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Merge tag 'usb-4.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
[deliverable/linux.git] / kernel / bpf / verifier.c
1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * This program is distributed in the hope that it will be useful, but
8 * WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
10 * General Public License for more details.
11 */
12 #include <linux/kernel.h>
13 #include <linux/types.h>
14 #include <linux/slab.h>
15 #include <linux/bpf.h>
16 #include <linux/filter.h>
17 #include <net/netlink.h>
18 #include <linux/file.h>
19 #include <linux/vmalloc.h>
20
21 /* bpf_check() is a static code analyzer that walks eBPF program
22 * instruction by instruction and updates register/stack state.
23 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
24 *
25 * The first pass is depth-first-search to check that the program is a DAG.
26 * It rejects the following programs:
27 * - larger than BPF_MAXINSNS insns
28 * - if loop is present (detected via back-edge)
29 * - unreachable insns exist (shouldn't be a forest. program = one function)
30 * - out of bounds or malformed jumps
31 * The second pass is all possible path descent from the 1st insn.
32 * Since it's analyzing all pathes through the program, the length of the
33 * analysis is limited to 32k insn, which may be hit even if total number of
34 * insn is less then 4K, but there are too many branches that change stack/regs.
35 * Number of 'branches to be analyzed' is limited to 1k
36 *
37 * On entry to each instruction, each register has a type, and the instruction
38 * changes the types of the registers depending on instruction semantics.
39 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
40 * copied to R1.
41 *
42 * All registers are 64-bit.
43 * R0 - return register
44 * R1-R5 argument passing registers
45 * R6-R9 callee saved registers
46 * R10 - frame pointer read-only
47 *
48 * At the start of BPF program the register R1 contains a pointer to bpf_context
49 * and has type PTR_TO_CTX.
50 *
51 * Verifier tracks arithmetic operations on pointers in case:
52 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
53 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
54 * 1st insn copies R10 (which has FRAME_PTR) type into R1
55 * and 2nd arithmetic instruction is pattern matched to recognize
56 * that it wants to construct a pointer to some element within stack.
57 * So after 2nd insn, the register R1 has type PTR_TO_STACK
58 * (and -20 constant is saved for further stack bounds checking).
59 * Meaning that this reg is a pointer to stack plus known immediate constant.
60 *
61 * Most of the time the registers have UNKNOWN_VALUE type, which
62 * means the register has some value, but it's not a valid pointer.
63 * (like pointer plus pointer becomes UNKNOWN_VALUE type)
64 *
65 * When verifier sees load or store instructions the type of base register
66 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
67 * types recognized by check_mem_access() function.
68 *
69 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
70 * and the range of [ptr, ptr + map's value_size) is accessible.
71 *
72 * registers used to pass values to function calls are checked against
73 * function argument constraints.
74 *
75 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
76 * It means that the register type passed to this function must be
77 * PTR_TO_STACK and it will be used inside the function as
78 * 'pointer to map element key'
79 *
80 * For example the argument constraints for bpf_map_lookup_elem():
81 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
82 * .arg1_type = ARG_CONST_MAP_PTR,
83 * .arg2_type = ARG_PTR_TO_MAP_KEY,
84 *
85 * ret_type says that this function returns 'pointer to map elem value or null'
86 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
87 * 2nd argument should be a pointer to stack, which will be used inside
88 * the helper function as a pointer to map element key.
89 *
90 * On the kernel side the helper function looks like:
91 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
92 * {
93 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
94 * void *key = (void *) (unsigned long) r2;
95 * void *value;
96 *
97 * here kernel can access 'key' and 'map' pointers safely, knowing that
98 * [key, key + map->key_size) bytes are valid and were initialized on
99 * the stack of eBPF program.
100 * }
101 *
102 * Corresponding eBPF program may look like:
103 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
104 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
105 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
106 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
107 * here verifier looks at prototype of map_lookup_elem() and sees:
108 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
109 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
110 *
111 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
112 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
113 * and were initialized prior to this call.
114 * If it's ok, then verifier allows this BPF_CALL insn and looks at
115 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
116 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
117 * returns ether pointer to map value or NULL.
118 *
119 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
120 * insn, the register holding that pointer in the true branch changes state to
121 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
122 * branch. See check_cond_jmp_op().
123 *
124 * After the call R0 is set to return type of the function and registers R1-R5
125 * are set to NOT_INIT to indicate that they are no longer readable.
126 */
127
128 /* types of values stored in eBPF registers */
129 enum bpf_reg_type {
130 NOT_INIT = 0, /* nothing was written into register */
131 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */
132 PTR_TO_CTX, /* reg points to bpf_context */
133 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */
134 PTR_TO_MAP_VALUE, /* reg points to map element value */
135 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
136 FRAME_PTR, /* reg == frame_pointer */
137 PTR_TO_STACK, /* reg == frame_pointer + imm */
138 CONST_IMM, /* constant integer value */
139 };
140
141 struct reg_state {
142 enum bpf_reg_type type;
143 union {
144 /* valid when type == CONST_IMM | PTR_TO_STACK */
145 int imm;
146
147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
148 * PTR_TO_MAP_VALUE_OR_NULL
149 */
150 struct bpf_map *map_ptr;
151 };
152 };
153
154 enum bpf_stack_slot_type {
155 STACK_INVALID, /* nothing was stored in this stack slot */
156 STACK_SPILL, /* register spilled into stack */
157 STACK_MISC /* BPF program wrote some data into this slot */
158 };
159
160 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
161
162 /* state of the program:
163 * type of all registers and stack info
164 */
165 struct verifier_state {
166 struct reg_state regs[MAX_BPF_REG];
167 u8 stack_slot_type[MAX_BPF_STACK];
168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
169 };
170
171 /* linked list of verifier states used to prune search */
172 struct verifier_state_list {
173 struct verifier_state state;
174 struct verifier_state_list *next;
175 };
176
177 /* verifier_state + insn_idx are pushed to stack when branch is encountered */
178 struct verifier_stack_elem {
179 /* verifer state is 'st'
180 * before processing instruction 'insn_idx'
181 * and after processing instruction 'prev_insn_idx'
182 */
183 struct verifier_state st;
184 int insn_idx;
185 int prev_insn_idx;
186 struct verifier_stack_elem *next;
187 };
188
189 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
190
191 /* single container for all structs
192 * one verifier_env per bpf_check() call
193 */
194 struct verifier_env {
195 struct bpf_prog *prog; /* eBPF program being verified */
196 struct verifier_stack_elem *head; /* stack of verifier states to be processed */
197 int stack_size; /* number of states to be processed */
198 struct verifier_state cur_state; /* current verifier state */
199 struct verifier_state_list **explored_states; /* search pruning optimization */
200 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
201 u32 used_map_cnt; /* number of used maps */
202 bool allow_ptr_leaks;
203 };
204
205 /* verbose verifier prints what it's seeing
206 * bpf_check() is called under lock, so no race to access these global vars
207 */
208 static u32 log_level, log_size, log_len;
209 static char *log_buf;
210
211 static DEFINE_MUTEX(bpf_verifier_lock);
212
213 /* log_level controls verbosity level of eBPF verifier.
214 * verbose() is used to dump the verification trace to the log, so the user
215 * can figure out what's wrong with the program
216 */
217 static __printf(1, 2) void verbose(const char *fmt, ...)
