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Merge branch 'mlx5e-next'
[linux-2.6-block.git] / kernel / bpf / verifier.c
CommitLineData
51580e79
AS		 1/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * This program is distributed in the hope that it will be useful, but
8 * WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
10 * General Public License for more details.
11 */
12#include <linux/kernel.h>
13#include <linux/types.h>
14#include <linux/slab.h>
15#include <linux/bpf.h>
16#include <linux/filter.h>
17#include <net/netlink.h>
18#include <linux/file.h>
19#include <linux/vmalloc.h>
20
21/* bpf_check() is a static code analyzer that walks eBPF program
22 * instruction by instruction and updates register/stack state.
23 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
24 *
25 * The first pass is depth-first-search to check that the program is a DAG.
26 * It rejects the following programs:
27 * - larger than BPF_MAXINSNS insns
28 * - if loop is present (detected via back-edge)
29 * - unreachable insns exist (shouldn't be a forest. program = one function)
30 * - out of bounds or malformed jumps
31 * The second pass is all possible path descent from the 1st insn.
32 * Since it's analyzing all pathes through the program, the length of the
33 * analysis is limited to 32k insn, which may be hit even if total number of
34 * insn is less then 4K, but there are too many branches that change stack/regs.
35 * Number of 'branches to be analyzed' is limited to 1k
36 *
37 * On entry to each instruction, each register has a type, and the instruction
38 * changes the types of the registers depending on instruction semantics.
39 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
40 * copied to R1.
41 *
42 * All registers are 64-bit.
43 * R0 - return register
44 * R1-R5 argument passing registers
45 * R6-R9 callee saved registers
46 * R10 - frame pointer read-only
47 *
48 * At the start of BPF program the register R1 contains a pointer to bpf_context
49 * and has type PTR_TO_CTX.
50 *
51 * Verifier tracks arithmetic operations on pointers in case:
52 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
53 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
54 * 1st insn copies R10 (which has FRAME_PTR) type into R1
55 * and 2nd arithmetic instruction is pattern matched to recognize
56 * that it wants to construct a pointer to some element within stack.
57 * So after 2nd insn, the register R1 has type PTR_TO_STACK
58 * (and -20 constant is saved for further stack bounds checking).
59 * Meaning that this reg is a pointer to stack plus known immediate constant.
60 *
61 * Most of the time the registers have UNKNOWN_VALUE type, which
62 * means the register has some value, but it's not a valid pointer.
63 * (like pointer plus pointer becomes UNKNOWN_VALUE type)
64 *
65 * When verifier sees load or store instructions the type of base register
66 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
67 * types recognized by check_mem_access() function.
68 *
69 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
70 * and the range of [ptr, ptr + map's value_size) is accessible.
71 *
72 * registers used to pass values to function calls are checked against
73 * function argument constraints.
74 *
75 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
76 * It means that the register type passed to this function must be
77 * PTR_TO_STACK and it will be used inside the function as
78 * 'pointer to map element key'
79 *
80 * For example the argument constraints for bpf_map_lookup_elem():
81 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
82 * .arg1_type = ARG_CONST_MAP_PTR,
83 * .arg2_type = ARG_PTR_TO_MAP_KEY,
84 *
85 * ret_type says that this function returns 'pointer to map elem value or null'
86 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
87 * 2nd argument should be a pointer to stack, which will be used inside
88 * the helper function as a pointer to map element key.
89 *
90 * On the kernel side the helper function looks like:
91 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
92 * {
93 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
94 * void *key = (void *) (unsigned long) r2;
95 * void *value;
96 *
97 * here kernel can access 'key' and 'map' pointers safely, knowing that
98 * [key, key + map->key_size) bytes are valid and were initialized on
99 * the stack of eBPF program.
100 * }
101 *
102 * Corresponding eBPF program may look like:
103 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
104 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
105 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
106 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
107 * here verifier looks at prototype of map_lookup_elem() and sees:
108 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
109 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
110 *
111 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
112 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
113 * and were initialized prior to this call.
114 * If it's ok, then verifier allows this BPF_CALL insn and looks at
115 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
116 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
117 * returns ether pointer to map value or NULL.
118 *
119 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
120 * insn, the register holding that pointer in the true branch changes state to
121 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
122 * branch. See check_cond_jmp_op().
123 *
124 * After the call R0 is set to return type of the function and registers R1-R5
125 * are set to NOT_INIT to indicate that they are no longer readable.
126 */
127
17a52670
AS		 128/* types of values stored in eBPF registers */
129enum bpf_reg_type {
130 NOT_INIT = 0, /* nothing was written into register */
131 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */
132 PTR_TO_CTX, /* reg points to bpf_context */
133 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */
134 PTR_TO_MAP_VALUE, /* reg points to map element value */
135 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
136 FRAME_PTR, /* reg == frame_pointer */
137 PTR_TO_STACK, /* reg == frame_pointer + imm */
138 CONST_IMM, /* constant integer value */
139};
140
141struct reg_state {
142 enum bpf_reg_type type;
143 union {
144 /* valid when type == CONST_IMM | PTR_TO_STACK */
145 int imm;
146
147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
148 * PTR_TO_MAP_VALUE_OR_NULL
149 */
150 struct bpf_map *map_ptr;
151 };
152};
153
154enum bpf_stack_slot_type {
155 STACK_INVALID, /* nothing was stored in this stack slot */
9c399760 156 STACK_SPILL, /* register spilled into stack */
17a52670
AS		 157 STACK_MISC /* BPF program wrote some data into this slot */
158};
159
9c399760 160#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
17a52670
AS		 161
162/* state of the program:
163 * type of all registers and stack info
164 */
165struct verifier_state {
166 struct reg_state regs[MAX_BPF_REG];
9c399760
AS		 167 u8 stack_slot_type[MAX_BPF_STACK];
168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
17a52670
AS		 169};
170
171/* linked list of verifier states used to prune search */
172struct 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 */
178struct 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
0246e64d
AS		 189#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
190
cbd35700
AS		 191/* single container for all structs
192 * one verifier_env per bpf_check() call
193 */
194struct verifier_env {
0246e64d 195 struct bpf_prog *prog; /* eBPF program being verified */
17a52670
AS		 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 */
f1bca824 199 struct verifier_state_list **explored_states; /* search pruning optimization */
0246e64d
AS		 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 */
cbd35700
AS		 202};
203
204/* verbose verifier prints what it's seeing
205 * bpf_check() is called under lock, so no race to access these global vars
206 */
207static u32 log_level, log_size, log_len;
208static char *log_buf;
209
210static DEFINE_MUTEX(bpf_verifier_lock);
211
212/* log_level controls verbosity level of eBPF verifier.
