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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/bpf_verifier.h>
18 #include <linux/filter.h>
19 #include <net/netlink.h>
20 #include <linux/file.h>
21 #include <linux/vmalloc.h>
22 #include <linux/stringify.h>
23
24 /* bpf_check() is a static code analyzer that walks eBPF program
25 * instruction by instruction and updates register/stack state.
26 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
27 *
28 * The first pass is depth-first-search to check that the program is a DAG.
29 * It rejects the following programs:
30 * - larger than BPF_MAXINSNS insns
31 * - if loop is present (detected via back-edge)
32 * - unreachable insns exist (shouldn't be a forest. program = one function)
33 * - out of bounds or malformed jumps
34 * The second pass is all possible path descent from the 1st insn.
35 * Since it's analyzing all pathes through the program, the length of the
36 * analysis is limited to 32k insn, which may be hit even if total number of
37 * insn is less then 4K, but there are too many branches that change stack/regs.
38 * Number of 'branches to be analyzed' is limited to 1k
39 *
40 * On entry to each instruction, each register has a type, and the instruction
41 * changes the types of the registers depending on instruction semantics.
42 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
43 * copied to R1.
44 *
45 * All registers are 64-bit.
46 * R0 - return register
47 * R1-R5 argument passing registers
48 * R6-R9 callee saved registers
49 * R10 - frame pointer read-only
50 *
51 * At the start of BPF program the register R1 contains a pointer to bpf_context
52 * and has type PTR_TO_CTX.
53 *
54 * Verifier tracks arithmetic operations on pointers in case:
55 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
56 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
57 * 1st insn copies R10 (which has FRAME_PTR) type into R1
58 * and 2nd arithmetic instruction is pattern matched to recognize
59 * that it wants to construct a pointer to some element within stack.
60 * So after 2nd insn, the register R1 has type PTR_TO_STACK
61 * (and -20 constant is saved for further stack bounds checking).
62 * Meaning that this reg is a pointer to stack plus known immediate constant.
63 *
64 * Most of the time the registers have UNKNOWN_VALUE type, which
65 * means the register has some value, but it's not a valid pointer.
66 * (like pointer plus pointer becomes UNKNOWN_VALUE type)
67 *
68 * When verifier sees load or store instructions the type of base register
69 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
70 * types recognized by check_mem_access() function.
71 *
72 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
73 * and the range of [ptr, ptr + map's value_size) is accessible.
74 *
75 * registers used to pass values to function calls are checked against
76 * function argument constraints.
77 *
78 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
79 * It means that the register type passed to this function must be
80 * PTR_TO_STACK and it will be used inside the function as
81 * 'pointer to map element key'
82 *
83 * For example the argument constraints for bpf_map_lookup_elem():
84 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
85 * .arg1_type = ARG_CONST_MAP_PTR,
86 * .arg2_type = ARG_PTR_TO_MAP_KEY,
87 *
88 * ret_type says that this function returns 'pointer to map elem value or null'
89 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
90 * 2nd argument should be a pointer to stack, which will be used inside
91 * the helper function as a pointer to map element key.
92 *
93 * On the kernel side the helper function looks like:
94 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
95 * {
96 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
97 * void *key = (void *) (unsigned long) r2;
98 * void *value;
99 *
100 * here kernel can access 'key' and 'map' pointers safely, knowing that
101 * [key, key + map->key_size) bytes are valid and were initialized on
102 * the stack of eBPF program.
103 * }
104 *
105 * Corresponding eBPF program may look like:
106 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
107 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
108 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
109 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
110 * here verifier looks at prototype of map_lookup_elem() and sees:
111 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
112 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
113 *
114 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
115 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
116 * and were initialized prior to this call.
117 * If it's ok, then verifier allows this BPF_CALL insn and looks at
118 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
119 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
120 * returns ether pointer to map value or NULL.
121 *
122 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
123 * insn, the register holding that pointer in the true branch changes state to
124 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
125 * branch. See check_cond_jmp_op().
126 *
127 * After the call R0 is set to return type of the function and registers R1-R5
128 * are set to NOT_INIT to indicate that they are no longer readable.
129 */
130
131 /* verifier_state + insn_idx are pushed to stack when branch is encountered */
132 struct bpf_verifier_stack_elem {
133 /* verifer state is 'st'
134 * before processing instruction 'insn_idx'
135 * and after processing instruction 'prev_insn_idx'
136 */
137 struct bpf_verifier_state st;
138 int insn_idx;
139 int prev_insn_idx;
140 struct bpf_verifier_stack_elem *next;
141 };
142
143 #define BPF_COMPLEXITY_LIMIT_INSNS 65536
144 #define BPF_COMPLEXITY_LIMIT_STACK 1024
145
146 struct bpf_call_arg_meta {
147 struct bpf_map *map_ptr;
148 bool raw_mode;
149 bool pkt_access;
150 int regno;
151 int access_size;
152 };
153
154 /* verbose verifier prints what it's seeing
155 * bpf_check() is called under lock, so no race to access these global vars
156 */
157 static u32 log_level, log_size, log_len;
158 static char *log_buf;
159
160 static DEFINE_MUTEX(bpf_verifier_lock);
161
162 /* log_level controls verbosity level of eBPF verifier.
163 * verbose() is used to dump the verification trace to the log, so the user
164 * can figure out what's wrong with the program
165 */
166 static __printf(1, 2) void verbose(const char *fmt, ...)
167 {
168 va_list args;
169
170 if (log_level == 0 || log_len >= log_size - 1)
171 return;
172
173 va_start(args, fmt);
174 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
175 va_end(args);
176 }
177
178 /* string representation of 'enum bpf_reg_type' */
179 static const char * const reg_type_str[] = {
180 [NOT_INIT] = "?",
181 [UNKNOWN_VALUE] = "inv",
182 [PTR_TO_CTX] = "ctx",
183 [CONST_PTR_TO_MAP] = "map_ptr",
184 [PTR_TO_MAP_VALUE] = "map_value",
185 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
186 [PTR_TO_MAP_VALUE_ADJ] = "map_value_adj",
187 [FRAME_PTR] = "fp",
188 [PTR_TO_STACK] = "fp",
189 [CONST_IMM] = "imm",
190 [PTR_TO_PACKET] = "pkt",
191 [PTR_TO_PACKET_END] = "pkt_end",
192 };
193
194 #define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x)
195 static const char * const func_id_str[] = {
196 __BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN)
197 };
198 #undef __BPF_FUNC_STR_FN
199
200 static const char *func_id_name(int id)
201 {
202 BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID);
203
204 if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id])
205 return func_id_str[id];
206 else
207 return "unknown";
208 }
209
210 static void print_verifier_state(struct bpf_verifier_state *state)
211 {
212 struct bpf_reg_state *reg;
213 enum bpf_reg_type t;
214 int i;
215
216 for (i = 0; i < MAX_BPF_REG; i++) {
217 reg = &state->regs[i];
218 t = reg->type;
219 if (t == NOT_INIT)
220 continue;
221 verbose(" R%d=%s", i, reg_type_str[t]);
222 if (t == CONST_IMM || t == PTR_TO_STACK)
223 verbose("%lld", reg->imm);
224 else if (t == PTR_TO_PACKET)
225 verbose("(id=%d,off=%d,r=%d)",
226 reg->id, reg->off, reg->range);
227 else if (t == UNKNOWN_VALUE && reg->imm)
228 verbose("%lld", reg->imm);
229 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
230 t == PTR_TO_MAP_VALUE_OR_NULL ||
231 t == PTR_TO_MAP_VALUE_ADJ)
232 verbose("(ks=%d,vs=%d,id=%u)",
233 reg->map_ptr->key_size,
234 reg->map_ptr->value_size,
235 reg->id);
236 if (reg->min_value != BPF_REGISTER_MIN_RANGE)
237 verbose(",min_value=%lld",
238 (long long)reg->min_value);
239 if (reg->max_value != BPF_REGISTER_MAX_RANGE)
240 verbose(",max_value=%llu",
241 (unsigned long long)reg->max_value);
242 }
243 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
244 if (state->stack_slot_type[i] == STACK_SPILL)
245 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
246 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]);
247 }
248 verbose("\n");
249 }
250
251 static const char *const bpf_class_string[] = {
252 [BPF_LD] = "ld",
253 [BPF_LDX] = "ldx",
254 [BPF_ST] = "st",
255 [BPF_STX] = "stx",
256 [BPF_ALU] = "alu",
257 [BPF_JMP] = "jmp",
258 [BPF_RET] = "BUG",
259 [BPF_ALU64] = "alu64",
260 };
261
262 static const char *const bpf_alu_string[16] = {
263 [BPF_ADD >> 4] = "+=",
264 [BPF_SUB >> 4] = "-=",
265 [BPF_MUL >> 4] = "*=",
266 [BPF_DIV >> 4] = "/=",
267 [BPF_OR >> 4] = "|=",
268 [BPF_AND >> 4] = "&=",
269 [BPF_LSH >> 4] = "<<=",
270 [BPF_RSH >> 4] = ">>=",
271 [BPF_NEG >> 4] = "neg",
272 [BPF_MOD >> 4] = "%=",
273 [BPF_XOR >> 4] = "^=",
274 [BPF_MOV >> 4] = "=",
275 [BPF_ARSH >> 4] = "s>>=",
276 [BPF_END >> 4] = "endian",
277 };
278
279 static const char *const bpf_ldst_string[] = {
280 [BPF_W >> 3] = "u32",
281 [BPF_H >> 3] = "u16",
282 [BPF_B >> 3] = "u8",
283 [BPF_DW >> 3] = "u64",
284 };
285
286 static const char *const bpf_jmp_string[16] = {
287 [BPF_JA >> 4] = "jmp",
288 [BPF_JEQ >> 4] = "==",
289 [BPF_JGT >> 4] = ">",
290 [BPF_JGE >> 4] = ">=",
291 [BPF_JSET >> 4] = "&",
292 [BPF_JNE >> 4] = "!=",
293 [BPF_JSGT >> 4] = "s>",
294 [BPF_JSGE >> 4] = "s>=",
295 [BPF_CALL >> 4] = "call",
296 [BPF_EXIT >> 4] = "exit",
297 };
298
299 static void print_bpf_insn(struct bpf_insn *insn)
300 {
301 u8 class = BPF_CLASS(insn->code);
302
303 if (class == BPF_ALU || class == BPF_ALU64) {
304 if (BPF_SRC(insn->code) == BPF_X)
305 verbose("(%02x) %sr%d %s %sr%d\n",
306 insn->code, class == BPF_ALU ? "(u32) " : "",
307 insn->dst_reg,
308 bpf_alu_string[BPF_OP(insn->code) >> 4],
309 class == BPF_ALU ? "(u32) " : "",
310 insn->src_reg);
311 else
312 verbose("(%02x) %sr%d %s %s%d\n",
313 insn->code, class == BPF_ALU ? "(u32) " : "",
314 insn->dst_reg,
315 bpf_alu_string[BPF_OP(insn->code) >> 4],
316 class == BPF_ALU ? "(u32) " : "",
317 insn->imm);
318 } else if (class == BPF_STX) {
319 if (BPF_MODE(insn->code) == BPF_MEM)
320 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
321 insn->code,
322 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
323 insn->dst_reg,
324 insn->off, insn->src_reg);
325 else if (BPF_MODE(insn->code) == BPF_XADD)
326 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
327 insn->code,
328 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
329 insn->dst_reg, insn->off,
330 insn->src_reg);
331 else
332 verbose("BUG_%02x\n", insn->code);
333 } else if (class == BPF_ST) {
334 if (BPF_MODE(insn->code) != BPF_MEM) {
335 verbose("BUG_st_%02x\n", insn->code);
336 return;
337 }
338 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
339 insn->code,
340 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
341 insn->dst_reg,
342 insn->off, insn->imm);
343 } else if (class == BPF_LDX) {
344 if (BPF_MODE(insn->code) != BPF_MEM) {
345 verbose("BUG_ldx_%02x\n", insn->code);
346 return;
347 }
348 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
349 insn->code, insn->dst_reg,
350 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
351 insn->src_reg, insn->off);
352 } else if (class == BPF_LD) {
353 if (BPF_MODE(insn->code) == BPF_ABS) {
354 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
355 insn->code,
356 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
357 insn->imm);
358 } else if (BPF_MODE(insn->code) == BPF_IND) {
359 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
360 insn->code,
361 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
362 insn->src_reg, insn->imm);
363 } else if (BPF_MODE(insn->code) == BPF_IMM) {
364 verbose("(%02x) r%d = 0x%x\n",
365 insn->code, insn->dst_reg, insn->imm);
366 } else {
367 verbose("BUG_ld_%02x\n", insn->code);
368 return;
369 }
370 } else if (class == BPF_JMP) {
371 u8 opcode = BPF_OP(insn->code);
372
373 if (opcode == BPF_CALL) {
374 verbose("(%02x) call %s#%d\n", insn->code,
375 func_id_name(insn->imm), insn->imm);
376 } else if (insn->code == (BPF_JMP | BPF_JA)) {
377 verbose("(%02x) goto pc%+d\n",
378 insn->code, insn->off);
379 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
380 verbose("(%02x) exit\n", insn->code);
381 } else if (BPF_SRC(insn->code) == BPF_X) {
382 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
383 insn->code, insn->dst_reg,
384 bpf_jmp_string[BPF_OP(insn->code) >> 4],
385 insn->src_reg, insn->off);
386 } else {
387 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
388 insn->code, insn->dst_reg,
389 bpf_jmp_string[BPF_OP(insn->code) >> 4],
390 insn->imm, insn->off);
391 }
392 } else {
393 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
394 }
395 }
396
397 static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx)
398 {
399 struct bpf_verifier_stack_elem *elem;
400 int insn_idx;
401
402 if (env->head == NULL)
403 return -1;