218 {
219 va_list args;
220
221 if (log_level == 0 || log_len >= log_size - 1)
222 return;
223
224 va_start(args, fmt);
225 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
226 va_end(args);
227 }
228
229 /* string representation of 'enum bpf_reg_type' */
230 static const char * const reg_type_str[] = {
231 [NOT_INIT] = "?",
232 [UNKNOWN_VALUE] = "inv",
233 [PTR_TO_CTX] = "ctx",
234 [CONST_PTR_TO_MAP] = "map_ptr",
235 [PTR_TO_MAP_VALUE] = "map_value",
236 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
237 [FRAME_PTR] = "fp",
238 [PTR_TO_STACK] = "fp",
239 [CONST_IMM] = "imm",
240 };
241
242 static const struct {
243 int map_type;
244 int func_id;
245 } func_limit[] = {
246 {BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
247 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
248 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
249 {BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid},
250 };
251
252 static void print_verifier_state(struct verifier_env *env)
253 {
254 enum bpf_reg_type t;
255 int i;
256
257 for (i = 0; i < MAX_BPF_REG; i++) {
258 t = env->cur_state.regs[i].type;
259 if (t == NOT_INIT)
260 continue;
261 verbose(" R%d=%s", i, reg_type_str[t]);
262 if (t == CONST_IMM || t == PTR_TO_STACK)
263 verbose("%d", env->cur_state.regs[i].imm);
264 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
265 t == PTR_TO_MAP_VALUE_OR_NULL)
266 verbose("(ks=%d,vs=%d)",
267 env->cur_state.regs[i].map_ptr->key_size,
268 env->cur_state.regs[i].map_ptr->value_size);
269 }
270 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
271 if (env->cur_state.stack_slot_type[i] == STACK_SPILL)
272 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
273 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]);
274 }
275 verbose("\n");
276 }
277
278 static const char *const bpf_class_string[] = {
279 [BPF_LD] = "ld",
280 [BPF_LDX] = "ldx",
281 [BPF_ST] = "st",
282 [BPF_STX] = "stx",
283 [BPF_ALU] = "alu",
284 [BPF_JMP] = "jmp",
285 [BPF_RET] = "BUG",
286 [BPF_ALU64] = "alu64",
287 };
288
289 static const char *const bpf_alu_string[16] = {
290 [BPF_ADD >> 4] = "+=",
291 [BPF_SUB >> 4] = "-=",
292 [BPF_MUL >> 4] = "*=",
293 [BPF_DIV >> 4] = "/=",
294 [BPF_OR >> 4] = "|=",
295 [BPF_AND >> 4] = "&=",
296 [BPF_LSH >> 4] = "<<=",
297 [BPF_RSH >> 4] = ">>=",
298 [BPF_NEG >> 4] = "neg",
299 [BPF_MOD >> 4] = "%=",
300 [BPF_XOR >> 4] = "^=",
301 [BPF_MOV >> 4] = "=",
302 [BPF_ARSH >> 4] = "s>>=",
303 [BPF_END >> 4] = "endian",
304 };
305
306 static const char *const bpf_ldst_string[] = {
307 [BPF_W >> 3] = "u32",
308 [BPF_H >> 3] = "u16",
309 [BPF_B >> 3] = "u8",
310 [BPF_DW >> 3] = "u64",
311 };
312
313 static const char *const bpf_jmp_string[16] = {
314 [BPF_JA >> 4] = "jmp",
315 [BPF_JEQ >> 4] = "==",
316 [BPF_JGT >> 4] = ">",
317 [BPF_JGE >> 4] = ">=",
318 [BPF_JSET >> 4] = "&",
319 [BPF_JNE >> 4] = "!=",
320 [BPF_JSGT >> 4] = "s>",
321 [BPF_JSGE >> 4] = "s>=",
322 [BPF_CALL >> 4] = "call",
323 [BPF_EXIT >> 4] = "exit",
324 };
325
326 static void print_bpf_insn(struct bpf_insn *insn)
327 {
328 u8 class = BPF_CLASS(insn->code);
329
330 if (class == BPF_ALU || class == BPF_ALU64) {
331 if (BPF_SRC(insn->code) == BPF_X)
332 verbose("(%02x) %sr%d %s %sr%d\n",
333 insn->code, class == BPF_ALU ? "(u32) " : "",
334 insn->dst_reg,
335 bpf_alu_string[BPF_OP(insn->code) >> 4],
336 class == BPF_ALU ? "(u32) " : "",
337 insn->src_reg);
338 else
339 verbose("(%02x) %sr%d %s %s%d\n",
340 insn->code, class == BPF_ALU ? "(u32) " : "",
341 insn->dst_reg,
342 bpf_alu_string[BPF_OP(insn->code) >> 4],
343 class == BPF_ALU ? "(u32) " : "",
344 insn->imm);
345 } else if (class == BPF_STX) {
346 if (BPF_MODE(insn->code) == BPF_MEM)
347 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
348 insn->code,
349 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
350 insn->dst_reg,
351 insn->off, insn->src_reg);
352 else if (BPF_MODE(insn->code) == BPF_XADD)
353 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
354 insn->code,
355 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
356 insn->dst_reg, insn->off,
357 insn->src_reg);
358 else
359 verbose("BUG_%02x\n", insn->code);
360 } else if (class == BPF_ST) {
361 if (BPF_MODE(insn->code) != BPF_MEM) {
362 verbose("BUG_st_%02x\n", insn->code);
363 return;
364 }
365 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
366 insn->code,
367 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
368 insn->dst_reg,
369 insn->off, insn->imm);
370 } else if (class == BPF_LDX) {
371 if (BPF_MODE(insn->code) != BPF_MEM) {
372 verbose("BUG_ldx_%02x\n", insn->code);
373 return;
374 }
375 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
376 insn->code, insn->dst_reg,
377 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
378 insn->src_reg, insn->off);
379 } else if (class == BPF_LD) {
380 if (BPF_MODE(insn->code) == BPF_ABS) {
381 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
382 insn->code,
383 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
384 insn->imm);
385 } else if (BPF_MODE(insn->code) == BPF_IND) {
386 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
387 insn->code,
388 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
389 insn->src_reg, insn->imm);
390 } else if (BPF_MODE(insn->code) == BPF_IMM) {
391 verbose("(%02x) r%d = 0x%x\n",
392 insn->code, insn->dst_reg, insn->imm);
393 } else {
394 verbose("BUG_ld_%02x\n", insn->code);
395 return;
396 }
397 } else if (class == BPF_JMP) {
398 u8 opcode = BPF_OP(insn->code);
399
400 if (opcode == BPF_CALL) {
401 verbose("(%02x) call %d\n", insn->code, insn->imm);
402 } else if (insn->code == (BPF_JMP | BPF_JA)) {
403 verbose("(%02x) goto pc%+d\n",
404 insn->code, insn->off);
405 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
406 verbose("(%02x) exit\n", insn->code);
407 } else if (BPF_SRC(insn->code) == BPF_X) {
408 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
409 insn->code, insn->dst_reg,
410 bpf_jmp_string[BPF_OP(insn->code) >> 4],
411 insn->src_reg, insn->off);
412 } else {
413 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
414 insn->code, insn->dst_reg,
415 bpf_jmp_string[BPF_OP(insn->code) >> 4],
416 insn->imm, insn->off);
417 }
418 } else {
419 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
420 }
421 }
422
423 static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
424 {
425 struct verifier_stack_elem *elem;
426 int insn_idx;
427
428 if (env->head == NULL)
429 return -1;
430
431 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
432 insn_idx = env->head->insn_idx;
433 if (prev_insn_idx)
434 *prev_insn_idx = env->head->prev_insn_idx;
435 elem = env->head->next;
436 kfree(env->head);
437 env->head = elem;
438 env->stack_size--;
439 return insn_idx;
440 }
441
442 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
443 int prev_insn_idx)
444 {
445 struct verifier_stack_elem *elem;
446
447 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
448 if (!elem)
449 goto err;
450
451 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
452 elem->insn_idx = insn_idx;
453 elem->prev_insn_idx = prev_insn_idx;
454 elem->next = env->head;
455 env->head = elem;
456 env->stack_size++;
457 if (env->stack_size > 1024) {
458 verbose("BPF program is too complex\n");
459 goto err;
460 }
461 return &elem->st;
462 err:
463 /* pop all elements and return */
464 while (pop_stack(env, NULL) >= 0);
465 return NULL;
466 }
467
468 #define CALLER_SAVED_REGS 6
469 static const int caller_saved[CALLER_SAVED_REGS] = {
470 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
471 };
472
473 static void init_reg_state(struct reg_state *regs)
474 {
475 int i;
476
477 for (i = 0; i < MAX_BPF_REG; i++) {
478 regs[i].type = NOT_INIT;
479 regs[i].imm = 0;
480 regs[i].map_ptr = NULL;
481 }
482
483 /* frame pointer */
484 regs[BPF_REG_FP].type = FRAME_PTR;
485
486 /* 1st arg to a function */
487 regs[BPF_REG_1].type = PTR_TO_CTX;
488 }
489
490 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
491 {
492 BUG_ON(regno >= MAX_BPF_REG);
493 regs[regno].type = UNKNOWN_VALUE;
494 regs[regno].imm = 0;
495 regs[regno].map_ptr = NULL;
496 }
497
498 enum reg_arg_type {
499 SRC_OP, /* register is used as source operand */
500 DST_OP, /* register is used as destination operand */
501 DST_OP_NO_MARK /* same as above, check only, don't mark */
502 };
503
504 static int check_reg_arg(struct reg_state *regs, u32 regno,
505 enum reg_arg_type t)
506 {
507 if (regno >= MAX_BPF_REG) {
508 verbose("R%d is invalid\n", regno);
509 return -EINVAL;
510 }
511
512 if (t == SRC_OP) {
513 /* check whether register used as source operand can be read */
514 if (regs[regno].type == NOT_INIT) {
515 verbose("R%d !read_ok\n", regno);
516 return -EACCES;
517 }
518 } else {
519 /* check whether register used as dest operand can be written to */
520 if (regno == BPF_REG_FP) {
521 verbose("frame pointer is read only\n");
522 return -EACCES;
523 }
524 if (t == DST_OP)
525 mark_reg_unknown_value(regs, regno);
526 }
527 return 0;
528 }
529
530 static int bpf_size_to_bytes(int bpf_size)
531 {
532 if (bpf_size == BPF_W)
533 return 4;
534 else if (bpf_size == BPF_H)
535 return 2;
536 else if (bpf_size == BPF_B)
537 return 1;
538 else if (bpf_size == BPF_DW)
539 return 8;
540 else
541 return -EINVAL;
542 }
543
544 static bool is_spillable_regtype(enum bpf_reg_type type)
545 {
546 switch (type) {