213 * verbose() is used to dump the verification trace to the log, so the user
214 * can figure out what's wrong with the program
215 */
216static void verbose(const char *fmt, ...)
217{
218 va_list args;
219
220 if (log_level == 0 || log_len >= log_size - 1)
221 return;
222
223 va_start(args, fmt);
224 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
225 va_end(args);
226}
227
17a52670
AS		 228/* string representation of 'enum bpf_reg_type' */
229static const char * const reg_type_str[] = {
230 [NOT_INIT] = "?",
231 [UNKNOWN_VALUE] = "inv",
232 [PTR_TO_CTX] = "ctx",
233 [CONST_PTR_TO_MAP] = "map_ptr",
234 [PTR_TO_MAP_VALUE] = "map_value",
235 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
236 [FRAME_PTR] = "fp",
237 [PTR_TO_STACK] = "fp",
238 [CONST_IMM] = "imm",
239};
240
241static void print_verifier_state(struct verifier_env *env)
242{
243 enum bpf_reg_type t;
244 int i;
245
246 for (i = 0; i < MAX_BPF_REG; i++) {
247 t = env->cur_state.regs[i].type;
248 if (t == NOT_INIT)
249 continue;
250 verbose(" R%d=%s", i, reg_type_str[t]);
251 if (t == CONST_IMM || t == PTR_TO_STACK)
252 verbose("%d", env->cur_state.regs[i].imm);
253 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
254 t == PTR_TO_MAP_VALUE_OR_NULL)
255 verbose("(ks=%d,vs=%d)",
256 env->cur_state.regs[i].map_ptr->key_size,
257 env->cur_state.regs[i].map_ptr->value_size);
258 }
9c399760
AS		 259 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
260 if (env->cur_state.stack_slot_type[i] == STACK_SPILL)
17a52670 261 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
9c399760 262 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]);
17a52670
AS		 263 }
264 verbose("\n");
265}
266
cbd35700
AS		 267static const char *const bpf_class_string[] = {
268 [BPF_LD] = "ld",
269 [BPF_LDX] = "ldx",
270 [BPF_ST] = "st",
271 [BPF_STX] = "stx",
272 [BPF_ALU] = "alu",
273 [BPF_JMP] = "jmp",
274 [BPF_RET] = "BUG",
275 [BPF_ALU64] = "alu64",
276};
277
278static const char *const bpf_alu_string[] = {
279 [BPF_ADD >> 4] = "+=",
280 [BPF_SUB >> 4] = "-=",
281 [BPF_MUL >> 4] = "*=",
282 [BPF_DIV >> 4] = "/=",
283 [BPF_OR >> 4] = "|=",
284 [BPF_AND >> 4] = "&=",
285 [BPF_LSH >> 4] = "<<=",
286 [BPF_RSH >> 4] = ">>=",
287 [BPF_NEG >> 4] = "neg",
288 [BPF_MOD >> 4] = "%=",
289 [BPF_XOR >> 4] = "^=",
290 [BPF_MOV >> 4] = "=",
291 [BPF_ARSH >> 4] = "s>>=",
292 [BPF_END >> 4] = "endian",
293};
294
295static const char *const bpf_ldst_string[] = {
296 [BPF_W >> 3] = "u32",
297 [BPF_H >> 3] = "u16",
298 [BPF_B >> 3] = "u8",
299 [BPF_DW >> 3] = "u64",
300};
301
302static const char *const bpf_jmp_string[] = {
303 [BPF_JA >> 4] = "jmp",
304 [BPF_JEQ >> 4] = "==",
305 [BPF_JGT >> 4] = ">",
306 [BPF_JGE >> 4] = ">=",
307 [BPF_JSET >> 4] = "&",
308 [BPF_JNE >> 4] = "!=",
309 [BPF_JSGT >> 4] = "s>",
310 [BPF_JSGE >> 4] = "s>=",
311 [BPF_CALL >> 4] = "call",
312 [BPF_EXIT >> 4] = "exit",
313};
314
315static void print_bpf_insn(struct bpf_insn *insn)
316{
317 u8 class = BPF_CLASS(insn->code);
318
319 if (class == BPF_ALU || class == BPF_ALU64) {
320 if (BPF_SRC(insn->code) == BPF_X)
321 verbose("(%02x) %sr%d %s %sr%d\n",
322 insn->code, class == BPF_ALU ? "(u32) " : "",
323 insn->dst_reg,
324 bpf_alu_string[BPF_OP(insn->code) >> 4],
325 class == BPF_ALU ? "(u32) " : "",
326 insn->src_reg);
327 else
328 verbose("(%02x) %sr%d %s %s%d\n",
329 insn->code, class == BPF_ALU ? "(u32) " : "",
330 insn->dst_reg,
331 bpf_alu_string[BPF_OP(insn->code) >> 4],
332 class == BPF_ALU ? "(u32) " : "",
333 insn->imm);
334 } else if (class == BPF_STX) {
335 if (BPF_MODE(insn->code) == BPF_MEM)
336 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
337 insn->code,
338 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
339 insn->dst_reg,
340 insn->off, insn->src_reg);
341 else if (BPF_MODE(insn->code) == BPF_XADD)
342 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
343 insn->code,
344 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
345 insn->dst_reg, insn->off,
346 insn->src_reg);
347 else
348 verbose("BUG_%02x\n", insn->code);
349 } else if (class == BPF_ST) {
350 if (BPF_MODE(insn->code) != BPF_MEM) {
351 verbose("BUG_st_%02x\n", insn->code);
352 return;
353 }
354 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
355 insn->code,
356 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
357 insn->dst_reg,
358 insn->off, insn->imm);
359 } else if (class == BPF_LDX) {
360 if (BPF_MODE(insn->code) != BPF_MEM) {
361 verbose("BUG_ldx_%02x\n", insn->code);
362 return;
363 }
364 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
365 insn->code, insn->dst_reg,
366 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
367 insn->src_reg, insn->off);
368 } else if (class == BPF_LD) {
369 if (BPF_MODE(insn->code) == BPF_ABS) {
370 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
371 insn->code,
372 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
373 insn->imm);
374 } else if (BPF_MODE(insn->code) == BPF_IND) {
375 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
376 insn->code,
377 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
378 insn->src_reg, insn->imm);
379 } else if (BPF_MODE(insn->code) == BPF_IMM) {
380 verbose("(%02x) r%d = 0x%x\n",
381 insn->code, insn->dst_reg, insn->imm);
382 } else {
383 verbose("BUG_ld_%02x\n", insn->code);
384 return;
385 }
386 } else if (class == BPF_JMP) {
