn->code) == BPF_LDX &&
2497 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
2498 verbose("BPF_LDX uses reserved fields\n");
2499 return -EINVAL;
2500 }
2501
2502 if (BPF_CLASS(insn->code) == BPF_STX &&
2503 ((BPF_MODE(insn->code) != BPF_MEM &&
2504 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2505 verbose("BPF_STX uses reserved fields\n");
2506 return -EINVAL;
2507 }
2508
2509 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2510 struct bpf_map *map;
2511 struct fd f;
2512
2513 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2514 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2515 insn[1].off != 0) {
2516 verbose("invalid bpf_ld_imm64 insn\n");
2517 return -EINVAL;
2518 }
2519
2520 if (insn->src_reg == 0)
2521 /* valid generic load 64-bit imm */
2522 goto next_insn;
2523
2524 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2525 verbose("unrecognized bpf_ld_imm64 insn\n");
2526 return -EINVAL;
2527 }
2528
2529 f = fdget(insn->imm);
2530 map = __bpf_map_get(f);
2531 if (IS_ERR(map)) {
2532 verbose("fd %d is not pointing to valid bpf_map\n",
2533 insn->imm);
2534 return PTR_ERR(map);
2535 }
2536
2537 /* store map pointer inside BPF_LD_IMM64 instruction */
2538 insn[0].imm = (u32) (unsigned long) map;
2539 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2540
2541 /* check whether we recorded this map already */
2542 for (j = 0; j < env->used_map_cnt; j++)
2543 if (env->used_maps[j] == map) {
2544 fdput(f);
2545 goto next_insn;
2546 }
2547
2548 if (env->used_map_cnt >= MAX_USED_MAPS) {
2549 fdput(f);
2550 return -E2BIG;
2551 }
2552
2553 /* hold the map. If the program is rejected by verifier,
2554 * the map will be released by release_maps() or it
2555 * will be used by the valid program until it's unloaded
2556 * and all maps are released in free_bpf_prog_info()
2557 */
2558 map = bpf_map_inc(map, false);
2559 if (IS_ERR(map)) {
2560 fdput(f);
2561 return PTR_ERR(map);
2562 }
2563 env->used_maps[env->used_map_cnt++] = map;
2564
2565 fdput(f);
2566 next_insn:
2567 insn++;
2568 i++;
2569 }
2570 }
2571
2572 /* now all pseudo BPF_LD_IMM64 instructions load valid
2573 * 'struct bpf_map *' into a register instead of user map_fd.
2574 * These pointers will be used later by verifier to validate map access.
2575 */
2576 return 0;
2577 }
2578
2579 /* drop refcnt of maps used by the rejected program */
2580 static void release_maps(struct verifier_env *env)
2581 {
2582 int i;
2583
2584 for (i = 0; i < env->used_map_cnt; i++)
2585 bpf_map_put(env->used_maps[i]);
2586 }
2587
2588 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2589 static void convert_pseudo_ld_imm64(struct verifier_env *env)
2590 {
2591 struct bpf_insn *insn = env->prog->insnsi;
2592 int insn_cnt = env->prog->len;
2593 int i;
2594
2595 for (i = 0; i < insn_cnt; i++, insn++)
2596 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2597 insn->src_reg = 0;
2598 }
2599
2600 /* convert load instructions that access fields of 'struct __sk_buff'
2601 * into sequence of instructions that access fields of 'struct sk_buff'
2602 */
2603 static int convert_ctx_accesses(struct verifier_env *env)
2604 {
2605 struct bpf_insn *insn = env->prog->insnsi;
2606 int insn_cnt = env->prog->len;
2607 struct bpf_insn insn_buf[16];
2608 struct bpf_prog *new_prog;
2609 enum bpf_access_type type;
2610 int i;
2611
2612 if (!env->prog->aux->ops->convert_ctx_access)
2613 return 0;
2614
2615 for (i = 0; i < insn_cnt; i++, insn++) {
2616 u32 insn_delta, cnt;
2617
2618 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2619 type = BPF_READ;
2620 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2621 type = BPF_WRITE;
2622 else
2623 continue;
2624
2625 if (insn->imm != PTR_TO_CTX) {
2626 /* clear internal mark */
2627 insn->imm = 0;
2628 continue;
2629 }
2630
2631 cnt = env->prog->aux->ops->
2632 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
2633 insn->off, insn_buf, env->prog);
2634 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2635 verbose("bpf verifier is misconfigured\n");
2636 return -EINVAL;
2637 }
2638
2639 new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt);
2640 if (!new_prog)