547 case PTR_TO_MAP_VALUE:
548 case PTR_TO_MAP_VALUE_OR_NULL:
549 case PTR_TO_STACK:
550 case PTR_TO_CTX:
551 case FRAME_PTR:
552 case CONST_PTR_TO_MAP:
553 return true;
554 default:
555 return false;
556 }
557 }
558
559 /* check_stack_read/write functions track spill/fill of registers,
560 * stack boundary and alignment are checked in check_mem_access()
561 */
562 static int check_stack_write(struct verifier_state *state, int off, int size,
563 int value_regno)
564 {
565 int i;
566 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
567 * so it's aligned access and [off, off + size) are within stack limits
568 */
569
570 if (value_regno >= 0 &&
571 is_spillable_regtype(state->regs[value_regno].type)) {
572
573 /* register containing pointer is being spilled into stack */
574 if (size != BPF_REG_SIZE) {
575 verbose("invalid size of register spill\n");
576 return -EACCES;
577 }
578
579 /* save register state */
580 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
581 state->regs[value_regno];
582
583 for (i = 0; i < BPF_REG_SIZE; i++)
584 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
585 } else {
586 /* regular write of data into stack */
587 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
588 (struct reg_state) {};
589
590 for (i = 0; i < size; i++)
591 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
592 }
593 return 0;
594 }
595
596 static int check_stack_read(struct verifier_state *state, int off, int size,
597 int value_regno)
598 {
599 u8 *slot_type;
600 int i;
601
602 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
603
604 if (slot_type[0] == STACK_SPILL) {
605 if (size != BPF_REG_SIZE) {
606 verbose("invalid size of register spill\n");
607 return -EACCES;
608 }
609 for (i = 1; i < BPF_REG_SIZE; i++) {
610 if (slot_type[i] != STACK_SPILL) {
611 verbose("corrupted spill memory\n");
612 return -EACCES;
613 }
614 }
615
616 if (value_regno >= 0)
617 /* restore register state from stack */
618 state->regs[value_regno] =
619 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
620 return 0;
621 } else {
622 for (i = 0; i < size; i++) {
623 if (slot_type[i] != STACK_MISC) {
624 verbose("invalid read from stack off %d+%d size %d\n",
625 off, i, size);
626 return -EACCES;
627 }
628 }
629 if (value_regno >= 0)
630 /* have read misc data from the stack */
631 mark_reg_unknown_value(state->regs, value_regno);
632 return 0;
633 }
634 }
635
636 /* check read/write into map element returned by bpf_map_lookup_elem() */
637 static int check_map_access(struct verifier_env *env, u32 regno, int off,
638 int size)
639 {
640 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
641
642 if (off < 0 || off + size > map->value_size) {
643 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
644 map->value_size, off, size);
645 return -EACCES;
646 }
647 return 0;
648 }
649
650 /* check access to 'struct bpf_context' fields */
651 static int check_ctx_access(struct verifier_env *env, int off, int size,
652 enum bpf_access_type t)
653 {
654 if (env->prog->aux->ops->is_valid_access &&
655 env->prog->aux->ops->is_valid_access(off, size, t))
656 return 0;
657
658 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
659 return -EACCES;
660 }
661
662 static bool is_pointer_value(struct verifier_env *env, int regno)
663 {
664 if (env->allow_ptr_leaks)
665 return false;
666
667 switch (env->cur_state.regs[regno].type) {
668 case UNKNOWN_VALUE:
669 case CONST_IMM:
670 return false;
671 default:
672 return true;
673 }
674 }
675
676 /* check whether memory at (regno + off) is accessible for t = (read | write)
677 * if t==write, value_regno is a register which value is stored into memory
678 * if t==read, value_regno is a register which will receive the value from memory
679 * if t==write && value_regno==-1, some unknown value is stored into memory
680 * if t==read && value_regno==-1, don't care what we read from memory
681 */
682 static int check_mem_access(struct verifier_env *env, u32 regno, int off,
683 int bpf_size, enum bpf_access_type t,
684 int value_regno)
685 {
686 struct verifier_state *state = &env->cur_state;
687 int size, err = 0;
688
689 if (state->regs[regno].type == PTR_TO_STACK)
690 off += state->regs[regno].imm;
691
692 size = bpf_size_to_bytes(bpf_size);
693 if (size < 0)
694 return size;
695
696 if (off % size != 0) {
697 verbose("misaligned access off %d size %d\n", off, size);
698 return -EACCES;
699 }
700
701 if (state->regs[regno].type == PTR_TO_MAP_VALUE) {
702 if (t == BPF_WRITE && value_regno >= 0 &&
703 is_pointer_value(env, value_regno)) {
704 verbose("R%d leaks addr into map\n", value_regno);
705 return -EACCES;
706 }
707 err = check_map_access(env, regno, off, size);
708 if (!err && t == BPF_READ && value_regno >= 0)
709 mark_reg_unknown_value(state->regs, value_regno);
710
711 } else if (state->regs[regno].type == PTR_TO_CTX) {
712 if (t == BPF_WRITE && value_regno >= 0 &&
713 is_pointer_value(env, value_regno)) {
714 verbose("R%d leaks addr into ctx\n", value_regno);
715 return -EACCES;
716 }
717 err = check_ctx_access(env, off, size, t);
718 if (!err && t == BPF_READ && value_regno >= 0)
719 mark_reg_unknown_value(state->regs, value_regno);
720
721 } else if (state->regs[regno].type == FRAME_PTR ||
722 state->regs[regno].type == PTR_TO_STACK) {
723 if (off >= 0 || off < -MAX_BPF_STACK) {
724 verbose("invalid stack off=%d size=%d\n", off, size);
725 return -EACCES;
726 }
727 if (t == BPF_WRITE) {
728 if (!env->allow_ptr_leaks &&
729 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
730 size != BPF_REG_SIZE) {
731 verbose("attempt to corrupt spilled pointer on stack\n");
732 return -EACCES;
733 }
734 err = check_stack_write(state, off, size, value_regno);
735 } else {
736 err = check_stack_read(state, off, size, value_regno);
737 }
738 } else {
739 verbose("R%d invalid mem access '%s'\n",
740 regno, reg_type_str[state->regs[regno].type]);
741 return -EACCES;
742 }
743 return err;
744 }
745
746 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
747 {
748 struct reg_state *regs = env->cur_state.regs;
749 int err;
750
751 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
752 insn->imm != 0) {
753 verbose("BPF_XADD uses reserved fields\n");
754 return -EINVAL;
755 }
756
757 /* check src1 operand */
758 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
759 if (err)
760 return err;
761
762 /* check src2 operand */
763 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
764 if (err)
765 return err;
766
767 /* check whether atomic_add can read the memory */
768 err = check_mem_access(env, insn->dst_reg, insn->off,
769 BPF_SIZE(insn->code), BPF_READ, -1);
770 if (err)
771 return err;
772
773 /* check whether atomic_add can write into the same memory */
774 return check_mem_access(env, insn->dst_reg, insn->off,
775 BPF_SIZE(insn->code), BPF_WRITE, -1);
776 }
777
778 /* when register 'regno' is passed into function that will read 'access_size'
779 * bytes from that pointer, make sure that it's within stack boundary
780 * and all elements of stack are initialized
781 */
782 static int check_stack_boundary(struct verifier_env *env, int regno,
783 int access_size, bool zero_size_allowed)
784 {
785 struct verifier_state *state = &env->cur_state;
786 struct reg_state *regs = state->regs;
787 int off, i;
788
789 if (regs[regno].type != PTR_TO_STACK) {
790 if (zero_size_allowed && access_size == 0 &&
791 regs[regno].type == CONST_IMM &&
792 regs[regno].imm == 0)
793 return 0;
794
795 verbose("R%d type=%s expected=%s\n", regno,
796 reg_type_str[regs[regno].type],
797 reg_type_str[PTR_TO_STACK]);
798 return -EACCES;
799 }
800
801 off = regs[regno].imm;
802 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
803 access_size <= 0) {
804 verbose("invalid stack type R%d off=%d access_size=%d\n",
805 regno, off, access_size);
806 return -EACCES;
807 }
808
809 for (i = 0; i < access_size; i++) {
810 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
811 verbose("invalid indirect read from stack off %d+%d size %d\n",
812 off, i, access_size);
813 return -EACCES;
814 }
815 }
816 return 0;
817 }
818
819 static int check_func_arg(struct verifier_env *env, u32 regno,
820 enum bpf_arg_type arg_type, struct bpf_map **mapp)
821 {
822 struct reg_state *reg = env->cur_state.regs + regno;
823 enum bpf_reg_type expected_type;
824 int err = 0;
825
826 if (arg_type == ARG_DONTCARE)
827 return 0;
828
829 if (reg->type == NOT_INIT) {
830 verbose("R%d !read_ok\n", regno);
831 return -EACCES;
832 }
833
834 if (arg_type == ARG_ANYTHING) {
835 if (is_pointer_value(env, regno)) {
836 verbose("R%d leaks addr into helper function\n", regno);
837 return -EACCES;
838 }
839 return 0;
840 }
841
842 if (arg_type == ARG_PTR_TO_MAP_KEY ||
843 arg_type == ARG_PTR_TO_MAP_VALUE) {
844 expected_type = PTR_TO_STACK;
845 } else if (arg_type == ARG_CONST_STACK_SIZE ||
846 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
847 expected_type = CONST_IMM;
848 } else if (arg_type == ARG_CONST_MAP_PTR) {
849 expected_type = CONST_PTR_TO_MAP;
850 } else if (arg_type == ARG_PTR_TO_CTX) {
851 expected_type = PTR_TO_CTX;
852 } else if (arg_type == ARG_PTR_TO_STACK) {
853 expected_type = PTR_TO_STACK;
854 /* One exception here. In case function allows for NULL to be
855 * passed in as argument, it's a CONST_IMM type. Final test
856 * happens during stack boundary checking.