387 u8 opcode = BPF_OP(insn->code);
388
389 if (opcode == BPF_CALL) {
390 verbose("(%02x) call %d\n", insn->code, insn->imm);
391 } else if (insn->code == (BPF_JMP | BPF_JA)) {
392 verbose("(%02x) goto pc%+d\n",
393 insn->code, insn->off);
394 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
395 verbose("(%02x) exit\n", insn->code);
396 } else if (BPF_SRC(insn->code) == BPF_X) {
397 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
398 insn->code, insn->dst_reg,
399 bpf_jmp_string[BPF_OP(insn->code) >> 4],
400 insn->src_reg, insn->off);
401 } else {
402 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
403 insn->code, insn->dst_reg,
404 bpf_jmp_string[BPF_OP(insn->code) >> 4],
405 insn->imm, insn->off);
406 }
407 } else {
408 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
409 }
410}
411
17a52670
AS		 412static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
413{
414 struct verifier_stack_elem *elem;
415 int insn_idx;
416
417 if (env->head == NULL)
418 return -1;
419
420 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
421 insn_idx = env->head->insn_idx;
422 if (prev_insn_idx)
423 *prev_insn_idx = env->head->prev_insn_idx;
424 elem = env->head->next;
425 kfree(env->head);
426 env->head = elem;
427 env->stack_size--;
428 return insn_idx;
429}
430
431static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
432 int prev_insn_idx)
433{
434 struct verifier_stack_elem *elem;
435
436 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
437 if (!elem)
438 goto err;
439
440 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
441 elem->insn_idx = insn_idx;
442 elem->prev_insn_idx = prev_insn_idx;
443 elem->next = env->head;
444 env->head = elem;
445 env->stack_size++;
446 if (env->stack_size > 1024) {
447 verbose("BPF program is too complex\n");
448 goto err;
449 }
450 return &elem->st;
451err:
452 /* pop all elements and return */
453 while (pop_stack(env, NULL) >= 0);
454 return NULL;
455}
456
457#define CALLER_SAVED_REGS 6
458static const int caller_saved[CALLER_SAVED_REGS] = {
459 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
460};
461
462static void init_reg_state(struct reg_state *regs)
463{
464 int i;
465
466 for (i = 0; i < MAX_BPF_REG; i++) {
467 regs[i].type = NOT_INIT;
468 regs[i].imm = 0;
469 regs[i].map_ptr = NULL;
470 }
471
472 /* frame pointer */
473 regs[BPF_REG_FP].type = FRAME_PTR;
474
475 /* 1st arg to a function */
476 regs[BPF_REG_1].type = PTR_TO_CTX;
477}
478
479static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
480{
481 BUG_ON(regno >= MAX_BPF_REG);
482 regs[regno].type = UNKNOWN_VALUE;
483 regs[regno].imm = 0;
484 regs[regno].map_ptr = NULL;
485}
486
487enum reg_arg_type {
488 SRC_OP, /* register is used as source operand */
489 DST_OP, /* register is used as destination operand */
490 DST_OP_NO_MARK /* same as above, check only, don't mark */
491};
492
493static int check_reg_arg(struct reg_state *regs, u32 regno,
494 enum reg_arg_type t)
495{
496 if (regno >= MAX_BPF_REG) {
497 verbose("R%d is invalid\n", regno);
498 return -EINVAL;
499 }
500
501 if (t == SRC_OP) {
502 /* check whether register used as source operand can be read */
503 if (regs[regno].type == NOT_INIT) {
504 verbose("R%d !read_ok\n", regno);
505 return -EACCES;
506 }
507 } else {
508 /* check whether register used as dest operand can be written to */
509 if (regno == BPF_REG_FP) {
510 verbose("frame pointer is read only\n");
511 return -EACCES;
512 }
513 if (t == DST_OP)
514 mark_reg_unknown_value(regs, regno);
515 }
516 return 0;
517}
518
519static int bpf_size_to_bytes(int bpf_size)
520{
521 if (bpf_size == BPF_W)
522 return 4;
523 else if (bpf_size == BPF_H)
524 return 2;
525 else if (bpf_size == BPF_B)
526 return 1;
527 else if (bpf_size == BPF_DW)
528 return 8;
529 else
530 return -EINVAL;
531}
532
533/* check_stack_read/write functions track spill/fill of registers,
534 * stack boundary and alignment are checked in check_mem_access()
535 */
536static int check_stack_write(struct verifier_state *state, int off, int size,
537 int value_regno)
538{
17a52670 539 int i;
9c399760
AS		 540 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
541 * so it's aligned access and [off, off + size) are within stack limits
542 */
17a52670
AS		 543
544 if (value_regno >= 0 &&
545 (state->regs[value_regno].type == PTR_TO_MAP_VALUE ||
546 state->regs[value_regno].type == PTR_TO_STACK ||
547 state->regs[value_regno].type == PTR_TO_CTX)) {
548
549 /* register containing pointer is being spilled into stack */
9c399760 550 if (size != BPF_REG_SIZE) {
17a52670
AS		 551 verbose("invalid size of register spill\n");
552 return -EACCES;
553 }
554
17a52670 555 /* save register state */
9c399760
AS		 556 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
557 state->regs[value_regno];
17a52670 558
9c399760
AS		 559 for (i = 0; i < BPF_REG_SIZE; i++)
560 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
561 } else {
17a52670 562 /* regular write of data into stack */
9c399760
AS		 563 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
564 (struct reg_state) {};
565
566 for (i = 0; i < size; i++)
567 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
17a52670
AS		 568 }
569 return 0;
570}
571
572static int check_stack_read(struct verifier_state *state, int off, int size,
573 int value_regno)
574{
9c399760 575 u8 *slot_type;
