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RDMA/nes: don't leak skb if carrier down
[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 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1378 verbose("BPF_LD_ABS uses reserved fields\n");
1379 return -EINVAL;
1380 }
1381
1382 /* check whether implicit source operand (register R6) is readable */
1383 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1384 if (err)
1385 return err;
1386
1387 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1388 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1389 return -EINVAL;
1390 }
1391
1392 if (mode == BPF_IND) {
1393 /* check explicit source operand */
1394 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1395 if (err)
1396 return err;
1397 }
1398
1399 /* reset caller saved regs to unreadable */
1400 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1401 reg = regs + caller_saved[i];
1402 reg->type = NOT_INIT;
1403 reg->imm = 0;
1404 }
1405
1406 /* mark destination R0 register as readable, since it contains
1407 * the value fetched from the packet
1408 */
1409 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1410 return 0;
1411 }
1412
1413 /* non-recursive DFS pseudo code
1414 * 1 procedure DFS-iterative(G,v):
1415 * 2 label v as discovered
1416 * 3 let S be a stack
1417 * 4 S.push(v)
1418 * 5 while S is not empty
1419 * 6 t <- S.pop()
1420 * 7 if t is what we're looking for:
1421 * 8 return t
1422 * 9 for all edges e in G.adjacentEdges(t) do
1423 * 10 if edge e is already labelled
1424 * 11 continue with the next edge
1425 * 12 w <- G.adjacentVertex(t,e)
1426 * 13 if vertex w is not discovered and not explored
1427 * 14 label e as tree-edge
1428 * 15 label w as discovered
1429 * 16 S.push(w)
1430 * 17 continue at 5
1431 * 18 else if vertex w is discovered
1432 * 19 label e as back-edge
1433 * 20 else
1434 * 21 // vertex w is explored
1435 * 22 label e as forward- or cross-edge
1436 * 23 label t as explored
1437 * 24 S.pop()
1438 *
1439 * convention:
1440 * 0x10 - discovered
1441 * 0x11 - discovered and fall-through edge labelled
1442 * 0x12 - discovered and fall-through and branch edges labelled
1443 * 0x20 - explored
1444 */
1445
1446 enum {
1447 DISCOVERED = 0x10,
1448 EXPLORED = 0x20,
1449 FALLTHROUGH = 1,
1450 BRANCH = 2,
1451 };
1452
1453 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1454
1455 static int *insn_stack; /* stack of insns to process */
1456 static int cur_stack; /* current stack index */
1457 static int *insn_state;
1458
1459 /* t, w, e - match pseudo-code above:
1460 * t - index of current instruction
1461 * w - next instruction
1462 * e - edge
1463 */
1464 static int push_insn(int t, int w, int e, struct verifier_env *env)
1465 {
1466 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1467 return 0;
1468
1469 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1470 return 0;
1471
1472 if (w < 0 || w >= env->prog->len) {
1473 verbose("jump out of range from insn %d to %d\n", t, w);
1474 return -EINVAL;
1475 }
1476
1477 if (e == BRANCH)
1478 /* mark branch target for state pruning */
1479 env->explored_states[w] = STATE_LIST_MARK;
1480
1481 if (insn_state[w] == 0) {
1482 /* tree-edge */
1483 insn_state[t] = DISCOVERED | e;
1484 insn_state[w] = DISCOVERED;
1485 if (cur_stack >= env->prog->len)
1486 return -E2BIG;
1487 insn_stack[cur_stack++] = w;
1488 return 1;
1489 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1490 verbose("back-edge from insn %d to %d\n", t, w);
1491 return -EINVAL;
1492 } else if (insn_state[w] == EXPLORED) {
1493 /* forward- or cross-edge */
1494 insn_state[t] = DISCOVERED | e;
1495 } else {
1496 verbose("insn state internal bug\n");
1497 return -EFAULT;
1498 }
1499 return 0;
1500 }
1501
1502 /* non-recursive depth-first-search to detect loops in BPF program
1503 * loop == back-edge in directed graph
1504 */
1505 static int check_cfg(struct verifier_env *env)
1506 {
1507 struct bpf_insn *insns = env->prog->insnsi;
1508 int insn_cnt = env->prog->len;
1509 int ret = 0;
1510 int i, t;
1511
1512 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1513 if (!insn_state)
1514 return -ENOMEM;
1515
1516 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1517 if (!insn_stack) {
1518 kfree(insn_state);
1519 return -ENOMEM;
1520 }
1521
1522 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1523 insn_stack[0] = 0; /* 0 is the first instruction */
1524 cur_stack = 1;
1525
1526 peek_stack:
1527 if (cur_stack == 0)
1528 goto check_state;