2641 return -ENOMEM;
2642
2643 insn_delta = cnt - 1;
2644
2645 /* keep walking new program and skip insns we just inserted */
2646 env->prog = new_prog;
2647 insn = new_prog->insnsi + i + insn_delta;
2648
2649 insn_cnt += insn_delta;
2650 i += insn_delta;
2651 }
2652
2653 return 0;
2654 }
2655
2656 static void free_states(struct verifier_env *env)
2657 {
2658 struct verifier_state_list *sl, *sln;
2659 int i;
2660
2661 if (!env->explored_states)
2662 return;
2663
2664 for (i = 0; i < env->prog->len; i++) {
2665 sl = env->explored_states[i];
2666
2667 if (sl)
2668 while (sl != STATE_LIST_MARK) {
2669 sln = sl->next;
2670 kfree(sl);
2671 sl = sln;
2672 }
2673 }
2674
2675 kfree(env->explored_states);
2676 }
2677
2678 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
2679 {
2680 char __user *log_ubuf = NULL;
2681 struct verifier_env *env;
2682 int ret = -EINVAL;
2683
2684 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
2685 return -E2BIG;
2686
2687 /* 'struct verifier_env' can be global, but since it's not small,
2688 * allocate/free it every time bpf_check() is called
2689 */
2690 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2691 if (!env)
2692 return -ENOMEM;
2693
2694 env->prog = *prog;
2695
2696 /* grab the mutex to protect few globals used by verifier */
2697 mutex_lock(&bpf_verifier_lock);
2698
2699 if (attr->log_level || attr->log_buf || attr->log_size) {
2700 /* user requested verbose verifier output
2701 * and supplied buffer to store the verification trace
2702 */
2703 log_level = attr->log_level;
2704 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2705 log_size = attr->log_size;
2706 log_len = 0;
2707
2708 ret = -EINVAL;
2709 /* log_* values have to be sane */
2710 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2711 log_level == 0 || log_ubuf == NULL)
2712 goto free_env;
2713
2714 ret = -ENOMEM;
2715 log_buf = vmalloc(log_size);
2716 if (!log_buf)
2717 goto free_env;
2718 } else {
2719 log_level = 0;
2720 }
2721
2722 ret = replace_map_fd_with_map_ptr(env);
2723 if (ret < 0)
2724 goto skip_full_check;
2725
2726 env->explored_states = kcalloc(env->prog->len,
2727 sizeof(struct verifier_state_list *),
2728 GFP_USER);
2729 ret = -ENOMEM;
2730 if (!env->explored_states)
2731 goto skip_full_check;
2732
2733 ret = check_cfg(env);
2734 if (ret < 0)
2735 goto skip_full_check;
2736
2737 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2738
2739 ret = do_check(env);
2740
2741 skip_full_check:
2742 while (pop_stack(env, NULL) >= 0);
2743 free_states(env);
2744
2745 if (ret == 0)
2746 /* program is valid, convert *(u32*)(ctx + off) accesses */
2747 ret = convert_ctx_accesses(env);
2748
2749 if (log_level && log_len >= log_size - 1) {
2750 BUG_ON(log_len >= log_size);
2751 /* verifier log exceeded user supplied buffer */
2752 ret = -ENOSPC;
2753 /* fall through to return what was recorded */
2754 }
2755
2756 /* copy verifier log back to user space including trailing zero */
2757 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2758 ret = -EFAULT;
2759 goto free_log_buf;
2760 }
2761
2762 if (ret == 0 && env->used_map_cnt) {
2763 /* if program passed verifier, update used_maps in bpf_prog_info */
2764 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2765 sizeof(env->used_maps[0]),
2766 GFP_KERNEL);
2767
2768 if (!env->prog->aux->used_maps) {
2769 ret = -ENOMEM;
2770 goto free_log_buf;
2771 }
2772
2773 memcpy(env->prog->aux->used_maps, env->used_maps,
2774 sizeof(env->used_maps[0]) * env->used_map_cnt);
2775 env->prog->aux->used_map_cnt = env->used_map_cnt;
2776
2777 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2778 * bpf_ld_imm64 instructions
2779 */
2780 convert_pseudo_ld_imm64(env);
2781 }
2782
2783 free_log_buf:
2784 if (log_level)
2785 vfree(log_buf);
2786 free_env:
2787 if (!env->prog->aux->used_maps)
2788 /* if we didn't copy map pointers into bpf_prog_info, release
2789 * them now. Otherwise free_bpf_prog_info() will release them.
2790 */
2791 release_maps(env);
2792 *prog = env->prog;
2793 kfree(env);
2794 mutex_unlock(&bpf_verifier_lock);
2795 return ret;
2796 }
Linux kernel - Deliverables
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