404
405 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
406 insn_idx = env->head->insn_idx;
407 if (prev_insn_idx)
408 *prev_insn_idx = env->head->prev_insn_idx;
409 elem = env->head->next;
410 kfree(env->head);
411 env->head = elem;
412 env->stack_size--;
413 return insn_idx;
414 }
415
416 static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
417 int insn_idx, int prev_insn_idx)
418 {
419 struct bpf_verifier_stack_elem *elem;
420
421 elem = kmalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
422 if (!elem)
423 goto err;
424
425 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
426 elem->insn_idx = insn_idx;
427 elem->prev_insn_idx = prev_insn_idx;
428 elem->next = env->head;
429 env->head = elem;
430 env->stack_size++;
431 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
432 verbose("BPF program is too complex\n");
433 goto err;
434 }
435 return &elem->st;
436 err:
437 /* pop all elements and return */
438 while (pop_stack(env, NULL) >= 0);
439 return NULL;
440 }
441
442 #define CALLER_SAVED_REGS 6
443 static const int caller_saved[CALLER_SAVED_REGS] = {
444 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
445 };
446
447 static void init_reg_state(struct bpf_reg_state *regs)
448 {
449 int i;
450
451 for (i = 0; i < MAX_BPF_REG; i++) {
452 regs[i].type = NOT_INIT;
453 regs[i].imm = 0;
454 regs[i].min_value = BPF_REGISTER_MIN_RANGE;
455 regs[i].max_value = BPF_REGISTER_MAX_RANGE;
456 }
457
458 /* frame pointer */
459 regs[BPF_REG_FP].type = FRAME_PTR;
460
461 /* 1st arg to a function */
462 regs[BPF_REG_1].type = PTR_TO_CTX;
463 }
464
465 static void mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno)
466 {
467 BUG_ON(regno >= MAX_BPF_REG);
468 regs[regno].type = UNKNOWN_VALUE;
469 regs[regno].id = 0;
470 regs[regno].imm = 0;
471 }
472
473 static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno)
474 {
475 regs[regno].min_value = BPF_REGISTER_MIN_RANGE;
476 regs[regno].max_value = BPF_REGISTER_MAX_RANGE;
477 }
478
479 enum reg_arg_type {
480 SRC_OP, /* register is used as source operand */
481 DST_OP, /* register is used as destination operand */
482 DST_OP_NO_MARK /* same as above, check only, don't mark */
483 };
484
485 static int check_reg_arg(struct bpf_reg_state *regs, u32 regno,
486 enum reg_arg_type t)
487 {
488 if (regno >= MAX_BPF_REG) {
489 verbose("R%d is invalid\n", regno);
490 return -EINVAL;
491 }
492
493 if (t == SRC_OP) {
494 /* check whether register used as source operand can be read */
495 if (regs[regno].type == NOT_INIT) {
496 verbose("R%d !read_ok\n", regno);
497 return -EACCES;
498 }
499 } else {
500 /* check whether register used as dest operand can be written to */
501 if (regno == BPF_REG_FP) {
502 verbose("frame pointer is read only\n");
503 return -EACCES;
504 }
505 if (t == DST_OP)
506 mark_reg_unknown_value(regs, regno);
507 }
508 return 0;
509 }
510
511 static int bpf_size_to_bytes(int bpf_size)
512 {
513 if (bpf_size == BPF_W)
514 return 4;
515 else if (bpf_size == BPF_H)
516 return 2;
517 else if (bpf_size == BPF_B)
518 return 1;
519 else if (bpf_size == BPF_DW)
520 return 8;
521 else
522 return -EINVAL;
523 }
524
525 static bool is_spillable_regtype(enum bpf_reg_type type)
526 {
527 switch (type) {
528 case PTR_TO_MAP_VALUE:
529 case PTR_TO_MAP_VALUE_OR_NULL:
530 case PTR_TO_STACK:
531 case PTR_TO_CTX:
532 case PTR_TO_PACKET:
533 case PTR_TO_PACKET_END:
534 case FRAME_PTR:
535 case CONST_PTR_TO_MAP:
536 return true;
537 default:
538 return false;
539 }
540 }
541
542 /* check_stack_read/write functions track spill/fill of registers,
543 * stack boundary and alignment are checked in check_mem_access()
544 */
545 static int check_stack_write(struct bpf_verifier_state *state, int off,
546 int size, int value_regno)
547 {
548 int i;
549 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
550 * so it's aligned access and [off, off + size) are within stack limits
551 */
552
553 if (value_regno >= 0 &&
554 is_spillable_regtype(state->regs[value_regno].type)) {
555
556 /* register containing pointer is being spilled into stack */
557 if (size != BPF_REG_SIZE) {
558 verbose("invalid size of register spill\n");
559 return -EACCES;
560 }
561
562 /* save register state */
563 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
564 state->regs[value_regno];
565
566 for (i = 0; i < BPF_REG_SIZE; i++)
567 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
568 } else {
569 /* regular write of data into stack */
570 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
571 (struct bpf_reg_state) {};
572
573 for (i = 0; i < size; i++)
574 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
575 }
576 return 0;
577 }
578
579 static int check_stack_read(struct bpf_verifier_state *state, int off, int size,
580 int value_regno)
581 {
582 u8 *slot_type;
583 int i;
584
585 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
586
587 if (slot_type[0] == STACK_SPILL) {
588 if (size != BPF_REG_SIZE) {
589 verbose("invalid size of register spill\n");
590 return -EACCES;
591 }
592 for (i = 1; i < BPF_REG_SIZE; i++) {
593 if (slot_type[i] != STACK_SPILL) {
594 verbose("corrupted spill memory\n");
595 return -EACCES;
596 }
597 }
598
599 if (value_regno >= 0)
600 /* restore register state from stack */
601 state->regs[value_regno] =
602 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
603 return 0;
604 } else {
605 for (i = 0; i < size; i++) {
606 if (slot_type[i] != STACK_MISC) {
607 verbose("invalid read from stack off %d+%d size %d\n",
608 off, i, size);
609 return -EACCES;
610 }
611 }
612 if (value_regno >= 0)
613 /* have read misc data from the stack */
614 mark_reg_unknown_value(state->regs, value_regno);
615 return 0;
616 }
617 }
618
619 /* check read/write into map element returned by bpf_map_lookup_elem() */
620 static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
621 int size)
622 {
623 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
624
625 if (off < 0 || off + size > map->value_size) {
626 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
627 map->value_size, off, size);
628 return -EACCES;
629 }
630 return 0;
631 }
632
633 #define MAX_PACKET_OFF 0xffff
634
635 static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
636 const struct bpf_call_arg_meta *meta,
637 enum bpf_access_type t)
638 {
639 switch (env->prog->type) {
640 case BPF_PROG_TYPE_LWT_IN:
641 case BPF_PROG_TYPE_LWT_OUT:
642 /* dst_input() and dst_output() can't write for now */
643 if (t == BPF_WRITE)
644 return false;
645 case BPF_PROG_TYPE_SCHED_CLS:
646 case BPF_PROG_TYPE_SCHED_ACT:
647 case BPF_PROG_TYPE_XDP:
648 case BPF_PROG_TYPE_LWT_XMIT:
649 if (meta)
650 return meta->pkt_access;
651
652 env->seen_direct_write = true;
653 return true;
654 default:
655 return false;
656 }
657 }
658
659 static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
660 int size)
661 {
662 struct bpf_reg_state *regs = env->cur_state.regs;
663 struct bpf_reg_state *reg = &regs[regno];
664
665 off += reg->off;
666 if (off < 0 || size <= 0 || off + size > reg->range) {
667 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
668 off, size, regno, reg->id, reg->off, reg->range);
669 return -EACCES;
670 }
671 return 0;
672 }
673
674 /* check access to 'struct bpf_context' fields */
675 static int check_ctx_access(struct bpf_verifier_env *env, int off, int size,
676 enum bpf_access_type t, enum bpf_reg_type *reg_type)
677 {
678 /* for analyzer ctx accesses are already validated and converted */
679 if (env->analyzer_ops)
680 return 0;
681
682 if (env->prog->aux->ops->is_valid_access &&
683 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) {
684 /* remember the offset of last byte accessed in ctx */
685 if (env->prog->aux->max_ctx_offset < off + size)
686 env->prog->aux->max_ctx_offset = off + size;
687 return 0;
688 }
689
690 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
691 return -EACCES;
692 }
693
694 static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
695 {
696 if (env->allow_ptr_leaks)
697 return false;
698
699 switch (env->cur_state.regs[regno].type) {
700 case UNKNOWN_VALUE:
701 case CONST_IMM:
702 return false;
703 default:
704 return true;
705 }
706 }
707
708 static int check_ptr_alignment(struct bpf_verifier_env *env,
709 struct bpf_reg_state *reg, int off, int size)
710 {
711 if (reg->type != PTR_TO_PACKET && reg->type != PTR_TO_MAP_VALUE_ADJ) {
712 if (off % size != 0) {
713 verbose("misaligned access off %d size %d\n",
714 off, size);
715 return -EACCES;
716 } else {
717 return 0;
718 }
719 }
720
721 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
722 /* misaligned access to packet is ok on x86,arm,arm64 */
723 return 0;
724
725 if (reg->id && size != 1) {
726 verbose("Unknown packet alignment. Only byte-sized access allowed\n");
727 return -EACCES;
728 }
729
730 /* skb->data is NET_IP_ALIGN-ed */
731 if (reg->type == PTR_TO_PACKET &&
732 (NET_IP_ALIGN + reg->off + off) % size != 0) {
733 verbose("misaligned packet access off %d+%d+%d size %d\n",
734 NET_IP_ALIGN, reg->off, off, size);
735 return -EACCES;
736 }
737 return 0;
738 }
739
740 /* check whether memory at (regno + off) is accessible for t = (read | write)
741 * if t==write, value_regno is a register which value is stored into memory
742 * if t==read, value_regno is a register which will receive the value from memory
743 * if t==write && value_regno==-1, some unknown value is stored into memory
744 * if t==read && value_regno==-1, don't care what we read from memory
745 */
746 static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off,
747 int bpf_size, enum bpf_access_type t,
748 int value_regno)
749 {
750 struct bpf_verifier_state *state = &env->cur_state;
751 struct bpf_reg_state *reg = &state->regs[regno];
752 int size, err = 0;
753
754 if (reg->type == PTR_TO_STACK)
755 off += reg->imm;
756
757 size = bpf_size_to_bytes(bpf_size);
758 if (size < 0)
759 return size;
760
761 err = check_ptr_alignment(env, reg, off, size);
762 if (err)
763 return err;
764
765 if (reg->type == PTR_TO_MAP_VALUE ||
766 reg->type == PTR_TO_MAP_VALUE_ADJ) {
767 if (t == BPF_WRITE && value_regno >= 0 &&
768 is_pointer_value(env, value_regno)) {
769 verbose("R%d leaks addr into map\n", value_regno);
770 return -EACCES;
771 }
772
773 /* If we adjusted the register to this map value at all then we
774 * need to change off and size to min_value and max_value
775 * respectively to make sure our theoretical access will be
776 * safe.
777 */
778 if (reg->type == PTR_TO_MAP_VALUE_ADJ) {
779 if (log_level)
780 print_verifier_state(state);
781 env->varlen_map_value_access = true;
782 /* The minimum value is only important with signed
783 * comparisons where we can't assume the floor of a
784 * value is 0. If we are using signed variables for our
785 * index'es we need to make sure that whatever we use
786 * will have a set floor within our range.
787 */
788 if (reg->min_value < 0) {
789 verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
790 regno);
791 return -EACCES;
792 }
793 err = check_map_access(env, regno, reg->min_value + off,
794 size);
795 if (err) {
796 verbose("R%d min value is outside of the array range\n",
797 regno);
798 return err;
799 }
800
801 /* If we haven't set a max value then we need to bail
802 * since we can't be sure we won't do bad things.
803 */
804 if (reg->max_value == BPF_REGISTER_MAX_RANGE) {
805 verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n",
806 regno);
807 return -EACCES;
808 }
809 off += reg->max_value;
810 }
811 err = check_map_access(env, regno, off, size);
812 if (!err && t == BPF_READ && value_regno >= 0)
813 mark_reg_unknown_value(state->regs, value_regno);
814
815 } else if (reg->type == PTR_TO_CTX) {
816 enum bpf_reg_type reg_type = UNKNOWN_VALUE;
817
818 if (t == BPF_WRITE && value_regno >= 0 &&
819 is_pointer_value(env, value_regno)) {
820 verbose("R%d leaks addr into ctx\n", value_regno);
821 return -EACCES;
822 }
823 err = check_ctx_access(env, off, size, t, &reg_type);
824 if (!err && t == BPF_READ && value_regno >= 0) {
825 mark_reg_unknown_value(state->regs, value_regno);
826 /* note that reg.[id|off|range] == 0 */
827 state->regs[value_regno].type = reg_type;
828 }
829
830 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {
831 if (off >= 0 || off < -MAX_BPF_STACK) {
832 verbose("invalid stack off=%d size=%d\n", off, size);
833 return -EACCES;
834 }
835 if (t == BPF_WRITE) {
836 if (!env->allow_ptr_leaks &&
837 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
838 size != BPF_REG_SIZE) {
839 verbose("attempt to corrupt spilled pointer on stack\n");
840 return -EACCES;
841 }
842 err = check_stack_write(state, off, size, value_regno);
843 } else {
844 err = check_stack_read(state, off, size, value_regno);
845 }
846 } else if (state->regs[regno].type == PTR_TO_PACKET) {
847 if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) {
848 verbose("cannot write into packet\n");
849 return -EACCES;
850 }
851 if (t == BPF_WRITE && value_regno >= 0 &&
852 is_pointer_value(env, value_regno)) {
853 verbose("R%d leaks addr into packet\n", value_regno);
854 return -EACCES;
855 }
856 err = check_packet_access(env, regno, off, size);
857 if (!err && t == BPF_READ && value_regno >= 0)
858 mark_reg_unknown_value(state->regs, value_regno);
859 } else {
860 verbose("R%d invalid mem access '%s'\n",
861 regno, reg_type_str[reg->type]);
862 return -EACCES;
863 }
864
865 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks &&
866 state->regs[value_regno].type == UNKNOWN_VALUE) {
867 /* 1 or 2 byte load zero-extends, determine the number of
868 * zero upper bits. Not doing it fo 4 byte load, since
869 * such values cannot be added to ptr_to_packet anyway.