1529 t = insn_stack[cur_stack - 1];
1530
1531 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1532 u8 opcode = BPF_OP(insns[t].code);
1533
1534 if (opcode == BPF_EXIT) {
1535 goto mark_explored;
1536 } else if (opcode == BPF_CALL) {
1537 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1538 if (ret == 1)
1539 goto peek_stack;
1540 else if (ret < 0)
1541 goto err_free;
1542 } else if (opcode == BPF_JA) {
1543 if (BPF_SRC(insns[t].code) != BPF_K) {
1544 ret = -EINVAL;
1545 goto err_free;
1546 }
1547 /* unconditional jump with single edge */
1548 ret = push_insn(t, t + insns[t].off + 1,
1549 FALLTHROUGH, env);
1550 if (ret == 1)
1551 goto peek_stack;
1552 else if (ret < 0)
1553 goto err_free;
1554 /* tell verifier to check for equivalent states
1555 * after every call and jump
1556 */
1557 if (t + 1 < insn_cnt)
1558 env->explored_states[t + 1] = STATE_LIST_MARK;
1559 } else {
1560 /* conditional jump with two edges */
1561 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1562 if (ret == 1)
1563 goto peek_stack;
1564 else if (ret < 0)
1565 goto err_free;
1566
1567 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1568 if (ret == 1)
1569 goto peek_stack;
1570 else if (ret < 0)
1571 goto err_free;
1572 }
1573 } else {
1574 /* all other non-branch instructions with single
1575 * fall-through edge
1576 */
1577 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1578 if (ret == 1)
1579 goto peek_stack;
1580 else if (ret < 0)
1581 goto err_free;
1582 }
1583
1584 mark_explored:
1585 insn_state[t] = EXPLORED;
1586 if (cur_stack-- <= 0) {
1587 verbose("pop stack internal bug\n");
1588 ret = -EFAULT;
1589 goto err_free;
1590 }
1591 goto peek_stack;
1592
1593 check_state:
1594 for (i = 0; i < insn_cnt; i++) {
1595 if (insn_state[i] != EXPLORED) {
1596 verbose("unreachable insn %d\n", i);
1597 ret = -EINVAL;
1598 goto err_free;
1599 }
1600 }
1601 ret = 0; /* cfg looks good */
1602
1603 err_free:
1604 kfree(insn_state);
1605 kfree(insn_stack);
1606 return ret;
1607 }
1608
1609 /* compare two verifier states
1610 *
1611 * all states stored in state_list are known to be valid, since
1612 * verifier reached 'bpf_exit' instruction through them
1613 *
1614 * this function is called when verifier exploring different branches of
1615 * execution popped from the state stack. If it sees an old state that has
1616 * more strict register state and more strict stack state then this execution
1617 * branch doesn't need to be explored further, since verifier already
1618 * concluded that more strict state leads to valid finish.
1619 *
1620 * Therefore two states are equivalent if register state is more conservative
1621 * and explored stack state is more conservative than the current one.
1622 * Example:
1623 * explored current
1624 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1625 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1626 *
1627 * In other words if current stack state (one being explored) has more
1628 * valid slots than old one that already passed validation, it means
1629 * the verifier can stop exploring and conclude that current state is valid too
1630 *
1631 * Similarly with registers. If explored state has register type as invalid
1632 * whereas register type in current state is meaningful, it means that
1633 * the current state will reach 'bpf_exit' instruction safely
1634 */
1635 static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1636 {
1637 int i;
1638
1639 for (i = 0; i < MAX_BPF_REG; i++) {
1640 if (memcmp(&old->regs[i], &cur->regs[i],
1641 sizeof(old->regs[0])) != 0) {
1642 if (old->regs[i].type == NOT_INIT ||
1643 (old->regs[i].type == UNKNOWN_VALUE &&
1644 cur->regs[i].type != NOT_INIT))
1645 continue;
1646 return false;
1647 }
1648 }
1649
1650 for (i = 0; i < MAX_BPF_STACK; i++) {
1651 if (old->stack_slot_type[i] == STACK_INVALID)
1652 continue;
1653 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1654 /* Ex: old explored (safe) state has STACK_SPILL in
1655 * this stack slot, but current has has STACK_MISC ->
1656 * this verifier states are not equivalent,
1657 * return false to continue verification of this path
1658 */
1659 return false;
1660 if (i % BPF_REG_SIZE)
1661 continue;
1662 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1663 &cur->spilled_regs[i / BPF_REG_SIZE],
1664 sizeof(old->spilled_regs[0])))
1665 /* when explored and current stack slot types are
1666 * the same, check that stored pointers types
1667 * are the same as well.