857 */
858 if (reg->type == CONST_IMM && reg->imm == 0)
859 expected_type = CONST_IMM;
860 } else {
861 verbose("unsupported arg_type %d\n", arg_type);
862 return -EFAULT;
863 }
864
865 if (reg->type != expected_type) {
866 verbose("R%d type=%s expected=%s\n", regno,
867 reg_type_str[reg->type], reg_type_str[expected_type]);
868 return -EACCES;
869 }
870
871 if (arg_type == ARG_CONST_MAP_PTR) {
872 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
873 *mapp = reg->map_ptr;
874
875 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
876 /* bpf_map_xxx(..., map_ptr, ..., key) call:
877 * check that [key, key + map->key_size) are within
878 * stack limits and initialized
879 */
880 if (!*mapp) {
881 /* in function declaration map_ptr must come before
882 * map_key, so that it's verified and known before
883 * we have to check map_key here. Otherwise it means
884 * that kernel subsystem misconfigured verifier
885 */
886 verbose("invalid map_ptr to access map->key\n");
887 return -EACCES;
888 }
889 err = check_stack_boundary(env, regno, (*mapp)->key_size,
890 false);
891 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
892 /* bpf_map_xxx(..., map_ptr, ..., value) call:
893 * check [value, value + map->value_size) validity
894 */
895 if (!*mapp) {
896 /* kernel subsystem misconfigured verifier */
897 verbose("invalid map_ptr to access map->value\n");
898 return -EACCES;
899 }
900 err = check_stack_boundary(env, regno, (*mapp)->value_size,
901 false);
902 } else if (arg_type == ARG_CONST_STACK_SIZE ||
903 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
904 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
905
906 /* bpf_xxx(..., buf, len) call will access 'len' bytes
907 * from stack pointer 'buf'. Check it
908 * note: regno == len, regno - 1 == buf
909 */
910 if (regno == 0) {
911 /* kernel subsystem misconfigured verifier */
912 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
913 return -EACCES;
914 }
915 err = check_stack_boundary(env, regno - 1, reg->imm,
916 zero_size_allowed);
917 }
918
919 return err;
920 }
921
922 static int check_map_func_compatibility(struct bpf_map *map, int func_id)
923 {
924 bool bool_map, bool_func;
925 int i;
926
927 if (!map)
928 return 0;
929
930 for (i = 0; i < ARRAY_SIZE(func_limit); i++) {
931 bool_map = (map->map_type == func_limit[i].map_type);
932 bool_func = (func_id == func_limit[i].func_id);
933 /* only when map & func pair match it can continue.
934 * don't allow any other map type to be passed into
935 * the special func;
936 */
937 if (bool_func && bool_map != bool_func) {
938 verbose("cannot pass map_type %d into func %d\n",
939 map->map_type, func_id);
940 return -EINVAL;
941 }
942 }
943
944 return 0;
945 }
946
947 static int check_call(struct verifier_env *env, int func_id)
948 {
949 struct verifier_state *state = &env->cur_state;
950 const struct bpf_func_proto *fn = NULL;
951 struct reg_state *regs = state->regs;
952 struct bpf_map *map = NULL;
953 struct reg_state *reg;
954 int i, err;
955
956 /* find function prototype */
957 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
958 verbose("invalid func %d\n", func_id);
959 return -EINVAL;
960 }
961
962 if (env->prog->aux->ops->get_func_proto)
963 fn = env->prog->aux->ops->get_func_proto(func_id);
964
965 if (!fn) {
966 verbose("unknown func %d\n", func_id);
967 return -EINVAL;
968 }
969
970 /* eBPF programs must be GPL compatible to use GPL-ed functions */
971 if (!env->prog->gpl_compatible && fn->gpl_only) {
972 verbose("cannot call GPL only function from proprietary program\n");
973 return -EINVAL;
974 }
975
976 /* check args */
977 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map);
978 if (err)
979 return err;
980 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map);
981 if (err)
982 return err;
983 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map);
984 if (err)
985 return err;
986 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map);
987 if (err)
988 return err;
989 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map);
990 if (err)
991 return err;
992
993 /* reset caller saved regs */
994 for (i = 0; i < CALLER_SAVED_REGS; i++) {
995 reg = regs + caller_saved[i];
996 reg->type = NOT_INIT;
997 reg->imm = 0;
998 }
999
1000 /* update return register */
1001 if (fn->ret_type == RET_INTEGER) {
1002 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1003 } else if (fn->ret_type == RET_VOID) {
1004 regs[BPF_REG_0].type = NOT_INIT;
1005 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
1006 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
1007 /* remember map_ptr, so that check_map_access()
1008 * can check 'value_size' boundary of memory access
1009 * to map element returned from bpf_map_lookup_elem()
1010 */
1011 if (map == NULL) {
1012 verbose("kernel subsystem misconfigured verifier\n");
1013 return -EINVAL;
1014 }
1015 regs[BPF_REG_0].map_ptr = map;
1016 } else {
1017 verbose("unknown return type %d of func %d\n",
1018 fn->ret_type, func_id);
1019 return -EINVAL;
1020 }
1021
1022 err = check_map_func_compatibility(map, func_id);
1023 if (err)
1024 return err;
1025
1026 return 0;
1027 }
1028
1029 /* check validity of 32-bit and 64-bit arithmetic operations */
1030 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn)
1031 {
1032 struct reg_state *regs = env->cur_state.regs;
1033 u8 opcode = BPF_OP(insn->code);
1034 int err;
1035
1036 if (opcode == BPF_END || opcode == BPF_NEG) {
1037 if (opcode == BPF_NEG) {
1038 if (BPF_SRC(insn->code) != 0 ||
1039 insn->src_reg != BPF_REG_0 ||
1040 insn->off != 0 || insn->imm != 0) {
1041 verbose("BPF_NEG uses reserved fields\n");
1042 return -EINVAL;
1043 }
1044 } else {
1045 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1046 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1047 verbose("BPF_END uses reserved fields\n");
1048 return -EINVAL;
1049 }
1050 }
1051
1052 /* check src operand */
1053 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1054 if (err)
1055 return err;
1056
1057 if (is_pointer_value(env, insn->dst_reg)) {
1058 verbose("R%d pointer arithmetic prohibited\n",
1059 insn->dst_reg);
1060 return -EACCES;
1061 }
1062
1063 /* check dest operand */
1064 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1065 if (err)
1066 return err;
1067
1068 } else if (opcode == BPF_MOV) {
1069
1070 if (BPF_SRC(insn->code) == BPF_X) {
1071 if (insn->imm != 0 || insn->off != 0) {
1072 verbose("BPF_MOV uses reserved fields\n");
1073 return -EINVAL;
1074 }
1075
1076 /* check src operand */
1077 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1078 if (err)
1079 return err;
1080 } else {
1081 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1082 verbose("BPF_MOV uses reserved fields\n");
1083 return -EINVAL;
1084 }
1085 }
1086
1087 /* check dest operand */
1088 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1089 if (err)
1090 return err;
1091
1092 if (BPF_SRC(insn->code) == BPF_X) {
1093 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1094 /* case: R1 = R2
1095 * copy register state to dest reg
1096 */
1097 regs[insn->dst_reg] = regs[insn->src_reg];
1098 } else {
1099 if (is_pointer_value(env, insn->src_reg)) {
1100 verbose("R%d partial copy of pointer\n",
1101 insn->src_reg);
1102 return -EACCES;
1103 }
1104 regs[insn->dst_reg].type = UNKNOWN_VALUE;
1105 regs[insn->dst_reg].map_ptr = NULL;
1106 }
1107 } else {
1108 /* case: R = imm
1109 * remember the value we stored into this reg
1110 */
1111 regs[insn->dst_reg].type = CONST_IMM;
1112 regs[insn->dst_reg].imm = insn->imm;
1113 }
1114
1115 } else if (opcode > BPF_END) {
1116 verbose("invalid BPF_ALU opcode %x\n", opcode);
1117 return -EINVAL;
1118
1119 } else { /* all other ALU ops: and, sub, xor, add, ... */
1120
1121 bool stack_relative = false;
1122
1123 if (BPF_SRC(insn->code) == BPF_X) {
1124 if (insn->imm != 0 || insn->off != 0) {
1125 verbose("BPF_ALU uses reserved fields\n");
1126 return -EINVAL;
1127 }
1128 /* check src1 operand */
1129 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1130 if (err)
1131 return err;
1132 } else {
1133 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1134 verbose("BPF_ALU uses reserved fields\n");
1135 return -EINVAL;
1136 }
1137 }
1138
1139 /* check src2 operand */
1140 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1141 if (err)
1142 return err;
1143