870 */
871 state->regs[value_regno].imm = 64 - size * 8;
872 }
873 return err;
874 }
875
876 static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn)
877 {
878 struct bpf_reg_state *regs = env->cur_state.regs;
879 int err;
880
881 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
882 insn->imm != 0) {
883 verbose("BPF_XADD uses reserved fields\n");
884 return -EINVAL;
885 }
886
887 /* check src1 operand */
888 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
889 if (err)
890 return err;
891
892 /* check src2 operand */
893 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
894 if (err)
895 return err;
896
897 /* check whether atomic_add can read the memory */
898 err = check_mem_access(env, insn->dst_reg, insn->off,
899 BPF_SIZE(insn->code), BPF_READ, -1);
900 if (err)
901 return err;
902
903 /* check whether atomic_add can write into the same memory */
904 return check_mem_access(env, insn->dst_reg, insn->off,
905 BPF_SIZE(insn->code), BPF_WRITE, -1);
906 }
907
908 /* when register 'regno' is passed into function that will read 'access_size'
909 * bytes from that pointer, make sure that it's within stack boundary
910 * and all elements of stack are initialized
911 */
912 static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
913 int access_size, bool zero_size_allowed,
914 struct bpf_call_arg_meta *meta)
915 {
916 struct bpf_verifier_state *state = &env->cur_state;
917 struct bpf_reg_state *regs = state->regs;
918 int off, i;
919
920 if (regs[regno].type != PTR_TO_STACK) {
921 if (zero_size_allowed && access_size == 0 &&
922 regs[regno].type == CONST_IMM &&
923 regs[regno].imm == 0)
924 return 0;
925
926 verbose("R%d type=%s expected=%s\n", regno,
927 reg_type_str[regs[regno].type],
928 reg_type_str[PTR_TO_STACK]);
929 return -EACCES;
930 }
931
932 off = regs[regno].imm;
933 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
934 access_size <= 0) {
935 verbose("invalid stack type R%d off=%d access_size=%d\n",
936 regno, off, access_size);
937 return -EACCES;
938 }
939
940 if (meta && meta->raw_mode) {
941 meta->access_size = access_size;
942 meta->regno = regno;
943 return 0;
944 }
945
946 for (i = 0; i < access_size; i++) {
947 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
948 verbose("invalid indirect read from stack off %d+%d size %d\n",
949 off, i, access_size);
950 return -EACCES;
951 }
952 }
953 return 0;
954 }
955
956 static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
957 enum bpf_arg_type arg_type,
958 struct bpf_call_arg_meta *meta)
959 {
960 struct bpf_reg_state *regs = env->cur_state.regs, *reg = &regs[regno];
961 enum bpf_reg_type expected_type, type = reg->type;
962 int err = 0;
963
964 if (arg_type == ARG_DONTCARE)
965 return 0;
966
967 if (type == NOT_INIT) {
968 verbose("R%d !read_ok\n", regno);
969 return -EACCES;
970 }
971
972 if (arg_type == ARG_ANYTHING) {
973 if (is_pointer_value(env, regno)) {
974 verbose("R%d leaks addr into helper function\n", regno);
975 return -EACCES;
976 }
977 return 0;
978 }
979
980 if (type == PTR_TO_PACKET &&
981 !may_access_direct_pkt_data(env, meta, BPF_READ)) {
982 verbose("helper access to the packet is not allowed\n");
983 return -EACCES;
984 }
985
986 if (arg_type == ARG_PTR_TO_MAP_KEY ||
987 arg_type == ARG_PTR_TO_MAP_VALUE) {
988 expected_type = PTR_TO_STACK;
989 if (type != PTR_TO_PACKET && type != expected_type)
990 goto err_type;
991 } else if (arg_type == ARG_CONST_STACK_SIZE ||
992 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
993 expected_type = CONST_IMM;
994 if (type != expected_type)
995 goto err_type;
996 } else if (arg_type == ARG_CONST_MAP_PTR) {
997 expected_type = CONST_PTR_TO_MAP;
998 if (type != expected_type)
999 goto err_type;
1000 } else if (arg_type == ARG_PTR_TO_CTX) {
1001 expected_type = PTR_TO_CTX;
1002 if (type != expected_type)
1003 goto err_type;
1004 } else if (arg_type == ARG_PTR_TO_STACK ||
1005 arg_type == ARG_PTR_TO_RAW_STACK) {
1006 expected_type = PTR_TO_STACK;
1007 /* One exception here. In case function allows for NULL to be
1008 * passed in as argument, it's a CONST_IMM type. Final test
1009 * happens during stack boundary checking.
1010 */
1011 if (type == CONST_IMM && reg->imm == 0)
1012 /* final test in check_stack_boundary() */;
1013 else if (type != PTR_TO_PACKET && type != expected_type)
1014 goto err_type;
1015 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK;
1016 } else {
1017 verbose("unsupported arg_type %d\n", arg_type);
1018 return -EFAULT;
1019 }
1020
1021 if (arg_type == ARG_CONST_MAP_PTR) {
1022 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
1023 meta->map_ptr = reg->map_ptr;
1024 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
1025 /* bpf_map_xxx(..., map_ptr, ..., key) call:
1026 * check that [key, key + map->key_size) are within
1027 * stack limits and initialized
1028 */
1029 if (!meta->map_ptr) {
1030 /* in function declaration map_ptr must come before
1031 * map_key, so that it's verified and known before
1032 * we have to check map_key here. Otherwise it means
1033 * that kernel subsystem misconfigured verifier
1034 */
1035 verbose("invalid map_ptr to access map->key\n");
1036 return -EACCES;
1037 }
1038 if (type == PTR_TO_PACKET)
1039 err = check_packet_access(env, regno, 0,
1040 meta->map_ptr->key_size);
1041 else
1042 err = check_stack_boundary(env, regno,
1043 meta->map_ptr->key_size,
1044 false, NULL);
1045 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
1046 /* bpf_map_xxx(..., map_ptr, ..., value) call:
1047 * check [value, value + map->value_size) validity
1048 */
1049 if (!meta->map_ptr) {
1050 /* kernel subsystem misconfigured verifier */
1051 verbose("invalid map_ptr to access map->value\n");
1052 return -EACCES;
1053 }
1054 if (type == PTR_TO_PACKET)
1055 err = check_packet_access(env, regno, 0,
1056 meta->map_ptr->value_size);
1057 else
1058 err = check_stack_boundary(env, regno,
1059 meta->map_ptr->value_size,
1060 false, NULL);
1061 } else if (arg_type == ARG_CONST_STACK_SIZE ||
1062 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
1063 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
1064
1065 /* bpf_xxx(..., buf, len) call will access 'len' bytes
1066 * from stack pointer 'buf'. Check it
1067 * note: regno == len, regno - 1 == buf
1068 */
1069 if (regno == 0) {
1070 /* kernel subsystem misconfigured verifier */
1071 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
1072 return -EACCES;
1073 }
1074 if (regs[regno - 1].type == PTR_TO_PACKET)
1075 err = check_packet_access(env, regno - 1, 0, reg->imm);
1076 else
1077 err = check_stack_boundary(env, regno - 1, reg->imm,
1078 zero_size_allowed, meta);
1079 }
1080
1081 return err;
1082 err_type:
1083 verbose("R%d type=%s expected=%s\n", regno,
1084 reg_type_str[type], reg_type_str[expected_type]);
1085 return -EACCES;
1086 }
1087
1088 static int check_map_func_compatibility(struct bpf_map *map, int func_id)
1089 {
1090 if (!map)
1091 return 0;
1092
1093 /* We need a two way check, first is from map perspective ... */
1094 switch (map->map_type) {
1095 case BPF_MAP_TYPE_PROG_ARRAY:
1096 if (func_id != BPF_FUNC_tail_call)
1097 goto error;
1098 break;
1099 case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
1100 if (func_id != BPF_FUNC_perf_event_read &&
1101 func_id != BPF_FUNC_perf_event_output)
1102 goto error;
1103 break;
1104 case BPF_MAP_TYPE_STACK_TRACE:
1105 if (func_id != BPF_FUNC_get_stackid)
1106 goto error;
1107 break;
1108 case BPF_MAP_TYPE_CGROUP_ARRAY:
1109 if (func_id != BPF_FUNC_skb_under_cgroup &&
1110 func_id != BPF_FUNC_current_task_under_cgroup)
1111 goto error;
1112 break;
1113 default:
1114 break;
1115 }
1116
1117 /* ... and second from the function itself. */
1118 switch (func_id) {
1119 case BPF_FUNC_tail_call:
1120 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
1121 goto error;
1122 break;
1123 case BPF_FUNC_perf_event_read:
1124 case BPF_FUNC_perf_event_output:
1125 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
1126 goto error;
1127 break;
1128 case BPF_FUNC_get_stackid:
1129 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
1130 goto error;
1131 break;
1132 case BPF_FUNC_current_task_under_cgroup:
1133 case BPF_FUNC_skb_under_cgroup:
1134 if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
1135 goto error;
1136 break;
1137 default:
1138 break;
1139 }
1140
1141 return 0;
1142 error:
1143 verbose("cannot pass map_type %d into func %s#%d\n",
1144 map->map_type, func_id_name(func_id), func_id);
1145 return -EINVAL;
1146 }
1147
1148 static int check_raw_mode(const struct bpf_func_proto *fn)
1149 {
1150 int count = 0;
1151
1152 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK)
1153 count++;
1154 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK)
1155 count++;
1156 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK)
1157 count++;
1158 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK)
1159 count++;
1160 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK)
1161 count++;
1162
1163 return count > 1 ? -EINVAL : 0;
1164 }
1165
1166 static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
1167 {
1168 struct bpf_verifier_state *state = &env->cur_state;
1169 struct bpf_reg_state *regs = state->regs, *reg;
1170 int i;
1171
1172 for (i = 0; i < MAX_BPF_REG; i++)
1173 if (regs[i].type == PTR_TO_PACKET ||
1174 regs[i].type == PTR_TO_PACKET_END)
1175 mark_reg_unknown_value(regs, i);
1176
1177 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1178 if (state->stack_slot_type[i] != STACK_SPILL)
1179 continue;
1180 reg = &state->spilled_regs[i / BPF_REG_SIZE];
1181 if (reg->type != PTR_TO_PACKET &&
1182 reg->type != PTR_TO_PACKET_END)
1183 continue;
1184 reg->type = UNKNOWN_VALUE;
1185 reg->imm = 0;
1186 }
1187 }
1188
1189 static int check_call(struct bpf_verifier_env *env, int func_id)
1190 {
1191 struct bpf_verifier_state *state = &env->cur_state;
1192 const struct bpf_func_proto *fn = NULL;
1193 struct bpf_reg_state *regs = state->regs;
1194 struct bpf_reg_state *reg;
1195 struct bpf_call_arg_meta meta;
1196 bool changes_data;
1197 int i, err;
1198
1199 /* find function prototype */
1200 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
1201 verbose("invalid func %s#%d\n", func_id_name(func_id), func_id);
1202 return -EINVAL;
1203 }
1204
1205 if (env->prog->aux->ops->get_func_proto)
1206 fn = env->prog->aux->ops->get_func_proto(func_id);
1207
1208 if (!fn) {
1209 verbose("unknown func %s#%d\n", func_id_name(func_id), func_id);
1210 return -EINVAL;
1211 }
1212
1213 /* eBPF programs must be GPL compatible to use GPL-ed functions */
1214 if (!env->prog->gpl_compatible && fn->gpl_only) {
1215 verbose("cannot call GPL only function from proprietary program\n");
1216 return -EINVAL;
1217 }
1218
1219 changes_data = bpf_helper_changes_skb_data(fn->func);
1220
1221 memset(&meta, 0, sizeof(meta));
1222 meta.pkt_access = fn->pkt_access;
1223
1224 /* We only support one arg being in raw mode at the moment, which
1225 * is sufficient for the helper functions we have right now.
1226 */
1227 err = check_raw_mode(fn);
1228 if (err) {
1229 verbose("kernel subsystem misconfigured func %s#%d\n",
1230 func_id_name(func_id), func_id);
1231 return err;
1232 }
1233
1234 /* check args */
1235 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
1236 if (err)
1237 return err;
1238 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
1239 if (err)
1240 return err;
1241 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
1242 if (err)
1243 return err;
1244 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
1245 if (err)
1246 return err;
1247 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
1248 if (err)
1249 return err;
1250
1251 /* Mark slots with STACK_MISC in case of raw mode, stack offset
1252 * is inferred from register state.