17a52670 576 int i;
17a52670 577
9c399760 578 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
17a52670 579
9c399760
AS		 580 if (slot_type[0] == STACK_SPILL) {
581 if (size != BPF_REG_SIZE) {
17a52670
AS		 582 verbose("invalid size of register spill\n");
583 return -EACCES;
584 }
9c399760
AS		 585 for (i = 1; i < BPF_REG_SIZE; i++) {
586 if (slot_type[i] != STACK_SPILL) {
17a52670
AS		 587 verbose("corrupted spill memory\n");
588 return -EACCES;
589 }
590 }
591
592 if (value_regno >= 0)
593 /* restore register state from stack */
9c399760
AS		 594 state->regs[value_regno] =
595 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
17a52670
AS		 596 return 0;
597 } else {
598 for (i = 0; i < size; i++) {
9c399760 599 if (slot_type[i] != STACK_MISC) {
17a52670
AS		 600 verbose("invalid read from stack off %d+%d size %d\n",
601 off, i, size);
602 return -EACCES;
603 }
604 }
605 if (value_regno >= 0)
606 /* have read misc data from the stack */
607 mark_reg_unknown_value(state->regs, value_regno);
608 return 0;
609 }
610}
611
612/* check read/write into map element returned by bpf_map_lookup_elem() */
613static int check_map_access(struct verifier_env *env, u32 regno, int off,
614 int size)
615{
616 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
617
618 if (off < 0 || off + size > map->value_size) {
619 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
620 map->value_size, off, size);
621 return -EACCES;
622 }
623 return 0;
624}
625
626/* check access to 'struct bpf_context' fields */
627static int check_ctx_access(struct verifier_env *env, int off, int size,
628 enum bpf_access_type t)
629{
630 if (env->prog->aux->ops->is_valid_access &&
631 env->prog->aux->ops->is_valid_access(off, size, t))
632 return 0;
633
634 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
635 return -EACCES;
636}
637
638/* check whether memory at (regno + off) is accessible for t = (read | write)
639 * if t==write, value_regno is a register which value is stored into memory
640 * if t==read, value_regno is a register which will receive the value from memory
641 * if t==write && value_regno==-1, some unknown value is stored into memory
642 * if t==read && value_regno==-1, don't care what we read from memory
643 */
644static int check_mem_access(struct verifier_env *env, u32 regno, int off,
645 int bpf_size, enum bpf_access_type t,
646 int value_regno)
647{
648 struct verifier_state *state = &env->cur_state;
649 int size, err = 0;
650
651 size = bpf_size_to_bytes(bpf_size);
652 if (size < 0)
653 return size;
654
655 if (off % size != 0) {
656 verbose("misaligned access off %d size %d\n", off, size);
657 return -EACCES;
658 }
659
660 if (state->regs[regno].type == PTR_TO_MAP_VALUE) {
661 err = check_map_access(env, regno, off, size);
662 if (!err && t == BPF_READ && value_regno >= 0)
663 mark_reg_unknown_value(state->regs, value_regno);
664
665 } else if (state->regs[regno].type == PTR_TO_CTX) {
666 err = check_ctx_access(env, off, size, t);
667 if (!err && t == BPF_READ && value_regno >= 0)
668 mark_reg_unknown_value(state->regs, value_regno);
669
670 } else if (state->regs[regno].type == FRAME_PTR) {
671 if (off >= 0 || off < -MAX_BPF_STACK) {
672 verbose("invalid stack off=%d size=%d\n", off, size);
673 return -EACCES;
674 }
675 if (t == BPF_WRITE)
676 err = check_stack_write(state, off, size, value_regno);
677 else
678 err = check_stack_read(state, off, size, value_regno);
679 } else {
680 verbose("R%d invalid mem access '%s'\n",
681 regno, reg_type_str[state->regs[regno].type]);
682 return -EACCES;
683 }
684 return err;
685}
686
687static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
688{
689 struct reg_state *regs = env->cur_state.regs;
690 int err;
691
692 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
693 insn->imm != 0) {
694 verbose("BPF_XADD uses reserved fields\n");
695 return -EINVAL;
696 }
697
698 /* check src1 operand */
699 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
700 if (err)
701 return err;
702
703 /* check src2 operand */
704 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
705 if (err)
706 return err;
707
708 /* check whether atomic_add can read the memory */
709 err = check_mem_access(env, insn->dst_reg, insn->off,
710 BPF_SIZE(insn->code), BPF_READ, -1);
711 if (err)
712 return err;
713
714 /* check whether atomic_add can write into the same memory */
715 return check_mem_access(env, insn->dst_reg, insn->off,
716 BPF_SIZE(insn->code), BPF_WRITE, -1);
717}
718
719/* when register 'regno' is passed into function that will read 'access_size'
720 * bytes from that pointer, make sure that it's within stack boundary
721 * and all elements of stack are initialized
722 */
723static int check_stack_boundary(struct verifier_env *env,
724 int regno, int access_size)
725{
726 struct verifier_state *state = &env->cur_state;
727 struct reg_state *regs = state->regs;
728 int off, i;
729
730 if (regs[regno].type != PTR_TO_STACK)
731 return -EACCES;
732
733 off = regs[regno].imm;
734 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
735 access_size <= 0) {
736 verbose("invalid stack type R%d off=%d access_size=%d\n",
737 regno, off, access_size);
738 return -EACCES;
739 }
740
741 for (i = 0; i < access_size; i++) {
9c399760 742 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
17a52670
AS		 743 verbose("invalid indirect read from stack off %d+%d size %d\n",