1144 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1145 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1146 verbose("div by zero\n");
1147 return -EINVAL;
1148 }
1149
1150 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1151 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1152 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1153
1154 if (insn->imm < 0 || insn->imm >= size) {
1155 verbose("invalid shift %d\n", insn->imm);
1156 return -EINVAL;
1157 }
1158 }
1159
1160 /* pattern match 'bpf_add Rx, imm' instruction */
1161 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1162 regs[insn->dst_reg].type == FRAME_PTR &&
1163 BPF_SRC(insn->code) == BPF_K) {
1164 stack_relative = true;
1165 } else if (is_pointer_value(env, insn->dst_reg)) {
1166 verbose("R%d pointer arithmetic prohibited\n",
1167 insn->dst_reg);
1168 return -EACCES;
1169 } else if (BPF_SRC(insn->code) == BPF_X &&
1170 is_pointer_value(env, insn->src_reg)) {
1171 verbose("R%d pointer arithmetic prohibited\n",
1172 insn->src_reg);
1173 return -EACCES;
1174 }
1175
1176 /* check dest operand */
1177 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1178 if (err)
1179 return err;
1180
1181 if (stack_relative) {
1182 regs[insn->dst_reg].type = PTR_TO_STACK;
1183 regs[insn->dst_reg].imm = insn->imm;
1184 }
1185 }
1186
1187 return 0;
1188 }
1189
1190 static int check_cond_jmp_op(struct verifier_env *env,
1191 struct bpf_insn *insn, int *insn_idx)
1192 {
1193 struct reg_state *regs = env->cur_state.regs;
1194 struct verifier_state *other_branch;
1195 u8 opcode = BPF_OP(insn->code);
1196 int err;
1197
1198 if (opcode > BPF_EXIT) {
1199 verbose("invalid BPF_JMP opcode %x\n", opcode);
1200 return -EINVAL;
1201 }
1202
1203 if (BPF_SRC(insn->code) == BPF_X) {
1204 if (insn->imm != 0) {
1205 verbose("BPF_JMP uses reserved fields\n");
1206 return -EINVAL;
1207 }
1208
1209 /* check src1 operand */
1210 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1211 if (err)
1212 return err;
1213
1214 if (is_pointer_value(env, insn->src_reg)) {
1215 verbose("R%d pointer comparison prohibited\n",
1216 insn->src_reg);
1217 return -EACCES;
1218 }
1219 } else {
1220 if (insn->src_reg != BPF_REG_0) {
1221 verbose("BPF_JMP uses reserved fields\n");
1222 return -EINVAL;
1223 }
1224 }
1225
1226 /* check src2 operand */
1227 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1228 if (err)
1229 return err;
1230
1231 /* detect if R == 0 where R was initialized to zero earlier */
1232 if (BPF_SRC(insn->code) == BPF_K &&
1233 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1234 regs[insn->dst_reg].type == CONST_IMM &&
1235 regs[insn->dst_reg].imm == insn->imm) {
1236 if (opcode == BPF_JEQ) {
1237 /* if (imm == imm) goto pc+off;
1238 * only follow the goto, ignore fall-through
1239 */
1240 *insn_idx += insn->off;
1241 return 0;
1242 } else {
1243 /* if (imm != imm) goto pc+off;
1244 * only follow fall-through branch, since
1245 * that's where the program will go
1246 */
1247 return 0;
1248 }
1249 }
1250
1251 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1252 if (!other_branch)
1253 return -EFAULT;
1254
1255 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1256 if (BPF_SRC(insn->code) == BPF_K &&
1257 insn->imm == 0 && (opcode == BPF_JEQ ||
1258 opcode == BPF_JNE) &&
1259 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1260 if (opcode == BPF_JEQ) {
1261 /* next fallthrough insn can access memory via
1262 * this register
1263 */
1264 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1265 /* branch targer cannot access it, since reg == 0 */
1266 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1267 other_branch->regs[insn->dst_reg].imm = 0;
1268 } else {
1269 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1270 regs[insn->dst_reg].type = CONST_IMM;
1271 regs[insn->dst_reg].imm = 0;
1272 }
1273 } else if (is_pointer_value(env, insn->dst_reg)) {
1274 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
1275 return -EACCES;
1276 } else if (BPF_SRC(insn->code) == BPF_K &&
1277 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1278
1279 if (opcode == BPF_JEQ) {
1280 /* detect if (R == imm) goto
1281 * and in the target state recognize that R = imm
1282 */
1283 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1284 other_branch->regs[insn->dst_reg].imm = insn->imm;
1285 } else {
1286 /* detect if (R != imm) goto
1287 * and in the fall-through state recognize that R = imm
1288 */
1289 regs[insn->dst_reg].type = CONST_IMM;
1290 regs[insn->dst_reg].imm = insn->imm;
1291 }
1292 }
1293 if (log_level)
1294 print_verifier_state(env);
1295 return 0;
1296 }
1297
1298 /* return the map pointer stored inside BPF_LD_IMM64 instruction */
1299 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1300 {
1301 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1302
1303 return (struct bpf_map *) (unsigned long) imm64;
1304 }
1305
1306 /* verify BPF_LD_IMM64 instruction */
1307 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1308 {
1309 struct reg_state *regs = env->cur_state.regs;
1310 int err;
1311
1312 if (BPF_SIZE(insn->code) != BPF_DW) {
1313 verbose("invalid BPF_LD_IMM insn\n");
1314 return -EINVAL;
1315 }
1316 if (insn->off != 0) {
1317 verbose("BPF_LD_IMM64 uses reserved fields\n");
1318 return -EINVAL;
1319 }
1320
1321 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1322 if (err)
1323 return err;
1324
1325 if (insn->src_reg == 0)
1326 /* generic move 64-bit immediate into a register */
1327 return 0;
1328
1329 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1330 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1331
1332 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1333 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1334 return 0;
1335 }
1336
1337 static bool may_access_skb(enum bpf_prog_type type)
1338 {
1339 switch (type) {
1340 case BPF_PROG_TYPE_SOCKET_FILTER:
1341 case BPF_PROG_TYPE_SCHED_CLS:
1342 case BPF_PROG_TYPE_SCHED_ACT:
1343 return true;
1344 default:
1345 return false;
1346 }
1347 }
1348
1349 /* verify safety of LD_ABS|LD_IND instructions:
1350 * - they can only appear in the programs where ctx == skb
1351 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1352 * preserve R6-R9, and store return value into R0
1353 *
1354 * Implicit input:
1355 * ctx == skb == R6 == CTX
1356 *
1357 * Explicit input:
1358 * SRC == any register
1359 * IMM == 32-bit immediate
1360 *
1361 * Output:
1362 * R0 - 8/16/32-bit skb data converted to cpu endianness
1363 */
1364 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1365 {
1366 struct reg_state *regs = env->cur_state.regs;
1367 u8 mode = BPF_MODE(insn->code);
1368 struct reg_state *reg;
1369 int i, err;
1370
1371 if (!may_access_skb(env->prog->type)) {
1372 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n");
1373 return -EINVAL;
1374 }
1375
1376 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1377 BPF_SIZE(insn->code) == BPF_DW ||
1378 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1379 verbose("BPF_LD_ABS uses reserved fields\n");
1380 return -EINVAL;
1381 }
1382
1383 /* check whether implicit source operand (register R6) is readable */
1384 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1385 if (err)
1386 return err;
1387
1388 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1389 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1390 return -EINVAL;
1391 }
1392
1393 if (mode == BPF_IND) {
1394 /* check explicit source operand */
1395 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1396 if (err)
1397 return err;
1398 }
1399
1400 /* reset caller saved regs to unreadable */
1401 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1402 reg = regs + caller_saved[i];
1403 reg->type = NOT_INIT;
1404 reg->imm = 0;
1405 }
1406
1407 /* mark destination R0 register as readable, since it contains
1408 * the value fetched from the packet
1409 */
1410 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1411 return 0;
1412 }
1413
1414 /* non-recursive DFS pseudo code
1415 * 1 procedure DFS-iterative(G,v):
1416 * 2 label v as discovered
1417 * 3 let S be a stack
1418 * 4 S.push(v)
1419 * 5 while S is not empty
1420 * 6 t <- S.pop()
1421 * 7 if t is what we're looking for:
1422 * 8 return t
1423 * 9 for all edges e in G.adjacentEdges(t) do
1424 * 10 if edge e is already labelled
1425 * 11 continue with the next edge
1426 * 12 w <- G.adjacentVertex(t,e)