1253 */
1254 for (i = 0; i < meta.access_size; i++) {
1255 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1);
1256 if (err)
1257 return err;
1258 }
1259
1260 /* reset caller saved regs */
1261 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1262 reg = regs + caller_saved[i];
1263 reg->type = NOT_INIT;
1264 reg->imm = 0;
1265 }
1266
1267 /* update return register */
1268 if (fn->ret_type == RET_INTEGER) {
1269 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1270 } else if (fn->ret_type == RET_VOID) {
1271 regs[BPF_REG_0].type = NOT_INIT;
1272 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
1273 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
1274 regs[BPF_REG_0].max_value = regs[BPF_REG_0].min_value = 0;
1275 /* remember map_ptr, so that check_map_access()
1276 * can check 'value_size' boundary of memory access
1277 * to map element returned from bpf_map_lookup_elem()
1278 */
1279 if (meta.map_ptr == NULL) {
1280 verbose("kernel subsystem misconfigured verifier\n");
1281 return -EINVAL;
1282 }
1283 regs[BPF_REG_0].map_ptr = meta.map_ptr;
1284 regs[BPF_REG_0].id = ++env->id_gen;
1285 } else {
1286 verbose("unknown return type %d of func %s#%d\n",
1287 fn->ret_type, func_id_name(func_id), func_id);
1288 return -EINVAL;
1289 }
1290
1291 err = check_map_func_compatibility(meta.map_ptr, func_id);
1292 if (err)
1293 return err;
1294
1295 if (changes_data)
1296 clear_all_pkt_pointers(env);
1297 return 0;
1298 }
1299
1300 static int check_packet_ptr_add(struct bpf_verifier_env *env,
1301 struct bpf_insn *insn)
1302 {
1303 struct bpf_reg_state *regs = env->cur_state.regs;
1304 struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
1305 struct bpf_reg_state *src_reg = &regs[insn->src_reg];
1306 struct bpf_reg_state tmp_reg;
1307 s32 imm;
1308
1309 if (BPF_SRC(insn->code) == BPF_K) {
1310 /* pkt_ptr += imm */
1311 imm = insn->imm;
1312
1313 add_imm:
1314 if (imm <= 0) {
1315 verbose("addition of negative constant to packet pointer is not allowed\n");
1316 return -EACCES;
1317 }
1318 if (imm >= MAX_PACKET_OFF ||
1319 imm + dst_reg->off >= MAX_PACKET_OFF) {
1320 verbose("constant %d is too large to add to packet pointer\n",
1321 imm);
1322 return -EACCES;
1323 }
1324 /* a constant was added to pkt_ptr.
1325 * Remember it while keeping the same 'id'
1326 */
1327 dst_reg->off += imm;
1328 } else {
1329 if (src_reg->type == PTR_TO_PACKET) {
1330 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */
1331 tmp_reg = *dst_reg; /* save r7 state */
1332 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */
1333 src_reg = &tmp_reg; /* pretend it's src_reg state */
1334 /* if the checks below reject it, the copy won't matter,
1335 * since we're rejecting the whole program. If all ok,
1336 * then imm22 state will be added to r7
1337 * and r7 will be pkt(id=0,off=22,r=62) while
1338 * r6 will stay as pkt(id=0,off=0,r=62)
1339 */
1340 }
1341
1342 if (src_reg->type == CONST_IMM) {
1343 /* pkt_ptr += reg where reg is known constant */
1344 imm = src_reg->imm;
1345 goto add_imm;
1346 }
1347 /* disallow pkt_ptr += reg
1348 * if reg is not uknown_value with guaranteed zero upper bits
1349 * otherwise pkt_ptr may overflow and addition will become
1350 * subtraction which is not allowed
1351 */
1352 if (src_reg->type != UNKNOWN_VALUE) {
1353 verbose("cannot add '%s' to ptr_to_packet\n",
1354 reg_type_str[src_reg->type]);
1355 return -EACCES;
1356 }
1357 if (src_reg->imm < 48) {
1358 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n",
1359 src_reg->imm);
1360 return -EACCES;
1361 }
1362 /* dst_reg stays as pkt_ptr type and since some positive
1363 * integer value was added to the pointer, increment its 'id'
1364 */
1365 dst_reg->id = ++env->id_gen;
1366
1367 /* something was added to pkt_ptr, set range and off to zero */
1368 dst_reg->off = 0;
1369 dst_reg->range = 0;
1370 }
1371 return 0;
1372 }
1373
1374 static int evaluate_reg_alu(struct bpf_verifier_env *env, struct bpf_insn *insn)
1375 {
1376 struct bpf_reg_state *regs = env->cur_state.regs;
1377 struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
1378 u8 opcode = BPF_OP(insn->code);
1379 s64 imm_log2;
1380
1381 /* for type == UNKNOWN_VALUE:
1382 * imm > 0 -> number of zero upper bits
1383 * imm == 0 -> don't track which is the same as all bits can be non-zero
1384 */
1385
1386 if (BPF_SRC(insn->code) == BPF_X) {
1387 struct bpf_reg_state *src_reg = &regs[insn->src_reg];
1388
1389 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 &&
1390 dst_reg->imm && opcode == BPF_ADD) {
1391 /* dreg += sreg
1392 * where both have zero upper bits. Adding them
1393 * can only result making one more bit non-zero
1394 * in the larger value.
1395 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47)
1396 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47)
1397 */
1398 dst_reg->imm = min(dst_reg->imm, src_reg->imm);
1399 dst_reg->imm--;
1400 return 0;
1401 }
1402 if (src_reg->type == CONST_IMM && src_reg->imm > 0 &&
1403 dst_reg->imm && opcode == BPF_ADD) {
1404 /* dreg += sreg
1405 * where dreg has zero upper bits and sreg is const.
1406 * Adding them can only result making one more bit
1407 * non-zero in the larger value.
1408 */
1409 imm_log2 = __ilog2_u64((long long)src_reg->imm);
1410 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
1411 dst_reg->imm--;
1412 return 0;
1413 }
1414 /* all other cases non supported yet, just mark dst_reg */
1415 dst_reg->imm = 0;
1416 return 0;
1417 }
1418
1419 /* sign extend 32-bit imm into 64-bit to make sure that
1420 * negative values occupy bit 63. Note ilog2() would have
1421 * been incorrect, since sizeof(insn->imm) == 4
1422 */
1423 imm_log2 = __ilog2_u64((long long)insn->imm);
1424
1425 if (dst_reg->imm && opcode == BPF_LSH) {
1426 /* reg <<= imm
1427 * if reg was a result of 2 byte load, then its imm == 48
1428 * which means that upper 48 bits are zero and shifting this reg
1429 * left by 4 would mean that upper 44 bits are still zero
1430 */
1431 dst_reg->imm -= insn->imm;
1432 } else if (dst_reg->imm && opcode == BPF_MUL) {
1433 /* reg *= imm
1434 * if multiplying by 14 subtract 4
1435 * This is conservative calculation of upper zero bits.
1436 * It's not trying to special case insn->imm == 1 or 0 cases
1437 */
1438 dst_reg->imm -= imm_log2 + 1;
1439 } else if (opcode == BPF_AND) {
1440 /* reg &= imm */
1441 dst_reg->imm = 63 - imm_log2;
1442 } else if (dst_reg->imm && opcode == BPF_ADD) {
1443 /* reg += imm */
1444 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
1445 dst_reg->imm--;
1446 } else if (opcode == BPF_RSH) {
1447 /* reg >>= imm
1448 * which means that after right shift, upper bits will be zero
1449 * note that verifier already checked that
1450 * 0 <= imm < 64 for shift insn
1451 */
1452 dst_reg->imm += insn->imm;
1453 if (unlikely(dst_reg->imm > 64))
1454 /* some dumb code did:
1455 * r2 = *(u32 *)mem;
1456 * r2 >>= 32;
1457 * and all bits are zero now */
1458 dst_reg->imm = 64;
1459 } else {
1460 /* all other alu ops, means that we don't know what will
1461 * happen to the value, mark it with unknown number of zero bits
1462 */
1463 dst_reg->imm = 0;
1464 }
1465
1466 if (dst_reg->imm < 0) {
1467 /* all 64 bits of the register can contain non-zero bits
1468 * and such value cannot be added to ptr_to_packet, since it
1469 * may overflow, mark it as unknown to avoid further eval
1470 */
1471 dst_reg->imm = 0;
1472 }
1473 return 0;
1474 }
1475
1476 static int evaluate_reg_imm_alu(struct bpf_verifier_env *env,
1477 struct bpf_insn *insn)
1478 {
1479 struct bpf_reg_state *regs = env->cur_state.regs;
1480 struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
1481 struct bpf_reg_state *src_reg = &regs[insn->src_reg];
1482 u8 opcode = BPF_OP(insn->code);
1483
1484 /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn.
1485 * Don't care about overflow or negative values, just add them
1486 */
1487 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K)
1488 dst_reg->imm += insn->imm;
1489 else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X &&
1490 src_reg->type == CONST_IMM)
1491 dst_reg->imm += src_reg->imm;
1492 else
1493 mark_reg_unknown_value(regs, insn->dst_reg);
1494 return 0;
1495 }
1496
1497 static void check_reg_overflow(struct bpf_reg_state *reg)
1498 {
1499 if (reg->max_value > BPF_REGISTER_MAX_RANGE)
1500 reg->max_value = BPF_REGISTER_MAX_RANGE;
1501 if (reg->min_value < BPF_REGISTER_MIN_RANGE ||
1502 reg->min_value > BPF_REGISTER_MAX_RANGE)
1503 reg->min_value = BPF_REGISTER_MIN_RANGE;
1504 }
1505
1506 static void adjust_reg_min_max_vals(struct bpf_verifier_env *env,
1507 struct bpf_insn *insn)
1508 {
1509 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg;
1510 s64 min_val = BPF_REGISTER_MIN_RANGE;
1511 u64 max_val = BPF_REGISTER_MAX_RANGE;
1512 u8 opcode = BPF_OP(insn->code);
1513
1514 dst_reg = &regs[insn->dst_reg];
1515 if (BPF_SRC(insn->code) == BPF_X) {
1516 check_reg_overflow(&regs[insn->src_reg]);
1517 min_val = regs[insn->src_reg].min_value;
1518 max_val = regs[insn->src_reg].max_value;
1519
1520 /* If the source register is a random pointer then the
1521 * min_value/max_value values represent the range of the known
1522 * accesses into that value, not the actual min/max value of the
1523 * register itself. In this case we have to reset the reg range
1524 * values so we know it is not safe to look at.
1525 */
1526 if (regs[insn->src_reg].type != CONST_IMM &&
1527 regs[insn->src_reg].type != UNKNOWN_VALUE) {
1528 min_val = BPF_REGISTER_MIN_RANGE;
1529 max_val = BPF_REGISTER_MAX_RANGE;
1530 }
1531 } else if (insn->imm < BPF_REGISTER_MAX_RANGE &&
1532 (s64)insn->imm > BPF_REGISTER_MIN_RANGE) {
1533 min_val = max_val = insn->imm;
1534 }
1535
1536 /* We don't know anything about what was done to this register, mark it
1537 * as unknown.
1538 */
1539 if (min_val == BPF_REGISTER_MIN_RANGE &&
1540 max_val == BPF_REGISTER_MAX_RANGE) {
1541 reset_reg_range_values(regs, insn->dst_reg);
1542 return;
1543 }
1544
1545 /* If one of our values was at the end of our ranges then we can't just
1546 * do our normal operations to the register, we need to set the values
1547 * to the min/max since they are undefined.
1548 */
1549 if (min_val == BPF_REGISTER_MIN_RANGE)
1550 dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
1551 if (max_val == BPF_REGISTER_MAX_RANGE)
1552 dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
1553
1554 switch (opcode) {
1555 case BPF_ADD:
1556 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
1557 dst_reg->min_value += min_val;
1558 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
1559 dst_reg->max_value += max_val;
1560 break;
1561 case BPF_SUB:
1562 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
1563 dst_reg->min_value -= min_val;
1564 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
1565 dst_reg->max_value -= max_val;
1566 break;
1567 case BPF_MUL:
1568 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
1569 dst_reg->min_value *= min_val;
1570 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
1571 dst_reg->max_value *= max_val;
1572 break;
1573 case BPF_AND:
1574 /* Disallow AND'ing of negative numbers, ain't nobody got time
1575 * for that. Otherwise the minimum is 0 and the max is the max
1576 * value we could AND against.
1577 */
1578 if (min_val < 0)
1579 dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
1580 else
1581 dst_reg->min_value = 0;
1582 dst_reg->max_value = max_val;
1583 break;
1584 case BPF_LSH:
1585 /* Gotta have special overflow logic here, if we're shifting
1586 * more than MAX_RANGE then just assume we have an invalid
1587 * range.
1588 */
1589 if (min_val > ilog2(BPF_REGISTER_MAX_RANGE))
1590 dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
1591 else if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
1592 dst_reg->min_value <<= min_val;
1593
1594 if (max_val > ilog2(BPF_REGISTER_MAX_RANGE))
1595 dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
1596 else if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
1597 dst_reg->max_value <<= max_val;
1598 break;
1599 case BPF_RSH:
1600 /* RSH by a negative number is undefined, and the BPF_RSH is an
1601 * unsigned shift, so make the appropriate casts.