744 off, i, access_size);
745 return -EACCES;
746 }
747 }
748 return 0;
749}
750
751static int check_func_arg(struct verifier_env *env, u32 regno,
752 enum bpf_arg_type arg_type, struct bpf_map **mapp)
753{
754 struct reg_state *reg = env->cur_state.regs + regno;
755 enum bpf_reg_type expected_type;
756 int err = 0;
757
80f1d68c 758 if (arg_type == ARG_DONTCARE)
17a52670
AS		 759 return 0;
760
761 if (reg->type == NOT_INIT) {
762 verbose("R%d !read_ok\n", regno);
763 return -EACCES;
764 }
765
80f1d68c
DB		 766 if (arg_type == ARG_ANYTHING)
767 return 0;
768
17a52670
AS		 769 if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
770 arg_type == ARG_PTR_TO_MAP_VALUE) {
771 expected_type = PTR_TO_STACK;
772 } else if (arg_type == ARG_CONST_STACK_SIZE) {
773 expected_type = CONST_IMM;
774 } else if (arg_type == ARG_CONST_MAP_PTR) {
775 expected_type = CONST_PTR_TO_MAP;
608cd71a
AS		 776 } else if (arg_type == ARG_PTR_TO_CTX) {
777 expected_type = PTR_TO_CTX;
17a52670
AS		 778 } else {
779 verbose("unsupported arg_type %d\n", arg_type);
780 return -EFAULT;
781 }
782
783 if (reg->type != expected_type) {
784 verbose("R%d type=%s expected=%s\n", regno,
785 reg_type_str[reg->type], reg_type_str[expected_type]);
786 return -EACCES;
787 }
788
789 if (arg_type == ARG_CONST_MAP_PTR) {
790 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
791 *mapp = reg->map_ptr;
792
793 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
794 /* bpf_map_xxx(..., map_ptr, ..., key) call:
795 * check that [key, key + map->key_size) are within
796 * stack limits and initialized
797 */
798 if (!*mapp) {
799 /* in function declaration map_ptr must come before
800 * map_key, so that it's verified and known before
801 * we have to check map_key here. Otherwise it means
802 * that kernel subsystem misconfigured verifier
803 */
804 verbose("invalid map_ptr to access map->key\n");
805 return -EACCES;
806 }
807 err = check_stack_boundary(env, regno, (*mapp)->key_size);
808
809 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
810 /* bpf_map_xxx(..., map_ptr, ..., value) call:
811 * check [value, value + map->value_size) validity
812 */
813 if (!*mapp) {
814 /* kernel subsystem misconfigured verifier */
815 verbose("invalid map_ptr to access map->value\n");
816 return -EACCES;
817 }
818 err = check_stack_boundary(env, regno, (*mapp)->value_size);
819
820 } else if (arg_type == ARG_CONST_STACK_SIZE) {
821 /* bpf_xxx(..., buf, len) call will access 'len' bytes
822 * from stack pointer 'buf'. Check it
823 * note: regno == len, regno - 1 == buf
824 */
825 if (regno == 0) {
826 /* kernel subsystem misconfigured verifier */
827 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
828 return -EACCES;
829 }
830 err = check_stack_boundary(env, regno - 1, reg->imm);
831 }
832
833 return err;
834}
835
836static int check_call(struct verifier_env *env, int func_id)
837{
838 struct verifier_state *state = &env->cur_state;
839 const struct bpf_func_proto *fn = NULL;
840 struct reg_state *regs = state->regs;
841 struct bpf_map *map = NULL;
842 struct reg_state *reg;
843 int i, err;
844
845 /* find function prototype */
846 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
847 verbose("invalid func %d\n", func_id);
848 return -EINVAL;
849 }
850
851 if (env->prog->aux->ops->get_func_proto)
852 fn = env->prog->aux->ops->get_func_proto(func_id);
853
854 if (!fn) {
855 verbose("unknown func %d\n", func_id);
856 return -EINVAL;
857 }
858
859 /* eBPF programs must be GPL compatible to use GPL-ed functions */
24701ece 860 if (!env->prog->gpl_compatible && fn->gpl_only) {
17a52670
AS		 861 verbose("cannot call GPL only function from proprietary program\n");
862 return -EINVAL;
863 }
864
865 /* check args */
866 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map);
867 if (err)
868 return err;
869 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map);
870 if (err)
871 return err;
872 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map);
873 if (err)
874 return err;
875 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map);
876 if (err)
877 return err;
878 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map);
879 if (err)
880 return err;
881
882 /* reset caller saved regs */
883 for (i = 0; i < CALLER_SAVED_REGS; i++) {
884 reg = regs + caller_saved[i];
885 reg->type = NOT_INIT;
886 reg->imm = 0;
887 }
888
889 /* update return register */
890 if (fn->ret_type == RET_INTEGER) {
891 regs[BPF_REG_0].type = UNKNOWN_VALUE;
892 } else if (fn->ret_type == RET_VOID) {
893 regs[BPF_REG_0].type = NOT_INIT;
894 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
895 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
896 /* remember map_ptr, so that check_map_access()
897 * can check 'value_size' boundary of memory access
898 * to map element returned from bpf_map_lookup_elem()
899 */
900 if (map == NULL) {
901 verbose("kernel subsystem misconfigured verifier\n");
902 return -EINVAL;
903 }
904 regs[BPF_REG_0].map_ptr = map;
905 } else {
906 verbose("unknown return type %d of func %d\n",
907 fn->ret_type, func_id);
908 return -EINVAL;
909 }
04fd61ab
AS		 910
911 if (map && map->map_type == BPF_MAP_TYPE_PROG_ARRAY &&
912 func_id != BPF_FUNC_tail_call)
913 /* prog_array map type needs extra care:
914 * only allow to pass it into bpf_tail_call() for now.