1427 * 13 if vertex w is not discovered and not explored
1428 * 14 label e as tree-edge
1429 * 15 label w as discovered
1430 * 16 S.push(w)
1431 * 17 continue at 5
1432 * 18 else if vertex w is discovered
1433 * 19 label e as back-edge
1434 * 20 else
1435 * 21 // vertex w is explored
1436 * 22 label e as forward- or cross-edge
1437 * 23 label t as explored
1438 * 24 S.pop()
1439 *
1440 * convention:
1441 * 0x10 - discovered
1442 * 0x11 - discovered and fall-through edge labelled
1443 * 0x12 - discovered and fall-through and branch edges labelled
1444 * 0x20 - explored
1445 */
1446
1447 enum {
1448 DISCOVERED = 0x10,
1449 EXPLORED = 0x20,
1450 FALLTHROUGH = 1,
1451 BRANCH = 2,
1452 };
1453
1454 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1455
1456 static int *insn_stack; /* stack of insns to process */
1457 static int cur_stack; /* current stack index */
1458 static int *insn_state;
1459
1460 /* t, w, e - match pseudo-code above:
1461 * t - index of current instruction
1462 * w - next instruction
1463 * e - edge
1464 */
1465 static int push_insn(int t, int w, int e, struct verifier_env *env)
1466 {
1467 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1468 return 0;
1469
1470 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1471 return 0;
1472
1473 if (w < 0 || w >= env->prog->len) {
1474 verbose("jump out of range from insn %d to %d\n", t, w);
1475 return -EINVAL;
1476 }
1477
1478 if (e == BRANCH)
1479 /* mark branch target for state pruning */
1480 env->explored_states[w] = STATE_LIST_MARK;
1481
1482 if (insn_state[w] == 0) {
1483 /* tree-edge */
1484 insn_state[t] = DISCOVERED | e;
1485 insn_state[w] = DISCOVERED;
1486 if (cur_stack >= env->prog->len)
1487 return -E2BIG;
1488 insn_stack[cur_stack++] = w;
1489 return 1;
1490 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1491 verbose("back-edge from insn %d to %d\n", t, w);
1492 return -EINVAL;
1493 } else if (insn_state[w] == EXPLORED) {
1494 /* forward- or cross-edge */
1495 insn_state[t] = DISCOVERED | e;
1496 } else {
1497 verbose("insn state internal bug\n");
1498 return -EFAULT;
1499 }
1500 return 0;
1501 }
1502
1503 /* non-recursive depth-first-search to detect loops in BPF program
1504 * loop == back-edge in directed graph
1505 */
1506 static int check_cfg(struct verifier_env *env)
1507 {
1508 struct bpf_insn *insns = env->prog->insnsi;
1509 int insn_cnt = env->prog->len;
1510 int ret = 0;
1511 int i, t;
1512
1513 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1514 if (!insn_state)
1515 return -ENOMEM;
1516
1517 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1518 if (!insn_stack) {
1519 kfree(insn_state);
1520 return -ENOMEM;
1521 }
1522
1523 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1524 insn_stack[0] = 0; /* 0 is the first instruction */
1525 cur_stack = 1;
1526
1527 peek_stack:
1528 if (cur_stack == 0)
1529 goto check_state;
1530 t = insn_stack[cur_stack - 1];
1531
1532 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1533 u8 opcode = BPF_OP(insns[t].code);
1534
1535 if (opcode == BPF_EXIT) {
1536 goto mark_explored;
1537 } else if (opcode == BPF_CALL) {
1538 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1539 if (ret == 1)
1540 goto peek_stack;
1541 else if (ret < 0)
1542 goto err_free;
1543 } else if (opcode == BPF_JA) {
1544 if (BPF_SRC(insns[t].code) != BPF_K) {
1545 ret = -EINVAL;
1546 goto err_free;
1547 }
1548 /* unconditional jump with single edge */
1549 ret = push_insn(t, t + insns[t].off + 1,
1550 FALLTHROUGH, env);
1551 if (ret == 1)
1552 goto peek_stack;
1553 else if (ret < 0)
1554 goto err_free;
1555 /* tell verifier to check for equivalent states
1556 * after every call and jump
1557 */
1558 if (t + 1 < insn_cnt)
1559 env->explored_states[t + 1] = STATE_LIST_MARK;
1560 } else {
1561 /* conditional jump with two edges */
1562 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1563 if (ret == 1)
1564 goto peek_stack;
1565 else if (ret < 0)
1566 goto err_free;
1567
1568 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1569 if (ret == 1)
1570 goto peek_stack;
1571 else if (ret < 0)
1572 goto err_free;
1573 }
1574 } else {
1575 /* all other non-branch instructions with single
1576 * fall-through edge
1577 */
1578 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1579 if (ret == 1)
1580 goto peek_stack;
1581 else if (ret < 0)
1582 goto err_free;
1583 }
1584
1585 mark_explored:
1586 insn_state[t] = EXPLORED;
1587 if (cur_stack-- <= 0) {
1588 verbose("pop stack internal bug\n");
1589 ret = -EFAULT;
1590 goto err_free;
1591 }
1592 goto peek_stack;
1593
1594 check_state:
1595 for (i = 0; i < insn_cnt; i++) {
1596 if (insn_state[i] != EXPLORED) {
1597 verbose("unreachable insn %d\n", i);
1598 ret = -EINVAL;
1599 goto err_free;
1600 }
1601 }
1602 ret = 0; /* cfg looks good */
1603
1604 err_free:
1605 kfree(insn_state);
1606 kfree(insn_stack);
1607 return ret;
1608 }
1609
1610 /* compare two verifier states
1611 *
1612 * all states stored in state_list are known to be valid, since
1613 * verifier reached 'bpf_exit' instruction through them
1614 *
1615 * this function is called when verifier exploring different branches of
1616 * execution popped from the state stack. If it sees an old state that has
1617 * more strict register state and more strict stack state then this execution
1618 * branch doesn't need to be explored further, since verifier already
1619 * concluded that more strict state leads to valid finish.
1620 *
1621 * Therefore two states are equivalent if register state is more conservative
1622 * and explored stack state is more conservative than the current one.
1623 * Example:
1624 * explored current
1625 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1626 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1627 *
1628 * In other words if current stack state (one being explored) has more
1629 * valid slots than old one that already passed validation, it means
1630 * the verifier can stop exploring and conclude that current state is valid too
1631 *
1632 * Similarly with registers. If explored state has register type as invalid
1633 * whereas register type in current state is meaningful, it means that
1634 * the current state will reach 'bpf_exit' instruction safely
1635 */
1636 static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1637 {
1638 int i;
1639
1640 for (i = 0; i < MAX_BPF_REG; i++) {
1641 if (memcmp(&old->regs[i], &cur->regs[i],
1642 sizeof(old->regs[0])) != 0) {
1643 if (old->regs[i].type == NOT_INIT ||
1644 (old->regs[i].type == UNKNOWN_VALUE &&
1645 cur->regs[i].type != NOT_INIT))
1646 continue;
1647 return false;
1648 }
1649 }
1650
1651 for (i = 0; i < MAX_BPF_STACK; i++) {
1652 if (old->stack_slot_type[i] == STACK_INVALID)
1653 continue;
1654 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1655 /* Ex: old explored (safe) state has STACK_SPILL in
1656 * this stack slot, but current has has STACK_MISC ->
1657 * this verifier states are not equivalent,
1658 * return false to continue verification of this path
1659 */
1660 return false;
1661 if (i % BPF_REG_SIZE)
1662 continue;
1663 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1664 &cur->spilled_regs[i / BPF_REG_SIZE],
1665 sizeof(old->spilled_regs[0])))
1666 /* when explored and current stack slot types are
1667 * the same, check that stored pointers types
1668 * are the same as well.
1669 * Ex: explored safe path could have stored
1670 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1671 * but current path has stored:
1672 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1673 * such verifier states are not equivalent.
1674 * return false to continue verification of this path
1675 */
1676 return false;
1677 else
1678 continue;
1679 }
1680 return true;
1681 }
1682
1683 static int is_state_visited(struct verifier_env *env, int insn_idx)
1684 {
1685 struct verifier_state_list *new_sl;
1686 struct verifier_state_list *sl;
1687
1688 sl = env->explored_states[insn_idx];
1689 if (!sl)
1690 /* this 'insn_idx' instruction wasn't marked, so we will not
1691 * be doing state search here
1692 */
1693 return 0;
1694
1695 while (sl != STATE_LIST_MARK) {
1696 if (states_equal(&sl->state, &env->cur_state))
1697 /* reached equivalent register/stack state,
1698 * prune the search
1699 */
1700 return 1;
1701 sl = sl->next;
1702 }
1703
1704 /* there were no equivalent states, remember current one.