1668 * Ex: explored safe path could have stored
1669 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1670 * but current path has stored:
1671 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1672 * such verifier states are not equivalent.
1673 * return false to continue verification of this path
1674 */
1675 return false;
1676 else
1677 continue;
1678 }
1679 return true;
1680 }
1681
1682 static int is_state_visited(struct verifier_env *env, int insn_idx)
1683 {
1684 struct verifier_state_list *new_sl;
1685 struct verifier_state_list *sl;
1686
1687 sl = env->explored_states[insn_idx];
1688 if (!sl)
1689 /* this 'insn_idx' instruction wasn't marked, so we will not
1690 * be doing state search here
1691 */
1692 return 0;
1693
1694 while (sl != STATE_LIST_MARK) {
1695 if (states_equal(&sl->state, &env->cur_state))
1696 /* reached equivalent register/stack state,
1697 * prune the search
1698 */
1699 return 1;
1700 sl = sl->next;
1701 }
1702
1703 /* there were no equivalent states, remember current one.
1704 * technically the current state is not proven to be safe yet,
1705 * but it will either reach bpf_exit (which means it's safe) or
1706 * it will be rejected. Since there are no loops, we won't be
1707 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1708 */
1709 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1710 if (!new_sl)
1711 return -ENOMEM;
1712
1713 /* add new state to the head of linked list */
1714 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1715 new_sl->next = env->explored_states[insn_idx];
1716 env->explored_states[insn_idx] = new_sl;
1717 return 0;
1718 }
1719
1720 static int do_check(struct verifier_env *env)
1721 {
1722 struct verifier_state *state = &env->cur_state;
1723 struct bpf_insn *insns = env->prog->insnsi;
1724 struct reg_state *regs = state->regs;
1725 int insn_cnt = env->prog->len;
1726 int insn_idx, prev_insn_idx = 0;
1727 int insn_processed = 0;
1728 bool do_print_state = false;
1729
1730 init_reg_state(regs);
1731 insn_idx = 0;
1732 for (;;) {
1733 struct bpf_insn *insn;
1734 u8 class;
1735 int err;
1736
1737 if (insn_idx >= insn_cnt) {
1738 verbose("invalid insn idx %d insn_cnt %d\n",
1739 insn_idx, insn_cnt);
1740 return -EFAULT;
1741 }
1742
1743 insn = &insns[insn_idx];
1744 class = BPF_CLASS(insn->code);
1745
1746 if (++insn_processed > 32768) {
1747 verbose("BPF program is too large. Proccessed %d insn\n",
1748 insn_processed);
1749 return -E2BIG;
1750 }
1751
1752 err = is_state_visited(env, insn_idx);
1753 if (err < 0)
1754 return err;
1755 if (err == 1) {
1756 /* found equivalent state, can prune the search */
1757 if (log_level) {
1758 if (do_print_state)
1759 verbose("\nfrom %d to %d: safe\n",
1760 prev_insn_idx, insn_idx);
1761 else
1762 verbose("%d: safe\n", insn_idx);
1763 }
1764 goto process_bpf_exit;
1765 }
1766
1767 if (log_level && do_print_state) {
1768 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1769 print_verifier_state(env);
1770 do_print_state = false;
1771 }
1772
1773 if (log_level) {
1774 verbose("%d: ", insn_idx);
1775 print_bpf_insn(insn);
1776 }
1777
1778 if (class == BPF_ALU || class == BPF_ALU64) {
1779 err = check_alu_op(env, insn);
1780 if (err)
1781 return err;
1782
1783 } else if (class == BPF_LDX) {
1784 enum bpf_reg_type src_reg_type;
1785
1786 /* check for reserved fields is already done */
1787
1788 /* check src operand */
1789 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1790 if (err)
1791 return err;
1792
1793 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1794 if (err)
1795 return err;
1796
1797 src_reg_type = regs[insn->src_reg].type;