915 * bpf_map_delete_elem() can be allowed in the future,
916 * while bpf_map_update_elem() must only be done via syscall
917 */
918 return -EINVAL;
919
920 if (func_id == BPF_FUNC_tail_call &&
921 map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
922 /* don't allow any other map type to be passed into
923 * bpf_tail_call()
924 */
925 return -EINVAL;
926
17a52670
AS		 927 return 0;
928}
929
930/* check validity of 32-bit and 64-bit arithmetic operations */
931static int check_alu_op(struct reg_state *regs, struct bpf_insn *insn)
932{
933 u8 opcode = BPF_OP(insn->code);
934 int err;
935
936 if (opcode == BPF_END || opcode == BPF_NEG) {
937 if (opcode == BPF_NEG) {
938 if (BPF_SRC(insn->code) != 0 ||
939 insn->src_reg != BPF_REG_0 ||
940 insn->off != 0 || insn->imm != 0) {
941 verbose("BPF_NEG uses reserved fields\n");
942 return -EINVAL;
943 }
944 } else {
945 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
946 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
947 verbose("BPF_END uses reserved fields\n");
948 return -EINVAL;
949 }
950 }
951
952 /* check src operand */
953 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
954 if (err)
955 return err;
956
957 /* check dest operand */
958 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
959 if (err)
960 return err;
961
962 } else if (opcode == BPF_MOV) {
963
964 if (BPF_SRC(insn->code) == BPF_X) {
965 if (insn->imm != 0 || insn->off != 0) {
966 verbose("BPF_MOV uses reserved fields\n");
967 return -EINVAL;
968 }
969
970 /* check src operand */
971 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
972 if (err)
973 return err;
974 } else {
975 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
976 verbose("BPF_MOV uses reserved fields\n");
977 return -EINVAL;
978 }
979 }
980
981 /* check dest operand */
982 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
983 if (err)
984 return err;
985
986 if (BPF_SRC(insn->code) == BPF_X) {
987 if (BPF_CLASS(insn->code) == BPF_ALU64) {
988 /* case: R1 = R2
989 * copy register state to dest reg
990 */
991 regs[insn->dst_reg] = regs[insn->src_reg];
992 } else {
993 regs[insn->dst_reg].type = UNKNOWN_VALUE;
994 regs[insn->dst_reg].map_ptr = NULL;
995 }
996 } else {
997 /* case: R = imm
998 * remember the value we stored into this reg
999 */
1000 regs[insn->dst_reg].type = CONST_IMM;
1001 regs[insn->dst_reg].imm = insn->imm;
1002 }
1003
1004 } else if (opcode > BPF_END) {
1005 verbose("invalid BPF_ALU opcode %x\n", opcode);
1006 return -EINVAL;
1007
1008 } else { /* all other ALU ops: and, sub, xor, add, ... */
1009
1010 bool stack_relative = false;
1011
1012 if (BPF_SRC(insn->code) == BPF_X) {
1013 if (insn->imm != 0 || insn->off != 0) {
1014 verbose("BPF_ALU uses reserved fields\n");
1015 return -EINVAL;
1016 }
1017 /* check src1 operand */
1018 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1019 if (err)
1020 return err;
1021 } else {
1022 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1023 verbose("BPF_ALU uses reserved fields\n");
1024 return -EINVAL;
1025 }
1026 }
1027
1028 /* check src2 operand */
1029 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1030 if (err)
1031 return err;
1032
1033 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1034 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1035 verbose("div by zero\n");
1036 return -EINVAL;
1037 }
1038
1039 /* pattern match 'bpf_add Rx, imm' instruction */
1040 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1041 regs[insn->dst_reg].type == FRAME_PTR &&
1042 BPF_SRC(insn->code) == BPF_K)
1043 stack_relative = true;
1044
1045 /* check dest operand */
1046 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1047 if (err)
1048 return err;
1049
1050 if (stack_relative) {
1051 regs[insn->dst_reg].type = PTR_TO_STACK;
1052 regs[insn->dst_reg].imm = insn->imm;
1053 }
1054 }
1055
1056 return 0;
1057}
1058
1059static int check_cond_jmp_op(struct verifier_env *env,
1060 struct bpf_insn *insn, int *insn_idx)
1061{
1062 struct reg_state *regs = env->cur_state.regs;
1063 struct verifier_state *other_branch;
1064 u8 opcode = BPF_OP(insn->code);
1065 int err;
1066
1067 if (opcode > BPF_EXIT) {
1068 verbose("invalid BPF_JMP opcode %x\n", opcode);
1069 return -EINVAL;
1070 }
1071
1072 if (BPF_SRC(insn->code) == BPF_X) {
1073 if (insn->imm != 0) {
1074 verbose("BPF_JMP uses reserved fields\n");
1075 return -EINVAL;
1076 }
1077
1078 /* check src1 operand */
1079 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1080 if (err)
1081 return err;
1082 } else {
1083 if (insn->src_reg != BPF_REG_0) {
1084 verbose("BPF_JMP uses reserved fields\n");
1085 return -EINVAL;
1086 }
1087 }
1088
1089 /* check src2 operand */
1090 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1091 if (err)
1092 return err;
1093
1094 /* detect if R == 0 where R was initialized to zero earlier */
1095 if (BPF_SRC(insn->code) == BPF_K &&
1096 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1097 regs[insn->dst_reg].type == CONST_IMM &&
1098 regs[insn->dst_reg].imm == insn->imm) {
1099 if (opcode == BPF_JEQ) {
1100 /* if (imm == imm) goto pc+off;
1101 * only follow the goto, ignore fall-through
1102 */
1103 *insn_idx += insn->off;
1104 return 0;
1105 } else {
1106 /* if (imm != imm) goto pc+off;
1107 * only follow fall-through branch, since
1108 * that's where the program will go
1109 */
1110 return 0;
1111 }
1112 }
1113
1114 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1115 if (!other_branch)
1116 return -EFAULT;
1117
1118 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1119 if (BPF_SRC(insn->code) == BPF_K &&
1120 insn->imm == 0 && (opcode == BPF_JEQ ||
1121 opcode == BPF_JNE) &&
1122 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1123 if (opcode == BPF_JEQ) {