1705 * technically the current state is not proven to be safe yet,
1706 * but it will either reach bpf_exit (which means it's safe) or
1707 * it will be rejected. Since there are no loops, we won't be
1708 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1709 */
1710 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1711 if (!new_sl)
1712 return -ENOMEM;
1713
1714 /* add new state to the head of linked list */
1715 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1716 new_sl->next = env->explored_states[insn_idx];
1717 env->explored_states[insn_idx] = new_sl;
1718 return 0;
1719 }
1720
1721 static int do_check(struct verifier_env *env)
1722 {
1723 struct verifier_state *state = &env->cur_state;
1724 struct bpf_insn *insns = env->prog->insnsi;
1725 struct reg_state *regs = state->regs;
1726 int insn_cnt = env->prog->len;
1727 int insn_idx, prev_insn_idx = 0;
1728 int insn_processed = 0;
1729 bool do_print_state = false;
1730
1731 init_reg_state(regs);
1732 insn_idx = 0;
1733 for (;;) {
1734 struct bpf_insn *insn;
1735 u8 class;
1736 int err;
1737
1738 if (insn_idx >= insn_cnt) {
1739 verbose("invalid insn idx %d insn_cnt %d\n",
1740 insn_idx, insn_cnt);
1741 return -EFAULT;
1742 }
1743
1744 insn = &insns[insn_idx];
1745 class = BPF_CLASS(insn->code);
1746
1747 if (++insn_processed > 32768) {
1748 verbose("BPF program is too large. Proccessed %d insn\n",
1749 insn_processed);
1750 return -E2BIG;
1751 }
1752
1753 err = is_state_visited(env, insn_idx);
1754 if (err < 0)
1755 return err;
1756 if (err == 1) {
1757 /* found equivalent state, can prune the search */
1758 if (log_level) {
1759 if (do_print_state)
1760 verbose("\nfrom %d to %d: safe\n",
1761 prev_insn_idx, insn_idx);
1762 else
1763 verbose("%d: safe\n", insn_idx);
1764 }
1765 goto process_bpf_exit;
1766 }
1767
1768 if (log_level && do_print_state) {
1769 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1770 print_verifier_state(env);
1771 do_print_state = false;
1772 }
1773
1774 if (log_level) {
1775 verbose("%d: ", insn_idx);
1776 print_bpf_insn(insn);
1777 }
1778
1779 if (class == BPF_ALU || class == BPF_ALU64) {
1780 err = check_alu_op(env, insn);
1781 if (err)
1782 return err;
1783
1784 } else if (class == BPF_LDX) {
1785 enum bpf_reg_type src_reg_type;
1786
1787 /* check for reserved fields is already done */
1788
1789 /* check src operand */
1790 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1791 if (err)
1792 return err;
1793
1794 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1795 if (err)
1796 return err;
1797
1798 src_reg_type = regs[insn->src_reg].type;
1799
1800 /* check that memory (src_reg + off) is readable,
1801 * the state of dst_reg will be updated by this func
1802 */
1803 err = check_mem_access(env, insn->src_reg, insn->off,
1804 BPF_SIZE(insn->code), BPF_READ,
1805 insn->dst_reg);
1806 if (err)
1807 return err;
1808
1809 if (BPF_SIZE(insn->code) != BPF_W) {
1810 insn_idx++;
1811 continue;
1812 }
1813
1814 if (insn->imm == 0) {
1815 /* saw a valid insn
1816 * dst_reg = *(u32 *)(src_reg + off)
1817 * use reserved 'imm' field to mark this insn
1818 */
1819 insn->imm = src_reg_type;
1820
1821 } else if (src_reg_type != insn->imm &&
1822 (src_reg_type == PTR_TO_CTX ||
1823 insn->imm == PTR_TO_CTX)) {
1824 /* ABuser program is trying to use the same insn
1825 * dst_reg = *(u32*) (src_reg + off)
1826 * with different pointer types:
1827 * src_reg == ctx in one branch and
1828 * src_reg == stack|map in some other branch.
1829 * Reject it.
1830 */
1831 verbose("same insn cannot be used with different pointers\n");
1832 return -EINVAL;
1833 }
1834
1835 } else if (class == BPF_STX) {
1836 enum bpf_reg_type dst_reg_type;
1837
1838 if (BPF_MODE(insn->code) == BPF_XADD) {
1839 err = check_xadd(env, insn);
1840 if (err)
1841 return err;
1842 insn_idx++;
1843 continue;
1844 }
1845
1846 /* check src1 operand */
1847 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1848 if (err)
1849 return err;
1850 /* check src2 operand */
1851 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1852 if (err)
1853 return err;
1854
1855 dst_reg_type = regs[insn->dst_reg].type;
1856
1857 /* check that memory (dst_reg + off) is writeable */
1858 err = check_mem_access(env, insn->dst_reg, insn->off,
1859 BPF_SIZE(insn->code), BPF_WRITE,
1860 insn->src_reg);
1861 if (err)
1862 return err;
1863
1864 if (insn->imm == 0) {
1865 insn->imm = dst_reg_type;
1866 } else if (dst_reg_type != insn->imm &&
1867 (dst_reg_type == PTR_TO_CTX ||
1868 insn->imm == PTR_TO_CTX)) {
1869 verbose("same insn cannot be used with different pointers\n");
1870 return -EINVAL;
1871 }
1872
1873 } else if (class == BPF_ST) {
1874 if (BPF_MODE(insn->code) != BPF_MEM ||
1875 insn->src_reg != BPF_REG_0) {
1876 verbose("BPF_ST uses reserved fields\n");
1877 return -EINVAL;
1878 }
1879 /* check src operand */
1880 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1881 if (err)
1882 return err;
1883
1884 /* check that memory (dst_reg + off) is writeable */
1885 err = check_mem_access(env, insn->dst_reg, insn->off,
1886 BPF_SIZE(insn->code), BPF_WRITE,
1887 -1);
1888 if (err)
1889 return err;
1890
1891 } else if (class == BPF_JMP) {
1892 u8 opcode = BPF_OP(insn->code);
1893
1894 if (opcode == BPF_CALL) {
1895 if (BPF_SRC(insn->code) != BPF_K ||
1896 insn->off != 0 ||
1897 insn->src_reg != BPF_REG_0 ||
1898 insn->dst_reg != BPF_REG_0) {
1899 verbose("BPF_CALL uses reserved fields\n");
1900 return -EINVAL;
1901 }
1902
1903 err = check_call(env, insn->imm);
1904 if (err)
1905 return err;
1906
1907 } else if (opcode == BPF_JA) {
1908 if (BPF_SRC(insn->code) != BPF_K ||
1909 insn->imm != 0 ||
1910 insn->src_reg != BPF_REG_0 ||
1911 insn->dst_reg != BPF_REG_0) {
1912 verbose("BPF_JA uses reserved fields\n");
1913 return -EINVAL;
1914 }
1915
1916 insn_idx += insn->off + 1;
1917 continue;
1918
1919 } else if (opcode == BPF_EXIT) {
1920 if (BPF_SRC(insn->code) != BPF_K ||
1921 insn->imm != 0 ||
1922 insn->src_reg != BPF_REG_0 ||
1923 insn->dst_reg != BPF_REG_0) {
1924 verbose("BPF_EXIT uses reserved fields\n");
1925 return -EINVAL;
1926 }
1927
1928 /* eBPF calling convetion is such that R0 is used
1929 * to return the value from eBPF program.
1930 * Make sure that it's readable at this time
1931 * of bpf_exit, which means that program wrote
1932 * something into it earlier
1933 */
1934 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1935 if (err)
1936 return err;
1937
1938 if (is_pointer_value(env, BPF_REG_0)) {
1939 verbose("R0 leaks addr as return value\n");
1940 return -EACCES;
1941 }
1942
1943 process_bpf_exit:
1944 insn_idx = pop_stack(env, &prev_insn_idx);
1945 if (insn_idx < 0) {
1946 break;
1947 } else {
1948 do_print_state = true;
1949 continue;
1950 }
1951 } else {
1952 err = check_cond_jmp_op(env, insn, &insn_idx);
1953 if (err)
1954 return err;
1955 }
1956 } else if (class == BPF_LD) {
1957 u8 mode = BPF_MODE(insn->code);
1958
1959 if (mode == BPF_ABS || mode == BPF_IND) {
1960 err = check_ld_abs(env, insn);
1961 if (err)
1962 return err;
1963
1964 } else if (mode == BPF_IMM) {
1965 err = check_ld_imm(env, insn);
1966 if (err)
1967 return err;
1968
1969 insn_idx++;
1970 } else {
1971 verbose("invalid BPF_LD mode\n");
1972 return -EINVAL;
1973 }
1974 } else {
1975 verbose("unknown insn class %d\n", class);
1976 return -EINVAL;
1977 }
1978
1979 insn_idx++;
1980 }
1981
1982 return 0;
1983 }
1984
1985 /* look for pseudo eBPF instructions that access map FDs and
1986 * replace them with actual map pointers
1987 */
1988 static int replace_map_fd_with_map_ptr(struct verifier_env *env)
1989 {
1990 struct bpf_insn *insn = env->prog->insnsi;
1991 int insn_cnt = env->prog->len;
1992 int i, j;
1993
1994 for (i = 0; i < insn_cnt; i++, insn++) {
1995 if (BPF_CLASS(insn->code) == BPF_LDX &&
1996 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
1997 verbose("BPF_LDX uses reserved fields\n");
1998 return -EINVAL;
1999 }
2000
2001 if (BPF_CLASS(insn->code) == BPF_STX &&
2002 ((BPF_MODE(insn->code) != BPF_MEM &&
2003 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2004 verbose("BPF_STX uses reserved fields\n");
2005 return -EINVAL;
2006 }
2007
2008 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2009 struct bpf_map *map;
2010 struct fd f;
2011
2012 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2013 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2014 insn[1].off != 0) {
2015 verbose("invalid bpf_ld_imm64 insn\n");
2016 return -EINVAL;
2017 }
2018
2019 if (insn->src_reg == 0)
2020 /* valid generic load 64-bit imm */
2021 goto next_insn;
2022
2023 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2024 verbose("unrecognized bpf_ld_imm64 insn\n");
2025 return -EINVAL;
2026 }
2027
2028 f = fdget(insn->imm);
2029 map = __bpf_map_get(f);
2030 if (IS_ERR(map)) {
2031 verbose("fd %d is not pointing to valid bpf_map\n",
2032 insn->imm);
2033 fdput(f);
2034 return PTR_ERR(map);
2035 }
2036
2037 /* store map pointer inside BPF_LD_IMM64 instruction */
2038 insn[0].imm = (u32) (unsigned long) map;
2039 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2040
2041 /* check whether we recorded this map already */
2042 for (j = 0; j < env->used_map_cnt; j++)
2043 if (env->used_maps[j] == map) {
2044 fdput(f);
2045 goto next_insn;
2046 }
2047
2048 if (env->used_map_cnt >= MAX_USED_MAPS) {
2049 fdput(f);
2050 return -E2BIG;
2051 }
2052
2053 /* remember this map */
2054 env->used_maps[env->used_map_cnt++] = map;
2055
2056 /* hold the map. If the program is rejected by verifier,
2057 * the map will be released by release_maps() or it
2058 * will be used by the valid program until it's unloaded
2059 * and all maps are released in free_bpf_prog_info()
2060 */
2061 bpf_map_inc(map, false);
2062 fdput(f);
2063 next_insn:
2064 insn++;
2065 i++;
2066 }
2067 }
2068
2069 /* now all pseudo BPF_LD_IMM64 instructions load valid
2070 * 'struct bpf_map *' into a register instead of user map_fd.