1602 */
1603 if (min_val < 0 || dst_reg->min_value < 0)
1604 dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
1605 else
1606 dst_reg->min_value =
1607 (u64)(dst_reg->min_value) >> min_val;
1608 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
1609 dst_reg->max_value >>= max_val;
1610 break;
1611 default:
1612 reset_reg_range_values(regs, insn->dst_reg);
1613 break;
1614 }
1615
1616 check_reg_overflow(dst_reg);
1617 }
1618
1619 /* check validity of 32-bit and 64-bit arithmetic operations */
1620 static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
1621 {
1622 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg;
1623 u8 opcode = BPF_OP(insn->code);
1624 int err;
1625
1626 if (opcode == BPF_END || opcode == BPF_NEG) {
1627 if (opcode == BPF_NEG) {
1628 if (BPF_SRC(insn->code) != 0 ||
1629 insn->src_reg != BPF_REG_0 ||
1630 insn->off != 0 || insn->imm != 0) {
1631 verbose("BPF_NEG uses reserved fields\n");
1632 return -EINVAL;
1633 }
1634 } else {
1635 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1636 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1637 verbose("BPF_END uses reserved fields\n");
1638 return -EINVAL;
1639 }
1640 }
1641
1642 /* check src operand */
1643 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1644 if (err)
1645 return err;
1646
1647 if (is_pointer_value(env, insn->dst_reg)) {
1648 verbose("R%d pointer arithmetic prohibited\n",
1649 insn->dst_reg);
1650 return -EACCES;
1651 }
1652
1653 /* check dest operand */
1654 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1655 if (err)
1656 return err;
1657
1658 } else if (opcode == BPF_MOV) {
1659
1660 if (BPF_SRC(insn->code) == BPF_X) {
1661 if (insn->imm != 0 || insn->off != 0) {
1662 verbose("BPF_MOV uses reserved fields\n");
1663 return -EINVAL;
1664 }
1665
1666 /* check src operand */
1667 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1668 if (err)
1669 return err;
1670 } else {
1671 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1672 verbose("BPF_MOV uses reserved fields\n");
1673 return -EINVAL;
1674 }
1675 }
1676
1677 /* check dest operand */
1678 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1679 if (err)
1680 return err;
1681
1682 /* we are setting our register to something new, we need to
1683 * reset its range values.
1684 */
1685 reset_reg_range_values(regs, insn->dst_reg);
1686
1687 if (BPF_SRC(insn->code) == BPF_X) {
1688 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1689 /* case: R1 = R2
1690 * copy register state to dest reg
1691 */
1692 regs[insn->dst_reg] = regs[insn->src_reg];
1693 } else {
1694 if (is_pointer_value(env, insn->src_reg)) {
1695 verbose("R%d partial copy of pointer\n",
1696 insn->src_reg);
1697 return -EACCES;
1698 }
1699 mark_reg_unknown_value(regs, insn->dst_reg);
1700 }
1701 } else {
1702 /* case: R = imm
1703 * remember the value we stored into this reg
1704 */
1705 regs[insn->dst_reg].type = CONST_IMM;
1706 regs[insn->dst_reg].imm = insn->imm;
1707 regs[insn->dst_reg].max_value = insn->imm;
1708 regs[insn->dst_reg].min_value = insn->imm;
1709 }
1710
1711 } else if (opcode > BPF_END) {
1712 verbose("invalid BPF_ALU opcode %x\n", opcode);
1713 return -EINVAL;
1714
1715 } else { /* all other ALU ops: and, sub, xor, add, ... */
1716
1717 if (BPF_SRC(insn->code) == BPF_X) {
1718 if (insn->imm != 0 || insn->off != 0) {
1719 verbose("BPF_ALU uses reserved fields\n");
1720 return -EINVAL;
1721 }
1722 /* check src1 operand */
1723 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1724 if (err)
1725 return err;
1726 } else {
1727 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1728 verbose("BPF_ALU uses reserved fields\n");
1729 return -EINVAL;
1730 }
1731 }
1732
1733 /* check src2 operand */
1734 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1735 if (err)
1736 return err;
1737
1738 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1739 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1740 verbose("div by zero\n");
1741 return -EINVAL;
1742 }
1743
1744 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1745 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1746 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1747
1748 if (insn->imm < 0 || insn->imm >= size) {
1749 verbose("invalid shift %d\n", insn->imm);
1750 return -EINVAL;
1751 }
1752 }
1753
1754 /* check dest operand */
1755 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1756 if (err)
1757 return err;
1758
1759 dst_reg = &regs[insn->dst_reg];
1760
1761 /* first we want to adjust our ranges. */
1762 adjust_reg_min_max_vals(env, insn);
1763
1764 /* pattern match 'bpf_add Rx, imm' instruction */
1765 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1766 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) {
1767 dst_reg->type = PTR_TO_STACK;
1768 dst_reg->imm = insn->imm;
1769 return 0;
1770 } else if (opcode == BPF_ADD &&
1771 BPF_CLASS(insn->code) == BPF_ALU64 &&
1772 (dst_reg->type == PTR_TO_PACKET ||
1773 (BPF_SRC(insn->code) == BPF_X &&
1774 regs[insn->src_reg].type == PTR_TO_PACKET))) {
1775 /* ptr_to_packet += K|X */
1776 return check_packet_ptr_add(env, insn);
1777 } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
1778 dst_reg->type == UNKNOWN_VALUE &&
1779 env->allow_ptr_leaks) {
1780 /* unknown += K|X */
1781 return evaluate_reg_alu(env, insn);
1782 } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
1783 dst_reg->type == CONST_IMM &&
1784 env->allow_ptr_leaks) {
1785 /* reg_imm += K|X */
1786 return evaluate_reg_imm_alu(env, insn);
1787 } else if (is_pointer_value(env, insn->dst_reg)) {
1788 verbose("R%d pointer arithmetic prohibited\n",
1789 insn->dst_reg);
1790 return -EACCES;
1791 } else if (BPF_SRC(insn->code) == BPF_X &&
1792 is_pointer_value(env, insn->src_reg)) {
1793 verbose("R%d pointer arithmetic prohibited\n",
1794 insn->src_reg);
1795 return -EACCES;
1796 }
1797
1798 /* If we did pointer math on a map value then just set it to our
1799 * PTR_TO_MAP_VALUE_ADJ type so we can deal with any stores or
1800 * loads to this register appropriately, otherwise just mark the
1801 * register as unknown.
1802 */
1803 if (env->allow_ptr_leaks &&
1804 (dst_reg->type == PTR_TO_MAP_VALUE ||
1805 dst_reg->type == PTR_TO_MAP_VALUE_ADJ))
1806 dst_reg->type = PTR_TO_MAP_VALUE_ADJ;
1807 else
1808 mark_reg_unknown_value(regs, insn->dst_reg);
1809 }
1810
1811 return 0;
1812 }
1813
1814 static void find_good_pkt_pointers(struct bpf_verifier_state *state,
1815 struct bpf_reg_state *dst_reg)
1816 {
1817 struct bpf_reg_state *regs = state->regs, *reg;
1818 int i;
1819
1820 /* LLVM can generate two kind of checks:
1821 *
1822 * Type 1:
1823 *
1824 * r2 = r3;
1825 * r2 += 8;
1826 * if (r2 > pkt_end) goto <handle exception>
1827 * <access okay>
1828 *
1829 * Where:
1830 * r2 == dst_reg, pkt_end == src_reg
1831 * r2=pkt(id=n,off=8,r=0)
1832 * r3=pkt(id=n,off=0,r=0)
1833 *
1834 * Type 2:
1835 *
1836 * r2 = r3;
1837 * r2 += 8;
1838 * if (pkt_end >= r2) goto <access okay>
1839 * <handle exception>
1840 *
1841 * Where:
1842 * pkt_end == dst_reg, r2 == src_reg
1843 * r2=pkt(id=n,off=8,r=0)
1844 * r3=pkt(id=n,off=0,r=0)
1845 *
1846 * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
1847 * so that range of bytes [r3, r3 + 8) is safe to access.
1848 */
1849
1850 for (i = 0; i < MAX_BPF_REG; i++)
1851 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
1852 regs[i].range = dst_reg->off;
1853
1854 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1855 if (state->stack_slot_type[i] != STACK_SPILL)
1856 continue;
1857 reg = &state->spilled_regs[i / BPF_REG_SIZE];
1858 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
1859 reg->range = dst_reg->off;
1860 }
1861 }
1862
1863 /* Adjusts the register min/max values in the case that the dst_reg is the
1864 * variable register that we are working on, and src_reg is a constant or we're
1865 * simply doing a BPF_K check.
1866 */
1867 static void reg_set_min_max(struct bpf_reg_state *true_reg,
1868 struct bpf_reg_state *false_reg, u64 val,
1869 u8 opcode)
1870 {
1871 switch (opcode) {
1872 case BPF_JEQ:
1873 /* If this is false then we know nothing Jon Snow, but if it is
1874 * true then we know for sure.
1875 */
1876 true_reg->max_value = true_reg->min_value = val;
1877 break;
1878 case BPF_JNE:
1879 /* If this is true we know nothing Jon Snow, but if it is false
1880 * we know the value for sure;
1881 */
1882 false_reg->max_value = false_reg->min_value = val;
1883 break;
1884 case BPF_JGT:
1885 /* Unsigned comparison, the minimum value is 0. */
1886 false_reg->min_value = 0;
1887 case BPF_JSGT:
1888 /* If this is false then we know the maximum val is val,
1889 * otherwise we know the min val is val+1.
1890 */
1891 false_reg->max_value = val;
1892 true_reg->min_value = val + 1;
1893 break;
1894 case BPF_JGE:
1895 /* Unsigned comparison, the minimum value is 0. */
1896 false_reg->min_value = 0;
1897 case BPF_JSGE:
1898 /* If this is false then we know the maximum value is val - 1,
1899 * otherwise we know the mimimum value is val.
1900 */
1901 false_reg->max_value = val - 1;
1902 true_reg->min_value = val;
1903 break;
1904 default:
1905 break;
1906 }
1907
1908 check_reg_overflow(false_reg);
1909 check_reg_overflow(true_reg);
1910 }
1911
1912 /* Same as above, but for the case that dst_reg is a CONST_IMM reg and src_reg
1913 * is the variable reg.
1914 */
1915 static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
1916 struct bpf_reg_state *false_reg, u64 val,
1917 u8 opcode)
1918 {
1919 switch (opcode) {
1920 case BPF_JEQ:
1921 /* If this is false then we know nothing Jon Snow, but if it is
1922 * true then we know for sure.
1923 */
1924 true_reg->max_value = true_reg->min_value = val;
1925 break;
1926 case BPF_JNE:
1927 /* If this is true we know nothing Jon Snow, but if it is false
1928 * we know the value for sure;
1929 */
1930 false_reg->max_value = false_reg->min_value = val;
1931 break;
1932 case BPF_JGT:
1933 /* Unsigned comparison, the minimum value is 0. */
1934 true_reg->min_value = 0;
1935 case BPF_JSGT:
1936 /*
1937 * If this is false, then the val is <= the register, if it is
1938 * true the register <= to the val.
1939 */
1940 false_reg->min_value = val;
1941 true_reg->max_value = val - 1;
1942 break;
1943 case BPF_JGE:
1944 /* Unsigned comparison, the minimum value is 0. */
1945 true_reg->min_value = 0;
1946 case BPF_JSGE:
1947 /* If this is false then constant < register, if it is true then
1948 * the register < constant.
1949 */
1950 false_reg->min_value = val + 1;
1951 true_reg->max_value = val;
1952 break;
1953 default:
1954 break;
1955 }
1956
1957 check_reg_overflow(false_reg);
1958 check_reg_overflow(true_reg);
1959 }
1960
1961 static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
1962 enum bpf_reg_type type)
1963 {
1964 struct bpf_reg_state *reg = &regs[regno];
1965
1966 if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) {
1967 reg->type = type;
1968 if (type == UNKNOWN_VALUE)
1969 mark_reg_unknown_value(regs, regno);
1970 }
1971 }
1972
1973 /* The logic is similar to find_good_pkt_pointers(), both could eventually
1974 * be folded together at some point.
1975 */
1976 static void mark_map_regs(struct bpf_verifier_state *state, u32 regno,
1977 enum bpf_reg_type type)
1978 {
1979 struct bpf_reg_state *regs = state->regs;
1980 int i;
1981
1982 for (i = 0; i < MAX_BPF_REG; i++)
1983 mark_map_reg(regs, i, regs[regno].id, type);
1984
1985 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1986 if (state->stack_slot_type[i] != STACK_SPILL)
1987 continue;
1988 mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE,
1989 regs[regno].id, type);
1990 }
1991 }
1992
1993 static int check_cond_jmp_op(struct bpf_verifier_env *env,
1994 struct bpf_insn *insn, int *insn_idx)
1995 {
1996 struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state;
1997 struct bpf_reg_state *regs = this_branch->regs, *dst_reg;
1998 u8 opcode = BPF_OP(insn->code);
1999 int err;
2000
2001 if (opcode > BPF_EXIT) {
2002 verbose("invalid BPF_JMP opcode %x\n", opcode);
2003 return -EINVAL;
2004 }
2005
2006 if (BPF_SRC(insn->code) == BPF_X) {
2007 if (insn->imm != 0) {
2008 verbose("BPF_JMP uses reserved fields\n");
2009 return -EINVAL;
2010 }
2011
2012 /* check src1 operand */
2013 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2014 if (err)
2015 return err;
2016
2017 if (is_pointer_value(env, insn->src_reg)) {
2018 verbose("R%d pointer comparison prohibited\n",
2019 insn->src_reg);
2020 return -EACCES;
2021 }
2022 } else {
2023 if (insn->src_reg != BPF_REG_0) {
2024 verbose("BPF_JMP uses reserved fields\n");
2025 return -EINVAL;
2026 }
2027 }
2028
2029 /* check src2 operand */
2030 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2031 if (err)
2032 return err;
2033
2034 dst_reg = &regs[insn->dst_reg];
2035
2036 /* detect if R == 0 where R was initialized to zero earlier */
2037 if (BPF_SRC(insn->code) == BPF_K &&
2038 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
2039 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) {
2040 if (opcode == BPF_JEQ) {
2041 /* if (imm == imm) goto pc+off;
2042 * only follow the goto, ignore fall-through
2043 */
2044 *insn_idx += insn->off;
2045 return 0;
2046 } else {
2047 /* if (imm != imm) goto pc+off;
2048 * only follow fall-through branch, since
2049 * that's where the program will go
2050 */
2051 return 0;
2052 }
2053 }
2054
2055 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
2056 if (!other_branch)
2057 return -EFAULT;
2058
2059 /* detect if we are comparing against a constant value so we can adjust
2060 * our min/max values for our dst register.