1124 /* next fallthrough insn can access memory via
1125 * this register
1126 */
1127 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1128 /* branch targer cannot access it, since reg == 0 */
1129 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1130 other_branch->regs[insn->dst_reg].imm = 0;
1131 } else {
1132 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1133 regs[insn->dst_reg].type = CONST_IMM;
1134 regs[insn->dst_reg].imm = 0;
1135 }
1136 } else if (BPF_SRC(insn->code) == BPF_K &&
1137 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1138
1139 if (opcode == BPF_JEQ) {
1140 /* detect if (R == imm) goto
1141 * and in the target state recognize that R = imm
1142 */
1143 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1144 other_branch->regs[insn->dst_reg].imm = insn->imm;
1145 } else {
1146 /* detect if (R != imm) goto
1147 * and in the fall-through state recognize that R = imm
1148 */
1149 regs[insn->dst_reg].type = CONST_IMM;
1150 regs[insn->dst_reg].imm = insn->imm;
1151 }
1152 }
1153 if (log_level)
1154 print_verifier_state(env);
1155 return 0;
1156}
1157
0246e64d
AS		 1158/* return the map pointer stored inside BPF_LD_IMM64 instruction */
1159static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1160{
1161 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1162
1163 return (struct bpf_map *) (unsigned long) imm64;
1164}
1165
17a52670
AS		 1166/* verify BPF_LD_IMM64 instruction */
1167static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1168{
1169 struct reg_state *regs = env->cur_state.regs;
1170 int err;
1171
1172 if (BPF_SIZE(insn->code) != BPF_DW) {
1173 verbose("invalid BPF_LD_IMM insn\n");
1174 return -EINVAL;
1175 }
1176 if (insn->off != 0) {
1177 verbose("BPF_LD_IMM64 uses reserved fields\n");
1178 return -EINVAL;
1179 }
1180
1181 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1182 if (err)
1183 return err;
1184
1185 if (insn->src_reg == 0)
1186 /* generic move 64-bit immediate into a register */
1187 return 0;
1188
1189 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1190 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1191
1192 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1193 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1194 return 0;
1195}
1196
96be4325
DB		 1197static bool may_access_skb(enum bpf_prog_type type)
1198{
1199 switch (type) {
1200 case BPF_PROG_TYPE_SOCKET_FILTER:
1201 case BPF_PROG_TYPE_SCHED_CLS:
94caee8c 1202 case BPF_PROG_TYPE_SCHED_ACT:
96be4325
DB		 1203 return true;
1204 default:
1205 return false;
1206 }
1207}
1208
ddd872bc
AS		 1209/* verify safety of LD_ABS|LD_IND instructions:
1210 * - they can only appear in the programs where ctx == skb
1211 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1212 * preserve R6-R9, and store return value into R0
1213 *
1214 * Implicit input:
1215 * ctx == skb == R6 == CTX
1216 *
1217 * Explicit input:
1218 * SRC == any register
1219 * IMM == 32-bit immediate
1220 *
1221 * Output:
1222 * R0 - 8/16/32-bit skb data converted to cpu endianness
1223 */
1224static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1225{
1226 struct reg_state *regs = env->cur_state.regs;
1227 u8 mode = BPF_MODE(insn->code);
1228 struct reg_state *reg;
1229 int i, err;
1230
24701ece 1231 if (!may_access_skb(env->prog->type)) {
96be4325 1232 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n");
ddd872bc
AS		 1233 return -EINVAL;
1234 }
1235
1236 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1237 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1238 verbose("BPF_LD_ABS uses reserved fields\n");
1239 return -EINVAL;
1240 }
1241
1242 /* check whether implicit source operand (register R6) is readable */
1243 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1244 if (err)
1245 return err;
1246
1247 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1248 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1249 return -EINVAL;
1250 }
1251
1252 if (mode == BPF_IND) {
1253 /* check explicit source operand */
1254 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1255 if (err)
1256 return err;
1257 }
1258
1259 /* reset caller saved regs to unreadable */
1260 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1261 reg = regs + caller_saved[i];
1262 reg->type = NOT_INIT;
1263 reg->imm = 0;
1264 }
1265
1266 /* mark destination R0 register as readable, since it contains
1267 * the value fetched from the packet
1268 */
1269 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1270 return 0;
1271}
1272
475fb78f
AS		 1273/* non-recursive DFS pseudo code
1274 * 1 procedure DFS-iterative(G,v):
1275 * 2 label v as discovered
1276 * 3 let S be a stack
1277 * 4 S.push(v)
1278 * 5 while S is not empty
1279 * 6 t <- S.pop()
1280 * 7 if t is what we're looking for:
1281 * 8 return t
1282 * 9 for all edges e in G.adjacentEdges(t) do
1283 * 10 if edge e is already labelled
1284 * 11 continue with the next edge
1285 * 12 w <- G.adjacentVertex(t,e)
1286 * 13 if vertex w is not discovered and not explored
1287 * 14 label e as tree-edge
1288 * 15 label w as discovered
1289 * 16 S.push(w)
1290 * 17 continue at 5
1291 * 18 else if vertex w is discovered
1292 * 19 label e as back-edge
1293 * 20 else
1294 * 21 // vertex w is explored
1295 * 22 label e as forward- or cross-edge
1296 * 23 label t as explored
1297 * 24 S.pop()
1298 *
1299 * convention:
1300 * 0x10 - discovered
1301 * 0x11 - discovered and fall-through edge labelled
1302 * 0x12 - discovered and fall-through and branch edges labelled
1303 * 0x20 - explored
1304 */
1305
1306enum {
1307 DISCOVERED = 0x10,
1308 EXPLORED = 0x20,
1309 FALLTHROUGH = 1,
1310 BRANCH = 2,
1311};
1312
f1bca824