2071 * These pointers will be used later by verifier to validate map access.
2072 */
2073 return 0;
2074 }
2075
2076 /* drop refcnt of maps used by the rejected program */
2077 static void release_maps(struct verifier_env *env)
2078 {
2079 int i;
2080
2081 for (i = 0; i < env->used_map_cnt; i++)
2082 bpf_map_put(env->used_maps[i]);
2083 }
2084
2085 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2086 static void convert_pseudo_ld_imm64(struct verifier_env *env)
2087 {
2088 struct bpf_insn *insn = env->prog->insnsi;
2089 int insn_cnt = env->prog->len;
2090 int i;
2091
2092 for (i = 0; i < insn_cnt; i++, insn++)
2093 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2094 insn->src_reg = 0;
2095 }
2096
2097 static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
2098 {
2099 struct bpf_insn *insn = prog->insnsi;
2100 int insn_cnt = prog->len;
2101 int i;
2102
2103 for (i = 0; i < insn_cnt; i++, insn++) {
2104 if (BPF_CLASS(insn->code) != BPF_JMP ||
2105 BPF_OP(insn->code) == BPF_CALL ||
2106 BPF_OP(insn->code) == BPF_EXIT)
2107 continue;
2108
2109 /* adjust offset of jmps if necessary */
2110 if (i < pos && i + insn->off + 1 > pos)
2111 insn->off += delta;
2112 else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
2113 insn->off -= delta;
2114 }
2115 }
2116
2117 /* convert load instructions that access fields of 'struct __sk_buff'
2118 * into sequence of instructions that access fields of 'struct sk_buff'
2119 */
2120 static int convert_ctx_accesses(struct verifier_env *env)
2121 {
2122 struct bpf_insn *insn = env->prog->insnsi;
2123 int insn_cnt = env->prog->len;
2124 struct bpf_insn insn_buf[16];
2125 struct bpf_prog *new_prog;
2126 u32 cnt;
2127 int i;
2128 enum bpf_access_type type;
2129
2130 if (!env->prog->aux->ops->convert_ctx_access)
2131 return 0;
2132
2133 for (i = 0; i < insn_cnt; i++, insn++) {
2134 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2135 type = BPF_READ;
2136 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2137 type = BPF_WRITE;
2138 else
2139 continue;
2140
2141 if (insn->imm != PTR_TO_CTX) {
2142 /* clear internal mark */
2143 insn->imm = 0;
2144 continue;
2145 }
2146
2147 cnt = env->prog->aux->ops->
2148 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
2149 insn->off, insn_buf, env->prog);
2150 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2151 verbose("bpf verifier is misconfigured\n");
2152 return -EINVAL;
2153 }
2154
2155 if (cnt == 1) {
2156 memcpy(insn, insn_buf, sizeof(*insn));
2157 continue;
2158 }
2159
2160 /* several new insns need to be inserted. Make room for them */
2161 insn_cnt += cnt - 1;
2162 new_prog = bpf_prog_realloc(env->prog,
2163 bpf_prog_size(insn_cnt),
2164 GFP_USER);
2165 if (!new_prog)
2166 return -ENOMEM;
2167
2168 new_prog->len = insn_cnt;
2169
2170 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2171 sizeof(*insn) * (insn_cnt - i - cnt));
2172
2173 /* copy substitute insns in place of load instruction */
2174 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2175
2176 /* adjust branches in the whole program */
2177 adjust_branches(new_prog, i, cnt - 1);
2178
2179 /* keep walking new program and skip insns we just inserted */
2180 env->prog = new_prog;
2181 insn = new_prog->insnsi + i + cnt - 1;
2182 i += cnt - 1;
2183 }
2184
2185 return 0;
2186 }
2187
2188 static void free_states(struct verifier_env *env)
2189 {
2190 struct verifier_state_list *sl, *sln;
2191 int i;
2192
2193 if (!env->explored_states)
2194 return;
2195
2196 for (i = 0; i < env->prog->len; i++) {
2197 sl = env->explored_states[i];
2198
2199 if (sl)
2200 while (sl != STATE_LIST_MARK) {
2201 sln = sl->next;
2202 kfree(sl);
2203 sl = sln;
2204 }
2205 }
2206
2207 kfree(env->explored_states);
2208 }
2209
2210 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
2211 {
2212 char __user *log_ubuf = NULL;
2213 struct verifier_env *env;
2214 int ret = -EINVAL;
2215
2216 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
2217 return -E2BIG;
2218
2219 /* 'struct verifier_env' can be global, but since it's not small,
2220 * allocate/free it every time bpf_check() is called
2221 */
2222 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2223 if (!env)
2224 return -ENOMEM;
2225
2226 env->prog = *prog;
2227
2228 /* grab the mutex to protect few globals used by verifier */
2229 mutex_lock(&bpf_verifier_lock);
2230
2231 if (attr->log_level || attr->log_buf || attr->log_size) {
2232 /* user requested verbose verifier output
2233 * and supplied buffer to store the verification trace
2234 */
2235 log_level = attr->log_level;
2236 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2237 log_size = attr->log_size;
2238 log_len = 0;
2239
2240 ret = -EINVAL;
2241 /* log_* values have to be sane */
2242 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2243 log_level == 0 || log_ubuf == NULL)
2244 goto free_env;
2245
2246 ret = -ENOMEM;
2247 log_buf = vmalloc(log_size);
2248 if (!log_buf)
2249 goto free_env;
2250 } else {
2251 log_level = 0;
2252 }
2253
2254 ret = replace_map_fd_with_map_ptr(env);
2255 if (ret < 0)
2256 goto skip_full_check;
2257
2258 env->explored_states = kcalloc(env->prog->len,
2259 sizeof(struct verifier_state_list *),
2260 GFP_USER);
2261 ret = -ENOMEM;
2262 if (!env->explored_states)
2263 goto skip_full_check;
2264
2265 ret = check_cfg(env);
2266 if (ret < 0)
2267 goto skip_full_check;
2268
2269 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2270
2271 ret = do_check(env);
2272
2273 skip_full_check:
2274 while (pop_stack(env, NULL) >= 0);
2275 free_states(env);
2276
2277 if (ret == 0)
2278 /* program is valid, convert *(u32*)(ctx + off) accesses */
2279 ret = convert_ctx_accesses(env);
2280
2281 if (log_level && log_len >= log_size - 1) {
2282 BUG_ON(log_len >= log_size);
2283 /* verifier log exceeded user supplied buffer */
2284 ret = -ENOSPC;
2285 /* fall through to return what was recorded */
2286 }
2287
2288 /* copy verifier log back to user space including trailing zero */
2289 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2290 ret = -EFAULT;
2291 goto free_log_buf;
2292 }
2293
2294 if (ret == 0 && env->used_map_cnt) {
2295 /* if program passed verifier, update used_maps in bpf_prog_info */
2296 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2297 sizeof(env->used_maps[0]),
2298 GFP_KERNEL);
2299
2300 if (!env->prog->aux->used_maps) {
2301 ret = -ENOMEM;
2302 goto free_log_buf;
2303 }
2304
2305 memcpy(env->prog->aux->used_maps, env->used_maps,
2306 sizeof(env->used_maps[0]) * env->used_map_cnt);
2307 env->prog->aux->used_map_cnt = env->used_map_cnt;
2308
2309 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2310 * bpf_ld_imm64 instructions
2311 */
2312 convert_pseudo_ld_imm64(env);
2313 }
2314
2315 free_log_buf:
2316 if (log_level)
2317 vfree(log_buf);
2318 free_env:
2319 if (!env->prog->aux->used_maps)
2320 /* if we didn't copy map pointers into bpf_prog_info, release
2321 * them now. Otherwise free_bpf_prog_info() will release them.
2322 */
2323 release_maps(env);
2324 *prog = env->prog;
2325 kfree(env);
2326 mutex_unlock(&bpf_verifier_lock);
2327 return ret;
2328 }
Linux kernel - Deliverables
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