2061 */
2062 if (BPF_SRC(insn->code) == BPF_X) {
2063 if (regs[insn->src_reg].type == CONST_IMM)
2064 reg_set_min_max(&other_branch->regs[insn->dst_reg],
2065 dst_reg, regs[insn->src_reg].imm,
2066 opcode);
2067 else if (dst_reg->type == CONST_IMM)
2068 reg_set_min_max_inv(&other_branch->regs[insn->src_reg],
2069 &regs[insn->src_reg], dst_reg->imm,
2070 opcode);
2071 } else {
2072 reg_set_min_max(&other_branch->regs[insn->dst_reg],
2073 dst_reg, insn->imm, opcode);
2074 }
2075
2076 /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */
2077 if (BPF_SRC(insn->code) == BPF_K &&
2078 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
2079 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
2080 /* Mark all identical map registers in each branch as either
2081 * safe or unknown depending R == 0 or R != 0 conditional.
2082 */
2083 mark_map_regs(this_branch, insn->dst_reg,
2084 opcode == BPF_JEQ ? PTR_TO_MAP_VALUE : UNKNOWN_VALUE);
2085 mark_map_regs(other_branch, insn->dst_reg,
2086 opcode == BPF_JEQ ? UNKNOWN_VALUE : PTR_TO_MAP_VALUE);
2087 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
2088 dst_reg->type == PTR_TO_PACKET &&
2089 regs[insn->src_reg].type == PTR_TO_PACKET_END) {
2090 find_good_pkt_pointers(this_branch, dst_reg);
2091 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
2092 dst_reg->type == PTR_TO_PACKET_END &&
2093 regs[insn->src_reg].type == PTR_TO_PACKET) {
2094 find_good_pkt_pointers(other_branch, &regs[insn->src_reg]);
2095 } else if (is_pointer_value(env, insn->dst_reg)) {
2096 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
2097 return -EACCES;
2098 }
2099 if (log_level)
2100 print_verifier_state(this_branch);
2101 return 0;
2102 }
2103
2104 /* return the map pointer stored inside BPF_LD_IMM64 instruction */
2105 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
2106 {
2107 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
2108
2109 return (struct bpf_map *) (unsigned long) imm64;
2110 }
2111
2112 /* verify BPF_LD_IMM64 instruction */
2113 static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
2114 {
2115 struct bpf_reg_state *regs = env->cur_state.regs;
2116 int err;
2117
2118 if (BPF_SIZE(insn->code) != BPF_DW) {
2119 verbose("invalid BPF_LD_IMM insn\n");
2120 return -EINVAL;
2121 }
2122 if (insn->off != 0) {
2123 verbose("BPF_LD_IMM64 uses reserved fields\n");
2124 return -EINVAL;
2125 }
2126
2127 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
2128 if (err)
2129 return err;
2130
2131 if (insn->src_reg == 0) {
2132 /* generic move 64-bit immediate into a register,
2133 * only analyzer needs to collect the ld_imm value.
2134 */
2135 u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
2136
2137 if (!env->analyzer_ops)
2138 return 0;
2139
2140 regs[insn->dst_reg].type = CONST_IMM;
2141 regs[insn->dst_reg].imm = imm;
2142 return 0;
2143 }
2144
2145 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
2146 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
2147
2148 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
2149 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
2150 return 0;
2151 }
2152
2153 static bool may_access_skb(enum bpf_prog_type type)
2154 {
2155 switch (type) {
2156 case BPF_PROG_TYPE_SOCKET_FILTER:
2157 case BPF_PROG_TYPE_SCHED_CLS:
2158 case BPF_PROG_TYPE_SCHED_ACT:
2159 return true;
2160 default:
2161 return false;
2162 }
2163 }
2164
2165 /* verify safety of LD_ABS|LD_IND instructions:
2166 * - they can only appear in the programs where ctx == skb
2167 * - since they are wrappers of function calls, they scratch R1-R5 registers,
2168 * preserve R6-R9, and store return value into R0
2169 *
2170 * Implicit input:
2171 * ctx == skb == R6 == CTX
2172 *
2173 * Explicit input:
2174 * SRC == any register
2175 * IMM == 32-bit immediate
2176 *
2177 * Output:
2178 * R0 - 8/16/32-bit skb data converted to cpu endianness
2179 */
2180 static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
2181 {
2182 struct bpf_reg_state *regs = env->cur_state.regs;
2183 u8 mode = BPF_MODE(insn->code);
2184 struct bpf_reg_state *reg;
2185 int i, err;
2186
2187 if (!may_access_skb(env->prog->type)) {
2188 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
2189 return -EINVAL;
2190 }
2191
2192 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
2193 BPF_SIZE(insn->code) == BPF_DW ||
2194 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
2195 verbose("BPF_LD_[ABS|IND] uses reserved fields\n");
2196 return -EINVAL;
2197 }
2198
2199 /* check whether implicit source operand (register R6) is readable */
2200 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
2201 if (err)
2202 return err;
2203
2204 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
2205 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
2206 return -EINVAL;
2207 }
2208
2209 if (mode == BPF_IND) {
2210 /* check explicit source operand */
2211 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2212 if (err)
2213 return err;
2214 }
2215
2216 /* reset caller saved regs to unreadable */
2217 for (i = 0; i < CALLER_SAVED_REGS; i++) {
2218 reg = regs + caller_saved[i];
2219 reg->type = NOT_INIT;
2220 reg->imm = 0;
2221 }
2222
2223 /* mark destination R0 register as readable, since it contains
2224 * the value fetched from the packet
2225 */
2226 regs[BPF_REG_0].type = UNKNOWN_VALUE;
2227 return 0;
2228 }
2229
2230 /* non-recursive DFS pseudo code
2231 * 1 procedure DFS-iterative(G,v):
2232 * 2 label v as discovered
2233 * 3 let S be a stack
2234 * 4 S.push(v)
2235 * 5 while S is not empty
2236 * 6 t <- S.pop()
2237 * 7 if t is what we're looking for:
2238 * 8 return t
2239 * 9 for all edges e in G.adjacentEdges(t) do
2240 * 10 if edge e is already labelled
2241 * 11 continue with the next edge
2242 * 12 w <- G.adjacentVertex(t,e)
2243 * 13 if vertex w is not discovered and not explored
2244 * 14 label e as tree-edge
2245 * 15 label w as discovered
2246 * 16 S.push(w)
2247 * 17 continue at 5
2248 * 18 else if vertex w is discovered
2249 * 19 label e as back-edge
2250 * 20 else
2251 * 21 // vertex w is explored
2252 * 22 label e as forward- or cross-edge
2253 * 23 label t as explored
2254 * 24 S.pop()
2255 *
2256 * convention:
2257 * 0x10 - discovered
2258 * 0x11 - discovered and fall-through edge labelled
2259 * 0x12 - discovered and fall-through and branch edges labelled
2260 * 0x20 - explored
2261 */
2262
2263 enum {
2264 DISCOVERED = 0x10,
2265 EXPLORED = 0x20,
2266 FALLTHROUGH = 1,
2267 BRANCH = 2,
2268 };
2269
2270 #define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L)
2271
2272 static int *insn_stack; /* stack of insns to process */
2273 static int cur_stack; /* current stack index */
2274 static int *insn_state;
2275
2276 /* t, w, e - match pseudo-code above:
2277 * t - index of current instruction
2278 * w - next instruction
2279 * e - edge
2280 */
2281 static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
2282 {
2283 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
2284 return 0;
2285
2286 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
2287 return 0;
2288
2289 if (w < 0 || w >= env->prog->len) {
2290 verbose("jump out of range from insn %d to %d\n", t, w);
2291 return -EINVAL;
2292 }
2293
2294 if (e == BRANCH)
2295 /* mark branch target for state pruning */
2296 env->explored_states[w] = STATE_LIST_MARK;
2297
2298 if (insn_state[w] == 0) {
2299 /* tree-edge */
2300 insn_state[t] = DISCOVERED | e;
2301 insn_state[w] = DISCOVERED;
2302 if (cur_stack >= env->prog->len)
2303 return -E2BIG;
2304 insn_stack[cur_stack++] = w;
2305 return 1;
2306 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
2307 verbose("back-edge from insn %d to %d\n", t, w);
2308 return -EINVAL;
2309 } else if (insn_state[w] == EXPLORED) {
2310 /* forward- or cross-edge */
2311 insn_state[t] = DISCOVERED | e;
2312 } else {
2313 verbose("insn state internal bug\n");
2314 return -EFAULT;
2315 }
2316 return 0;
2317 }
2318
2319 /* non-recursive depth-first-search to detect loops in BPF program
2320 * loop == back-edge in directed graph
2321 */
2322 static int check_cfg(struct bpf_verifier_env *env)
2323 {
2324 struct bpf_insn *insns = env->prog->insnsi;
2325 int insn_cnt = env->prog->len;
2326 int ret = 0;
2327 int i, t;
2328
2329 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
2330 if (!insn_state)
2331 return -ENOMEM;
2332
2333 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
2334 if (!insn_stack) {
2335 kfree(insn_state);
2336 return -ENOMEM;
2337 }
2338
2339 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
2340 insn_stack[0] = 0; /* 0 is the first instruction */
2341 cur_stack = 1;
2342
2343 peek_stack:
2344 if (cur_stack == 0)
2345 goto check_state;
2346 t = insn_stack[cur_stack - 1];
2347
2348 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
2349 u8 opcode = BPF_OP(insns[t].code);
2350
2351 if (opcode == BPF_EXIT) {
2352 goto mark_explored;
2353 } else if (opcode == BPF_CALL) {
2354 ret = push_insn(t, t + 1, FALLTHROUGH, env);
2355 if (ret == 1)
2356 goto peek_stack;
2357 else if (ret < 0)
2358 goto err_free;
2359 if (t + 1 < insn_cnt)
2360 env->explored_states[t + 1] = STATE_LIST_MARK;
2361 } else if (opcode == BPF_JA) {
2362 if (BPF_SRC(insns[t].code) != BPF_K) {
2363 ret = -EINVAL;
2364 goto err_free;
2365 }
2366 /* unconditional jump with single edge */
2367 ret = push_insn(t, t + insns[t].off + 1,
2368 FALLTHROUGH, env);
2369 if (ret == 1)
2370 goto peek_stack;
2371 else if (ret < 0)
2372 goto err_free;
2373 /* tell verifier to check for equivalent states
2374 * after every call and jump
2375 */
2376 if (t + 1 < insn_cnt)
2377 env->explored_states[t + 1] = STATE_LIST_MARK;
2378 } else {
2379 /* conditional jump with two edges */
2380 ret = push_insn(t, t + 1, FALLTHROUGH, env);
2381 if (ret == 1)
2382 goto peek_stack;
2383 else if (ret < 0)
2384 goto err_free;
2385
2386 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
2387 if (ret == 1)
2388 goto peek_stack;
2389 else if (ret < 0)
2390 goto err_free;
2391 }
2392 } else {
2393 /* all other non-branch instructions with single
2394 * fall-through edge
2395 */
2396 ret = push_insn(t, t + 1, FALLTHROUGH, env);
2397 if (ret == 1)
2398 goto peek_stack;
2399 else if (ret < 0)
2400 goto err_free;
2401 }
2402
2403 mark_explored:
2404 insn_state[t] = EXPLORED;
2405 if (cur_stack-- <= 0) {
2406 verbose("pop stack internal bug\n");
2407 ret = -EFAULT;
2408 goto err_free;
2409 }
2410 goto peek_stack;
2411
2412 check_state:
2413 for (i = 0; i < insn_cnt; i++) {
2414 if (insn_state[i] != EXPLORED) {
2415 verbose("unreachable insn %d\n", i);
2416 ret = -EINVAL;
2417 goto err_free;
2418 }
2419 }
2420 ret = 0; /* cfg looks good */
2421
2422 err_free:
2423 kfree(insn_state);
2424 kfree(insn_stack);
2425 return ret;
2426 }
2427
2428 /* the following conditions reduce the number of explored insns
2429 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet
2430 */
2431 static bool compare_ptrs_to_packet(struct bpf_reg_state *old,
2432 struct bpf_reg_state *cur)
2433 {
2434 if (old->id != cur->id)
2435 return false;
2436
2437 /* old ptr_to_packet is more conservative, since it allows smaller
2438 * range. Ex:
2439 * old(off=0,r=10) is equal to cur(off=0,r=20), because
2440 * old(off=0,r=10) means that with range=10 the verifier proceeded
2441 * further and found no issues with the program. Now we're in the same
2442 * spot with cur(off=0,r=20), so we're safe too, since anything further
2443 * will only be looking at most 10 bytes after this pointer.
2444 */
2445 if (old->off == cur->off && old->range < cur->range)
2446 return true;
2447
2448 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0)
2449 * since both cannot be used for packet access and safe(old)
2450 * pointer has smaller off that could be used for further
2451 * 'if (ptr > data_end)' check
2452 * Ex:
2453 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean
2454 * that we cannot access the packet.