1798
1799 /* check that memory (src_reg + off) is readable,
1800 * the state of dst_reg will be updated by this func
1801 */
1802 err = check_mem_access(env, insn->src_reg, insn->off,
1803 BPF_SIZE(insn->code), BPF_READ,
1804 insn->dst_reg);
1805 if (err)
1806 return err;
1807
1808 if (BPF_SIZE(insn->code) != BPF_W) {
1809 insn_idx++;
1810 continue;
1811 }
1812
1813 if (insn->imm == 0) {
1814 /* saw a valid insn
1815 * dst_reg = *(u32 *)(src_reg + off)
1816 * use reserved 'imm' field to mark this insn
1817 */
1818 insn->imm = src_reg_type;
1819
1820 } else if (src_reg_type != insn->imm &&
1821 (src_reg_type == PTR_TO_CTX ||
1822 insn->imm == PTR_TO_CTX)) {
1823 /* ABuser program is trying to use the same insn
1824 * dst_reg = *(u32*) (src_reg + off)
1825 * with different pointer types:
1826 * src_reg == ctx in one branch and
1827 * src_reg == stack|map in some other branch.
1828 * Reject it.
1829 */
1830 verbose("same insn cannot be used with different pointers\n");
1831 return -EINVAL;
1832 }
1833
1834 } else if (class == BPF_STX) {
1835 enum bpf_reg_type dst_reg_type;
1836
1837 if (BPF_MODE(insn->code) == BPF_XADD) {
1838 err = check_xadd(env, insn);
1839 if (err)
1840 return err;
1841 insn_idx++;
1842 continue;
1843 }
1844
1845 /* check src1 operand */
1846 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1847 if (err)
1848 return err;
1849 /* check src2 operand */
1850 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1851 if (err)
1852 return err;
1853
1854 dst_reg_type = regs[insn->dst_reg].type;
1855
1856 /* check that memory (dst_reg + off) is writeable */
1857 err = check_mem_access(env, insn->dst_reg, insn->off,
1858 BPF_SIZE(insn->code), BPF_WRITE,
1859 insn->src_reg);
1860 if (err)
1861 return err;
1862
1863 if (insn->imm == 0) {
1864 insn->imm = dst_reg_type;
1865 } else if (dst_reg_type != insn->imm &&
1866 (dst_reg_type == PTR_TO_CTX ||
1867 insn->imm == PTR_TO_CTX)) {
1868 verbose("same insn cannot be used with different pointers\n");
1869 return -EINVAL;
1870 }
1871
1872 } else if (class == BPF_ST) {
1873 if (BPF_MODE(insn->code) != BPF_MEM ||
1874 insn->src_reg != BPF_REG_0) {
1875 verbose("BPF_ST uses reserved fields\n");
1876 return -EINVAL;
1877 }
1878 /* check src operand */
1879 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1880 if (err)
1881 return err;
1882
1883 /* check that memory (dst_reg + off) is writeable */
1884 err = check_mem_access(env, insn->dst_reg, insn->off,
1885 BPF_SIZE(insn->code), BPF_WRITE,
1886 -1);
1887 if (err)
1888 return err;
1889
1890 } else if (class == BPF_JMP) {
1891 u8 opcode = BPF_OP(insn->code);
1892
1893 if (opcode == BPF_CALL) {
1894 if (BPF_SRC(insn->code) != BPF_K ||
1895 insn->off != 0 ||
1896 insn->src_reg != BPF_REG_0 ||
1897 insn->dst_reg != BPF_REG_0) {
1898 verbose("BPF_CALL uses reserved fields\n");
1899 return -EINVAL;
1900 }
1901
1902 err = check_call(env, insn->imm);
1903 if (err)
1904 return err;
1905
1906 } else if (opcode == BPF_JA) {
1907 if (BPF_SRC(insn->code) != BPF_K ||
1908 insn->imm != 0 ||
1909 insn->src_reg != BPF_REG_0 ||
1910 insn->dst_reg != BPF_REG_0) {
1911 verbose("BPF_JA uses reserved fields\n");
1912 return -EINVAL;
1913 }
1914
1915 insn_idx += insn->off + 1;
1916 continue;
1917
1918 } else if (opcode == BPF_EXIT) {
1919 if (BPF_SRC(insn->code) != BPF_K ||
1920 insn->imm != 0 ||
1921 insn->src_reg != BPF_REG_0 ||
1922 insn->dst_reg != BPF_REG_0) {
1923 verbose("BPF_EXIT uses reserved fields\n");
1924 return -EINVAL;
1925 }
1926
1927 /* eBPF calling convetion is such that R0 is used
1928 * to return the value from eBPF program.
1929 * Make sure that it's readable at this time
1930 * of bpf_exit, which means that program wrote
1931 * something into it earlier
1932 */
1933 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1934 if (err)
1935 return err;
1936
1937 if (is_pointer_value(env, BPF_REG_0)) {
1938 verbose("R0 leaks addr as return value\n");
1939 return -EACCES;
1940 }
1941
1942 process_bpf_exit:
1943 insn_idx = pop_stack(env, &prev_insn_idx);
1944 if (insn_idx < 0) {
1945 break;
1946 } else {
1947 do_print_state = true;
1948 continue;
1949 }
1950 } else {
1951 err = check_cond_jmp_op(env, insn, &insn_idx);
1952 if (err)
1953 return err;
1954 }
1955 } else if (class == BPF_LD) {
1956 u8 mode = BPF_MODE(insn->code);
1957
1958 if (mode == BPF_ABS || mode == BPF_IND) {
1959 err = check_ld_abs(env, insn);
1960 if (err)
1961 return err;
1962
1963 } else if (mode == BPF_IMM) {
1964 err = check_ld_imm(env, insn);
1965 if (err)
1966 return err;
1967
1968 insn_idx++;
1969 } else {
1970 verbose("invalid BPF_LD mode\n");
1971 return -EINVAL;
1972 }
1973 } else {
1974 verbose("unknown insn class %d\n", class);
1975 return -EINVAL;
1976 }
1977
1978 insn_idx++;
1979 }
1980
1981 return 0;
1982 }
1983
1984 /* look for pseudo eBPF instructions that access map FDs and
1985 * replace them with actual map pointers
1986 */
1987 static int replace_map_fd_with_map_ptr(struct verifier_env *env)
1988 {
1989 struct bpf_insn *insn = env->prog->insnsi;
1990 int insn_cnt = env->prog->len;
1991 int i, j;
1992
1993 for (i = 0; i < insn_cnt; i++, insn++) {
1994 if (BPF_CLASS(insn->code) == BPF_LDX &&
1995 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
1996 verbose("BPF_LDX uses reserved fields\n");
1997 return -EINVAL;
1998 }
1999
2000 if (BPF_CLASS(insn->code) == BPF_STX &&
2001 ((BPF_MODE(insn->code) != BPF_MEM &&
2002 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2003 verbose("BPF_STX uses reserved fields\n");
2004 return -EINVAL;
2005 }
2006
2007 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2008 struct bpf_map *map;
2009 struct fd f;
2010
2011 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2012 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2013 insn[1].off != 0) {
2014 verbose("invalid bpf_ld_imm64 insn\n");
2015 return -EINVAL;
2016 }
2017
2018 if (insn->src_reg == 0)
2019 /* valid generic load 64-bit imm */
2020 goto next_insn;
2021
2022 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2023 verbose("unrecognized bpf_ld_imm64 insn\n");
2024 return -EINVAL;
2025 }
2026
2027 f = fdget(insn->imm);
2028 map = __bpf_map_get(f);
2029 if (IS_ERR(map)) {
2030 verbose("fd %d is not pointing to valid bpf_map\n",
2031 insn->imm);
2032 fdput(f);
2033 return PTR_ERR(map);
2034 }
2035
2036 /* store map pointer inside BPF_LD_IMM64 instruction */
2037 insn[0].imm = (u32) (unsigned long) map;
2038 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2039
2040 /* check whether we recorded this map already */
2041 for (j = 0; j < env->used_map_cnt; j++)
2042 if (env->used_maps[j] == map) {
2043 fdput(f);
2044 goto next_insn;
2045 }
2046
2047 if (env->used_map_cnt >= MAX_USED_MAPS) {
2048 fdput(f);
2049 return -E2BIG;
2050 }
2051
2052 /* remember this map */
2053 env->used_maps[env->used_map_cnt++] = map;
2054
2055 /* hold the map. If the program is rejected by verifier,
2056 * the map will be released by release_maps() or it
2057 * will be used by the valid program until it's unloaded
2058 * and all maps are released in free_bpf_prog_info()
2059 */
2060 bpf_map_inc(map, false);
2061 fdput(f);
2062 next_insn:
2063 insn++;
2064 i++;
2065 }
2066 }
2067
2068 /* now all pseudo BPF_LD_IMM64 instructions load valid
2069 * 'struct bpf_map *' into a register instead of user map_fd.