2455 * The safe range is:
2456 * [ptr, ptr + range - off)
2457 * so whenever off >=range, it means no safe bytes from this pointer.
2458 * When comparing old->off <= cur->off, it means that older code
2459 * went with smaller offset and that offset was later
2460 * used to figure out the safe range after 'if (ptr > data_end)' check
2461 * Say, 'old' state was explored like:
2462 * ... R3(off=0, r=0)
2463 * R4 = R3 + 20
2464 * ... now R4(off=20,r=0) <-- here
2465 * if (R4 > data_end)
2466 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access.
2467 * ... the code further went all the way to bpf_exit.
2468 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0).
2469 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier
2470 * goes further, such cur_R4 will give larger safe packet range after
2471 * 'if (R4 > data_end)' and all further insn were already good with r=20,
2472 * so they will be good with r=30 and we can prune the search.
2473 */
2474 if (old->off <= cur->off &&
2475 old->off >= old->range && cur->off >= cur->range)
2476 return true;
2477
2478 return false;
2479 }
2480
2481 /* compare two verifier states
2482 *
2483 * all states stored in state_list are known to be valid, since
2484 * verifier reached 'bpf_exit' instruction through them
2485 *
2486 * this function is called when verifier exploring different branches of
2487 * execution popped from the state stack. If it sees an old state that has
2488 * more strict register state and more strict stack state then this execution
2489 * branch doesn't need to be explored further, since verifier already
2490 * concluded that more strict state leads to valid finish.
2491 *
2492 * Therefore two states are equivalent if register state is more conservative
2493 * and explored stack state is more conservative than the current one.
2494 * Example:
2495 * explored current
2496 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
2497 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
2498 *
2499 * In other words if current stack state (one being explored) has more
2500 * valid slots than old one that already passed validation, it means
2501 * the verifier can stop exploring and conclude that current state is valid too
2502 *
2503 * Similarly with registers. If explored state has register type as invalid
2504 * whereas register type in current state is meaningful, it means that
2505 * the current state will reach 'bpf_exit' instruction safely
2506 */
2507 static bool states_equal(struct bpf_verifier_env *env,
2508 struct bpf_verifier_state *old,
2509 struct bpf_verifier_state *cur)
2510 {
2511 struct bpf_reg_state *rold, *rcur;
2512 int i;
2513
2514 for (i = 0; i < MAX_BPF_REG; i++) {
2515 rold = &old->regs[i];
2516 rcur = &cur->regs[i];
2517
2518 if (memcmp(rold, rcur, sizeof(*rold)) == 0)
2519 continue;
2520
2521 /* If the ranges were not the same, but everything else was and
2522 * we didn't do a variable access into a map then we are a-ok.
2523 */
2524 if (!env->varlen_map_value_access &&
2525 rold->type == rcur->type && rold->imm == rcur->imm)
2526 continue;
2527
2528 if (rold->type == NOT_INIT ||
2529 (rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT))
2530 continue;
2531
2532 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET &&
2533 compare_ptrs_to_packet(rold, rcur))
2534 continue;
2535
2536 return false;
2537 }
2538
2539 for (i = 0; i < MAX_BPF_STACK; i++) {
2540 if (old->stack_slot_type[i] == STACK_INVALID)
2541 continue;
2542 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
2543 /* Ex: old explored (safe) state has STACK_SPILL in
2544 * this stack slot, but current has has STACK_MISC ->
2545 * this verifier states are not equivalent,
2546 * return false to continue verification of this path
2547 */
2548 return false;
2549 if (i % BPF_REG_SIZE)
2550 continue;
2551 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
2552 &cur->spilled_regs[i / BPF_REG_SIZE],
2553 sizeof(old->spilled_regs[0])))
2554 /* when explored and current stack slot types are
2555 * the same, check that stored pointers types
2556 * are the same as well.
2557 * Ex: explored safe path could have stored
2558 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -8}
2559 * but current path has stored:
2560 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -16}
2561 * such verifier states are not equivalent.
2562 * return false to continue verification of this path
2563 */
2564 return false;
2565 else
2566 continue;
2567 }
2568 return true;
2569 }
2570
2571 static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
2572 {
2573 struct bpf_verifier_state_list *new_sl;
2574 struct bpf_verifier_state_list *sl;
2575
2576 sl = env->explored_states[insn_idx];
2577 if (!sl)
2578 /* this 'insn_idx' instruction wasn't marked, so we will not
2579 * be doing state search here
2580 */
2581 return 0;
2582
2583 while (sl != STATE_LIST_MARK) {
2584 if (states_equal(env, &sl->state, &env->cur_state))
2585 /* reached equivalent register/stack state,
2586 * prune the search
2587 */
2588 return 1;
2589 sl = sl->next;
2590 }
2591
2592 /* there were no equivalent states, remember current one.
2593 * technically the current state is not proven to be safe yet,
2594 * but it will either reach bpf_exit (which means it's safe) or
2595 * it will be rejected. Since there are no loops, we won't be
2596 * seeing this 'insn_idx' instruction again on the way to bpf_exit
2597 */
2598 new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER);
2599 if (!new_sl)
2600 return -ENOMEM;
2601
2602 /* add new state to the head of linked list */
2603 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
2604 new_sl->next = env->explored_states[insn_idx];
2605 env->explored_states[insn_idx] = new_sl;
2606 return 0;
2607 }
2608
2609 static int ext_analyzer_insn_hook(struct bpf_verifier_env *env,
2610 int insn_idx, int prev_insn_idx)
2611 {
2612 if (!env->analyzer_ops || !env->analyzer_ops->insn_hook)
2613 return 0;
2614
2615 return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx);
2616 }
2617
2618 static int do_check(struct bpf_verifier_env *env)
2619 {
2620 struct bpf_verifier_state *state = &env->cur_state;
2621 struct bpf_insn *insns = env->prog->insnsi;
2622 struct bpf_reg_state *regs = state->regs;
2623 int insn_cnt = env->prog->len;
2624 int insn_idx, prev_insn_idx = 0;
2625 int insn_processed = 0;
2626 bool do_print_state = false;
2627
2628 init_reg_state(regs);
2629 insn_idx = 0;
2630 env->varlen_map_value_access = false;
2631 for (;;) {
2632 struct bpf_insn *insn;
2633 u8 class;
2634 int err;
2635
2636 if (insn_idx >= insn_cnt) {
2637 verbose("invalid insn idx %d insn_cnt %d\n",
2638 insn_idx, insn_cnt);
2639 return -EFAULT;
2640 }
2641
2642 insn = &insns[insn_idx];
2643 class = BPF_CLASS(insn->code);
2644
2645 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
2646 verbose("BPF program is too large. Proccessed %d insn\n",
2647 insn_processed);
2648 return -E2BIG;
2649 }
2650
2651 err = is_state_visited(env, insn_idx);
2652 if (err < 0)
2653 return err;
2654 if (err == 1) {
2655 /* found equivalent state, can prune the search */
2656 if (log_level) {
2657 if (do_print_state)
2658 verbose("\nfrom %d to %d: safe\n",
2659 prev_insn_idx, insn_idx);
2660 else
2661 verbose("%d: safe\n", insn_idx);
2662 }
2663 goto process_bpf_exit;
2664 }
2665
2666 if (log_level && do_print_state) {
2667 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
2668 print_verifier_state(&env->cur_state);
2669 do_print_state = false;
2670 }
2671
2672 if (log_level) {
2673 verbose("%d: ", insn_idx);
2674 print_bpf_insn(insn);
2675 }
2676
2677 err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx);
2678 if (err)
2679 return err;
2680
2681 if (class == BPF_ALU || class == BPF_ALU64) {
2682 err = check_alu_op(env, insn);
2683 if (err)
2684 return err;
2685
2686 } else if (class == BPF_LDX) {
2687 enum bpf_reg_type *prev_src_type, src_reg_type;
2688
2689 /* check for reserved fields is already done */
2690
2691 /* check src operand */
2692 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2693 if (err)
2694 return err;
2695
2696 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
2697 if (err)
2698 return err;
2699
2700 src_reg_type = regs[insn->src_reg].type;
2701
2702 /* check that memory (src_reg + off) is readable,
2703 * the state of dst_reg will be updated by this func
2704 */
2705 err = check_mem_access(env, insn->src_reg, insn->off,
2706 BPF_SIZE(insn->code), BPF_READ,
2707 insn->dst_reg);
2708 if (err)
2709 return err;
2710
2711 reset_reg_range_values(regs, insn->dst_reg);
2712 if (BPF_SIZE(insn->code) != BPF_W &&
2713 BPF_SIZE(insn->code) != BPF_DW) {
2714 insn_idx++;
2715 continue;
2716 }
2717
2718 prev_src_type = &env->insn_aux_data[insn_idx].ptr_type;
2719
2720 if (*prev_src_type == NOT_INIT) {
2721 /* saw a valid insn
2722 * dst_reg = *(u32 *)(src_reg + off)
2723 * save type to validate intersecting paths
2724 */
2725 *prev_src_type = src_reg_type;
2726
2727 } else if (src_reg_type != *prev_src_type &&
2728 (src_reg_type == PTR_TO_CTX ||
2729 *prev_src_type == PTR_TO_CTX)) {
2730 /* ABuser program is trying to use the same insn
2731 * dst_reg = *(u32*) (src_reg + off)
2732 * with different pointer types:
2733 * src_reg == ctx in one branch and
2734 * src_reg == stack|map in some other branch.
2735 * Reject it.
2736 */
2737 verbose("same insn cannot be used with different pointers\n");
2738 return -EINVAL;
2739 }
2740
2741 } else if (class == BPF_STX) {
2742 enum bpf_reg_type *prev_dst_type, dst_reg_type;
2743
2744 if (BPF_MODE(insn->code) == BPF_XADD) {
2745 err = check_xadd(env, insn);
2746 if (err)
2747 return err;
2748 insn_idx++;
2749 continue;
2750 }
2751
2752 /* check src1 operand */
2753 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2754 if (err)
2755 return err;
2756 /* check src2 operand */
2757 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2758 if (err)
2759 return err;
2760
2761 dst_reg_type = regs[insn->dst_reg].type;
2762
2763 /* check that memory (dst_reg + off) is writeable */
2764 err = check_mem_access(env, insn->dst_reg, insn->off,
2765 BPF_SIZE(insn->code), BPF_WRITE,
2766 insn->src_reg);
2767 if (err)
2768 return err;
2769
2770 prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type;
2771
2772 if (*prev_dst_type == NOT_INIT) {
2773 *prev_dst_type = dst_reg_type;
2774 } else if (dst_reg_type != *prev_dst_type &&
2775 (dst_reg_type == PTR_TO_CTX ||
2776 *prev_dst_type == PTR_TO_CTX)) {
2777 verbose("same insn cannot be used with different pointers\n");
2778 return -EINVAL;
2779 }
2780
2781 } else if (class == BPF_ST) {
2782 if (BPF_MODE(insn->code) != BPF_MEM ||
2783 insn->src_reg != BPF_REG_0) {
2784 verbose("BPF_ST uses reserved fields\n");
2785 return -EINVAL;
2786 }
2787 /* check src operand */
2788 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2789 if (err)
2790 return err;
2791
2792 /* check that memory (dst_reg + off) is writeable */
2793 err = check_mem_access(env, insn->dst_reg, insn->off,
2794 BPF_SIZE(insn->code), BPF_WRITE,
2795 -1);
2796 if (err)
2797 return err;
2798
2799 } else if (class == BPF_JMP) {
2800 u8 opcode = BPF_OP(insn->code);
2801
2802 if (opcode == BPF_CALL) {
2803 if (BPF_SRC(insn->code) != BPF_K ||
2804 insn->off != 0 ||
2805 insn->src_reg != BPF_REG_0 ||
2806 insn->dst_reg != BPF_REG_0) {
2807 verbose("BPF_CALL uses reserved fields\n");
2808 return -EINVAL;
2809 }
2810
2811 err = check_call(env, insn->imm);
2812 if (err)
2813 return err;
2814
2815 } else if (opcode == BPF_JA) {
2816 if (BPF_SRC(insn->code) != BPF_K ||
2817 insn->imm != 0 ||
2818 insn->src_reg != BPF_REG_0 ||
2819 insn->dst_reg != BPF_REG_0) {
2820 verbose("BPF_JA uses reserved fields\n");
2821 return -EINVAL;
2822 }
2823
2824 insn_idx += insn->off + 1;
2825 continue;
2826
2827 } else if (opcode == BPF_EXIT) {
2828 if (BPF_SRC(insn->code) != BPF_K ||
2829 insn->imm != 0 ||
2830 insn->src_reg != BPF_REG_0 ||
2831 insn->dst_reg != BPF_REG_0) {
2832 verbose("BPF_EXIT uses reserved fields\n");
2833 return -EINVAL;
2834 }
2835
2836 /* eBPF calling convetion is such that R0 is used
2837 * to return the value from eBPF program.