2070 * These pointers will be used later by verifier to validate map access.
2071 */
2072 return 0;
2073 }
2074
2075 /* drop refcnt of maps used by the rejected program */
2076 static void release_maps(struct verifier_env *env)
2077 {
2078 int i;
2079
2080 for (i = 0; i < env->used_map_cnt; i++)
2081 bpf_map_put(env->used_maps[i]);
2082 }
2083
2084 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2085 static void convert_pseudo_ld_imm64(struct verifier_env *env)
2086 {
2087 struct bpf_insn *insn = env->prog->insnsi;
2088 int insn_cnt = env->prog->len;
2089 int i;
2090
2091 for (i = 0; i < insn_cnt; i++, insn++)
2092 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2093 insn->src_reg = 0;
2094 }
2095
2096 static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
2097 {
2098 struct bpf_insn *insn = prog->insnsi;
2099 int insn_cnt = prog->len;
2100 int i;
2101
2102 for (i = 0; i < insn_cnt; i++, insn++) {
2103 if (BPF_CLASS(insn->code) != BPF_JMP ||
2104 BPF_OP(insn->code) == BPF_CALL ||
2105 BPF_OP(insn->code) == BPF_EXIT)
2106 continue;
2107
2108 /* adjust offset of jmps if necessary */
2109 if (i < pos && i + insn->off + 1 > pos)
2110 insn->off += delta;
2111 else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
2112 insn->off -= delta;
2113 }
2114 }
2115
2116 /* convert load instructions that access fields of 'struct __sk_buff'
2117 * into sequence of instructions that access fields of 'struct sk_buff'
2118 */
2119 static int convert_ctx_accesses(struct verifier_env *env)
2120 {
2121 struct bpf_insn *insn = env->prog->insnsi;
2122 int insn_cnt = env->prog->len;
2123 struct bpf_insn insn_buf[16];
2124 struct bpf_prog *new_prog;
2125 u32 cnt;
2126 int i;
2127 enum bpf_access_type type;
2128
2129 if (!env->prog->aux->ops->convert_ctx_access)
2130 return 0;
2131
2132 for (i = 0; i < insn_cnt; i++, insn++) {
2133 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2134 type = BPF_READ;
2135 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2136 type = BPF_WRITE;
2137 else
2138 continue;
2139
2140 if (insn->imm != PTR_TO_CTX) {
2141 /* clear internal mark */
2142 insn->imm = 0;
2143 continue;
2144 }
2145
2146 cnt = env->prog->aux->ops->
2147 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
2148 insn->off, insn_buf, env->prog);
2149 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2150 verbose("bpf verifier is misconfigured\n");
2151 return -EINVAL;
2152 }
2153
2154 if (cnt == 1) {
2155 memcpy(insn, insn_buf, sizeof(*insn));
2156 continue;
2157 }
2158
2159 /* several new insns need to be inserted. Make room for them */
2160 insn_cnt += cnt - 1;
2161 new_prog = bpf_prog_realloc(env->prog,
2162 bpf_prog_size(insn_cnt),
2163 GFP_USER);
2164 if (!new_prog)
2165 return -ENOMEM;
2166
2167 new_prog->len = insn_cnt;
2168
2169 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2170 sizeof(*insn) * (insn_cnt - i - cnt));
2171
2172 /* copy substitute insns in place of load instruction */
2173 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2174
2175 /* adjust branches in the whole program */
2176 adjust_branches(new_prog, i, cnt - 1);
2177
2178 /* keep walking new program and skip insns we just inserted */
2179 env->prog = new_prog;
2180 insn = new_prog->insnsi + i + cnt - 1;
2181 i += cnt - 1;
2182 }
2183
2184 return 0;
2185 }
2186
2187 static void free_states(struct verifier_env *env)
2188 {
2189 struct verifier_state_list *sl, *sln;
2190 int i;
2191
2192 if (!env->explored_states)
2193 return;
2194
2195 for (i = 0; i < env->prog->len; i++) {
2196 sl = env->explored_states[i];
2197
2198 if (sl)
2199 while (sl != STATE_LIST_MARK) {
2200 sln = sl->next;
2201 kfree(sl);
2202 sl = sln;
2203 }
2204 }
2205
2206 kfree(env->explored_states);
2207 }
2208
2209 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
2210 {
2211 char __user *log_ubuf = NULL;
2212 struct verifier_env *env;
2213 int ret = -EINVAL;
2214
2215 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
2216 return -E2BIG;
2217
2218 /* 'struct verifier_env' can be global, but since it's not small,
2219 * allocate/free it every time bpf_check() is called
2220 */
2221 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2222 if (!env)
2223 return -ENOMEM;
2224
2225 env->prog = *prog;
2226
2227 /* grab the mutex to protect few globals used by verifier */
2228 mutex_lock(&bpf_verifier_lock);
2229
2230 if (attr->log_level || attr->log_buf || attr->log_size) {
2231 /* user requested verbose verifier output
2232 * and supplied buffer to store the verification trace
2233 */
2234 log_level = attr->log_level;
2235 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2236 log_size = attr->log_size;
2237 log_len = 0;
2238
2239 ret = -EINVAL;
2240 /* log_* values have to be sane */
2241 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2242 log_level == 0 || log_ubuf == NULL)
2243 goto free_env;
2244
2245 ret = -ENOMEM;
2246 log_buf = vmalloc(log_size);
2247 if (!log_buf)
2248 goto free_env;
2249 } else {
2250 log_level = 0;
2251 }
2252
2253 ret = replace_map_fd_with_map_ptr(env);
2254 if (ret < 0)
2255 goto skip_full_check;
2256
2257 env->explored_states = kcalloc(env->prog->len,
2258 sizeof(struct verifier_state_list *),
2259 GFP_USER);
2260 ret = -ENOMEM;
2261 if (!env->explored_states)
2262 goto skip_full_check;
2263
2264 ret = check_cfg(env);
2265 if (ret < 0)
2266 goto skip_full_check;
2267
2268 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2269
2270 ret = do_check(env);
2271
2272 skip_full_check:
2273 while (pop_stack(env, NULL) >= 0);
2274 free_states(env);
2275
2276 if (ret == 0)
2277 /* program is valid, convert *(u32*)(ctx + off) accesses */
2278 ret = convert_ctx_accesses(env);
2279
2280 if (log_level && log_len >= log_size - 1) {
2281 BUG_ON(log_len >= log_size);
2282 /* verifier log exceeded user supplied buffer */
2283 ret = -ENOSPC;
2284 /* fall through to return what was recorded */
2285 }
2286
2287 /* copy verifier log back to user space including trailing zero */
2288 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2289 ret = -EFAULT;
2290 goto free_log_buf;
2291 }
2292
2293 if (ret == 0 && env->used_map_cnt) {
2294 /* if program passed verifier, update used_maps in bpf_prog_info */
2295 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2296 sizeof(env->used_maps[0]),
2297 GFP_KERNEL);
2298
2299 if (!env->prog->aux->used_maps) {
2300 ret = -ENOMEM;
2301 goto free_log_buf;
2302 }
2303
2304 memcpy(env->prog->aux->used_maps, env->used_maps,
2305 sizeof(env->used_maps[0]) * env->used_map_cnt);
2306 env->prog->aux->used_map_cnt = env->used_map_cnt;
2307
2308 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2309 * bpf_ld_imm64 instructions
2310 */
2311 convert_pseudo_ld_imm64(env);
2312 }
2313
2314 free_log_buf:
2315 if (log_level)
2316 vfree(log_buf);
2317 free_env:
2318 if (!env->prog->aux->used_maps)
2319 /* if we didn't copy map pointers into bpf_prog_info, release
2320 * them now. Otherwise free_bpf_prog_info() will release them.
2321 */
2322 release_maps(env);
2323 *prog = env->prog;
2324 kfree(env);
2325 mutex_unlock(&bpf_verifier_lock);
2326 return ret;
2327 }
Linux kernel - Deliverables
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