2838 * Make sure that it's readable at this time
2839 * of bpf_exit, which means that program wrote
2840 * something into it earlier
2841 */
2842 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
2843 if (err)
2844 return err;
2845
2846 if (is_pointer_value(env, BPF_REG_0)) {
2847 verbose("R0 leaks addr as return value\n");
2848 return -EACCES;
2849 }
2850
2851 process_bpf_exit:
2852 insn_idx = pop_stack(env, &prev_insn_idx);
2853 if (insn_idx < 0) {
2854 break;
2855 } else {
2856 do_print_state = true;
2857 continue;
2858 }
2859 } else {
2860 err = check_cond_jmp_op(env, insn, &insn_idx);
2861 if (err)
2862 return err;
2863 }
2864 } else if (class == BPF_LD) {
2865 u8 mode = BPF_MODE(insn->code);
2866
2867 if (mode == BPF_ABS || mode == BPF_IND) {
2868 err = check_ld_abs(env, insn);
2869 if (err)
2870 return err;
2871
2872 } else if (mode == BPF_IMM) {
2873 err = check_ld_imm(env, insn);
2874 if (err)
2875 return err;
2876
2877 insn_idx++;
2878 } else {
2879 verbose("invalid BPF_LD mode\n");
2880 return -EINVAL;
2881 }
2882 reset_reg_range_values(regs, insn->dst_reg);
2883 } else {
2884 verbose("unknown insn class %d\n", class);
2885 return -EINVAL;
2886 }
2887
2888 insn_idx++;
2889 }
2890
2891 verbose("processed %d insns\n", insn_processed);
2892 return 0;
2893 }
2894
2895 static int check_map_prog_compatibility(struct bpf_map *map,
2896 struct bpf_prog *prog)
2897
2898 {
2899 if (prog->type == BPF_PROG_TYPE_PERF_EVENT &&
2900 (map->map_type == BPF_MAP_TYPE_HASH ||
2901 map->map_type == BPF_MAP_TYPE_PERCPU_HASH) &&
2902 (map->map_flags & BPF_F_NO_PREALLOC)) {
2903 verbose("perf_event programs can only use preallocated hash map\n");
2904 return -EINVAL;
2905 }
2906 return 0;
2907 }
2908
2909 /* look for pseudo eBPF instructions that access map FDs and
2910 * replace them with actual map pointers
2911 */
2912 static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env)
2913 {
2914 struct bpf_insn *insn = env->prog->insnsi;
2915 int insn_cnt = env->prog->len;
2916 int i, j, err;
2917
2918 for (i = 0; i < insn_cnt; i++, insn++) {
2919 if (BPF_CLASS(insn->code) == BPF_LDX &&
2920 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
2921 verbose("BPF_LDX uses reserved fields\n");
2922 return -EINVAL;
2923 }
2924
2925 if (BPF_CLASS(insn->code) == BPF_STX &&
2926 ((BPF_MODE(insn->code) != BPF_MEM &&
2927 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2928 verbose("BPF_STX uses reserved fields\n");
2929 return -EINVAL;
2930 }
2931
2932 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2933 struct bpf_map *map;
2934 struct fd f;
2935
2936 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2937 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2938 insn[1].off != 0) {
2939 verbose("invalid bpf_ld_imm64 insn\n");
2940 return -EINVAL;
2941 }
2942
2943 if (insn->src_reg == 0)
2944 /* valid generic load 64-bit imm */
2945 goto next_insn;
2946
2947 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2948 verbose("unrecognized bpf_ld_imm64 insn\n");
2949 return -EINVAL;
2950 }
2951
2952 f = fdget(insn->imm);
2953 map = __bpf_map_get(f);
2954 if (IS_ERR(map)) {
2955 verbose("fd %d is not pointing to valid bpf_map\n",
2956 insn->imm);
2957 return PTR_ERR(map);
2958 }
2959
2960 err = check_map_prog_compatibility(map, env->prog);
2961 if (err) {
2962 fdput(f);
2963 return err;
2964 }
2965
2966 /* store map pointer inside BPF_LD_IMM64 instruction */
2967 insn[0].imm = (u32) (unsigned long) map;
2968 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2969
2970 /* check whether we recorded this map already */
2971 for (j = 0; j < env->used_map_cnt; j++)
2972 if (env->used_maps[j] == map) {
2973 fdput(f);
2974 goto next_insn;
2975 }
2976
2977 if (env->used_map_cnt >= MAX_USED_MAPS) {
2978 fdput(f);
2979 return -E2BIG;
2980 }
2981
2982 /* hold the map. If the program is rejected by verifier,
2983 * the map will be released by release_maps() or it
2984 * will be used by the valid program until it's unloaded
2985 * and all maps are released in free_bpf_prog_info()
2986 */
2987 map = bpf_map_inc(map, false);
2988 if (IS_ERR(map)) {
2989 fdput(f);
2990 return PTR_ERR(map);
2991 }
2992 env->used_maps[env->used_map_cnt++] = map;
2993
2994 fdput(f);
2995 next_insn:
2996 insn++;
2997 i++;
2998 }
2999 }
3000
3001 /* now all pseudo BPF_LD_IMM64 instructions load valid
3002 * 'struct bpf_map *' into a register instead of user map_fd.
3003 * These pointers will be used later by verifier to validate map access.
3004 */
3005 return 0;
3006 }
3007
3008 /* drop refcnt of maps used by the rejected program */
3009 static void release_maps(struct bpf_verifier_env *env)
3010 {
3011 int i;
3012
3013 for (i = 0; i < env->used_map_cnt; i++)
3014 bpf_map_put(env->used_maps[i]);
3015 }
3016
3017 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
3018 static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
3019 {
3020 struct bpf_insn *insn = env->prog->insnsi;
3021 int insn_cnt = env->prog->len;
3022 int i;
3023
3024 for (i = 0; i < insn_cnt; i++, insn++)
3025 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
3026 insn->src_reg = 0;
3027 }
3028
3029 /* convert load instructions that access fields of 'struct __sk_buff'
3030 * into sequence of instructions that access fields of 'struct sk_buff'
3031 */
3032 static int convert_ctx_accesses(struct bpf_verifier_env *env)
3033 {
3034 const struct bpf_verifier_ops *ops = env->prog->aux->ops;
3035 const int insn_cnt = env->prog->len;
3036 struct bpf_insn insn_buf[16], *insn;
3037 struct bpf_prog *new_prog;
3038 enum bpf_access_type type;
3039 int i, cnt, delta = 0;
3040
3041 if (ops->gen_prologue) {
3042 cnt = ops->gen_prologue(insn_buf, env->seen_direct_write,
3043 env->prog);
3044 if (cnt >= ARRAY_SIZE(insn_buf)) {
3045 verbose("bpf verifier is misconfigured\n");
3046 return -EINVAL;
3047 } else if (cnt) {
3048 new_prog = bpf_patch_insn_single(env->prog, 0,
3049 insn_buf, cnt);
3050 if (!new_prog)
3051 return -ENOMEM;
3052 env->prog = new_prog;
3053 delta += cnt - 1;
3054 }
3055 }
3056
3057 if (!ops->convert_ctx_access)
3058 return 0;
3059
3060 insn = env->prog->insnsi + delta;
3061
3062 for (i = 0; i < insn_cnt; i++, insn++) {
3063 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
3064 insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
3065 type = BPF_READ;
3066 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
3067 insn->code == (BPF_STX | BPF_MEM | BPF_DW))
3068 type = BPF_WRITE;
3069 else
3070 continue;
3071
3072 if (env->insn_aux_data[i].ptr_type != PTR_TO_CTX)
3073 continue;
3074
3075 cnt = ops->convert_ctx_access(type, insn->dst_reg, insn->src_reg,
3076 insn->off, insn_buf, env->prog);
3077 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
3078 verbose("bpf verifier is misconfigured\n");
3079 return -EINVAL;
3080 }
3081
3082 new_prog = bpf_patch_insn_single(env->prog, i + delta, insn_buf,
3083 cnt);
3084 if (!new_prog)
3085 return -ENOMEM;
3086
3087 delta += cnt - 1;
3088
3089 /* keep walking new program and skip insns we just inserted */
3090 env->prog = new_prog;
3091 insn = new_prog->insnsi + i + delta;
3092 }
3093
3094 return 0;
3095 }
3096
3097 static void free_states(struct bpf_verifier_env *env)
3098 {
3099 struct bpf_verifier_state_list *sl, *sln;
3100 int i;
3101
3102 if (!env->explored_states)
3103 return;
3104
3105 for (i = 0; i < env->prog->len; i++) {
3106 sl = env->explored_states[i];
3107
3108 if (sl)
3109 while (sl != STATE_LIST_MARK) {
3110 sln = sl->next;
3111 kfree(sl);
3112 sl = sln;
3113 }
3114 }
3115
3116 kfree(env->explored_states);
3117 }
3118
3119 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
3120 {
3121 char __user *log_ubuf = NULL;
3122 struct bpf_verifier_env *env;
3123 int ret = -EINVAL;
3124
3125 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
3126 return -E2BIG;
3127
3128 /* 'struct bpf_verifier_env' can be global, but since it's not small,
3129 * allocate/free it every time bpf_check() is called
3130 */
3131 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
3132 if (!env)
3133 return -ENOMEM;
3134
3135 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) *
3136 (*prog)->len);
3137 ret = -ENOMEM;
3138 if (!env->insn_aux_data)
3139 goto err_free_env;
3140 env->prog = *prog;
3141
3142 /* grab the mutex to protect few globals used by verifier */
3143 mutex_lock(&bpf_verifier_lock);
3144
3145 if (attr->log_level || attr->log_buf || attr->log_size) {
3146 /* user requested verbose verifier output
3147 * and supplied buffer to store the verification trace
3148 */
3149 log_level = attr->log_level;
3150 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
3151 log_size = attr->log_size;
3152 log_len = 0;
3153
3154 ret = -EINVAL;
3155 /* log_* values have to be sane */
3156 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
3157 log_level == 0 || log_ubuf == NULL)
3158 goto err_unlock;
3159
3160 ret = -ENOMEM;
3161 log_buf = vmalloc(log_size);
3162 if (!log_buf)
3163 goto err_unlock;
3164 } else {
3165 log_level = 0;
3166 }
3167
3168 ret = replace_map_fd_with_map_ptr(env);
3169 if (ret < 0)
3170 goto skip_full_check;
3171
3172 env->explored_states = kcalloc(env->prog->len,
3173 sizeof(struct bpf_verifier_state_list *),
3174 GFP_USER);
3175 ret = -ENOMEM;
3176 if (!env->explored_states)
3177 goto skip_full_check;
3178
3179 ret = check_cfg(env);
3180 if (ret < 0)
3181 goto skip_full_check;
3182
3183 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
3184
3185 ret = do_check(env);
3186
3187 skip_full_check:
3188 while (pop_stack(env, NULL) >= 0);
3189 free_states(env);
3190
3191 if (ret == 0)
3192 /* program is valid, convert *(u32*)(ctx + off) accesses */
3193 ret = convert_ctx_accesses(env);
3194
3195 if (log_level && log_len >= log_size - 1) {
3196 BUG_ON(log_len >= log_size);
3197 /* verifier log exceeded user supplied buffer */
3198 ret = -ENOSPC;
3199 /* fall through to return what was recorded */
3200 }
3201
3202 /* copy verifier log back to user space including trailing zero */
3203 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
3204 ret = -EFAULT;
3205 goto free_log_buf;
3206 }
3207
3208 if (ret == 0 && env->used_map_cnt) {
3209 /* if program passed verifier, update used_maps in bpf_prog_info */
3210 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
3211 sizeof(env->used_maps[0]),
3212 GFP_KERNEL);
3213
3214 if (!env->prog->aux->used_maps) {
3215 ret = -ENOMEM;
3216 goto free_log_buf;
3217 }
3218
3219 memcpy(env->prog->aux->used_maps, env->used_maps,
3220 sizeof(env->used_maps[0]) * env->used_map_cnt);
3221 env->prog->aux->used_map_cnt = env->used_map_cnt;
3222
3223 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
3224 * bpf_ld_imm64 instructions
3225 */
3226 convert_pseudo_ld_imm64(env);
3227 }
3228
3229 free_log_buf:
3230 if (log_level)
3231 vfree(log_buf);
3232 if (!env->prog->aux->used_maps)
3233 /* if we didn't copy map pointers into bpf_prog_info, release
3234 * them now. Otherwise free_bpf_prog_info() will release them.
3235 */
3236 release_maps(env);
3237 *prog = env->prog;
3238 err_unlock:
3239 mutex_unlock(&bpf_verifier_lock);
3240 vfree(env->insn_aux_data);
3241 err_free_env:
3242 kfree(env);
3243 return ret;
3244 }
3245
3246 int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
3247 void *priv)
3248 {
3249 struct bpf_verifier_env *env;
3250 int ret;
3251
3252 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
3253 if (!env)
3254 return -ENOMEM;
3255
3256 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) *
3257 prog->len);
3258 ret = -ENOMEM;
3259 if (!env->insn_aux_data)
3260 goto err_free_env;
3261 env->prog = prog;
3262 env->analyzer_ops = ops;
3263 env->analyzer_priv = priv;
3264
3265 /* grab the mutex to protect few globals used by verifier */
3266 mutex_lock(&bpf_verifier_lock);
3267
3268 log_level = 0;
3269
3270 env->explored_states = kcalloc(env->prog->len,
3271 sizeof(struct bpf_verifier_state_list *),
3272 GFP_KERNEL);
3273 ret = -ENOMEM;
3274 if (!env->explored_states)
3275 goto skip_full_check;
3276
3277 ret = check_cfg(env);
3278 if (ret < 0)
3279 goto skip_full_check;
3280
3281 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
3282
3283 ret = do_check(env);
3284
3285 skip_full_check:
3286 while (pop_stack(env, NULL) >= 0);
3287 free_states(env);
3288
3289 mutex_unlock(&bpf_verifier_lock);
3290 vfree(env->insn_aux_data);
3291 err_free_env:
3292 kfree(env);
3293 return ret;
3294 }
3295 EXPORT_SYMBOL_GPL(bpf_analyzer);
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