AS		 1313#define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1314
475fb78f
AS		 1315static int *insn_stack; /* stack of insns to process */
1316static int cur_stack; /* current stack index */
1317static int *insn_state;
1318
1319/* t, w, e - match pseudo-code above:
1320 * t - index of current instruction
1321 * w - next instruction
1322 * e - edge
1323 */
1324static int push_insn(int t, int w, int e, struct verifier_env *env)
1325{
1326 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1327 return 0;
1328
1329 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1330 return 0;
1331
1332 if (w < 0 || w >= env->prog->len) {
1333 verbose("jump out of range from insn %d to %d\n", t, w);
1334 return -EINVAL;
1335 }
1336
f1bca824
AS		 1337 if (e == BRANCH)
1338 /* mark branch target for state pruning */
1339 env->explored_states[w] = STATE_LIST_MARK;
1340
475fb78f
AS		 1341 if (insn_state[w] == 0) {
1342 /* tree-edge */
1343 insn_state[t] = DISCOVERED | e;
1344 insn_state[w] = DISCOVERED;
1345 if (cur_stack >= env->prog->len)
1346 return -E2BIG;
1347 insn_stack[cur_stack++] = w;
1348 return 1;
1349 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1350 verbose("back-edge from insn %d to %d\n", t, w);
1351 return -EINVAL;
1352 } else if (insn_state[w] == EXPLORED) {
1353 /* forward- or cross-edge */
1354 insn_state[t] = DISCOVERED | e;
1355 } else {
1356 verbose("insn state internal bug\n");
1357 return -EFAULT;
1358 }
1359 return 0;
1360}
1361
1362/* non-recursive depth-first-search to detect loops in BPF program
1363 * loop == back-edge in directed graph
1364 */
1365static int check_cfg(struct verifier_env *env)
1366{
1367 struct bpf_insn *insns = env->prog->insnsi;
1368 int insn_cnt = env->prog->len;
1369 int ret = 0;
1370 int i, t;
1371
1372 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1373 if (!insn_state)
1374 return -ENOMEM;
1375
1376 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1377 if (!insn_stack) {
1378 kfree(insn_state);
1379 return -ENOMEM;
1380 }
1381
1382 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1383 insn_stack[0] = 0; /* 0 is the first instruction */
1384 cur_stack = 1;
1385
1386peek_stack:
1387 if (cur_stack == 0)
1388 goto check_state;
1389 t = insn_stack[cur_stack - 1];
1390
1391 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1392 u8 opcode = BPF_OP(insns[t].code);
1393
1394 if (opcode == BPF_EXIT) {
1395 goto mark_explored;
1396 } else if (opcode == BPF_CALL) {
1397 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1398 if (ret == 1)
1399 goto peek_stack;
1400 else if (ret < 0)
1401 goto err_free;
1402 } else if (opcode == BPF_JA) {
1403 if (BPF_SRC(insns[t].code) != BPF_K) {
1404 ret = -EINVAL;
1405 goto err_free;
1406 }
1407 /* unconditional jump with single edge */
1408 ret = push_insn(t, t + insns[t].off + 1,
1409 FALLTHROUGH, env);
1410 if (ret == 1)
1411 goto peek_stack;
1412 else if (ret < 0)
1413 goto err_free;
f1bca824
AS		 1414 /* tell verifier to check for equivalent states
1415 * after every call and jump
1416 */
c3de6317
AS		 1417 if (t + 1 < insn_cnt)
1418 env->explored_states[t + 1] = STATE_LIST_MARK;
475fb78f
AS		 1419 } else {
1420 /* conditional jump with two edges */
1421 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1422 if (ret == 1)
1423 goto peek_stack;
1424 else if (ret < 0)
1425 goto err_free;
1426
1427 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1428 if (ret == 1)
1429 goto peek_stack;
1430 else if (ret < 0)
1431 goto err_free;
1432 }
1433 } else {
1434 /* all other non-branch instructions with single
1435 * fall-through edge
1436 */
1437 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1438 if (ret == 1)
1439 goto peek_stack;
1440 else if (ret < 0)
1441 goto err_free;
1442 }
1443
1444mark_explored:
1445 insn_state[t] = EXPLORED;
1446 if (cur_stack-- <= 0) {
1447 verbose("pop stack internal bug\n");
1448 ret = -EFAULT;
1449 goto err_free;
1450 }
1451 goto peek_stack;
1452
1453check_state:
1454 for (i = 0; i < insn_cnt; i++) {
1455 if (insn_state[i] != EXPLORED) {
1456 verbose("unreachable insn %d\n", i);
1457 ret = -EINVAL;
1458 goto err_free;
1459 }
1460 }
1461 ret = 0; /* cfg looks good */
1462
1463err_free:
1464 kfree(insn_state);
1465 kfree(insn_stack);
1466 return ret;
1467}
1468
f1bca824
AS		 1469/* compare two verifier states
1470 *
1471 * all states stored in state_list are known to be valid, since
1472 * verifier reached 'bpf_exit' instruction through them
1473 *
1474 * this function is called when verifier exploring different branches of
1475 * execution popped from the state stack. If it sees an old state that has
1476 * more strict register state and more strict stack state then this execution
1477 * branch doesn't need to be explored further, since verifier already
1478 * concluded that more strict state leads to valid finish.
1479 *
1480 * Therefore two states are equivalent if register state is more conservative
1481 * and explored stack state is more conservative than the current one.
1482 * Example:
1483 * explored current
1484 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1485 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1486 *
1487 * In other words if current stack state (one being explored) has more
1488 * valid slots than old one that already passed validation, it means
1489 * the verifier can stop exploring and conclude that current state is valid too
1490 *
1491 * Similarly with registers. If explored state has register type as invalid
1492 * whereas register type in current state is meaningful, it means that
1493 * the current state will reach 'bpf_exit' instruction safely
1494 */
1495static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1496{
1497 int i;
1498
1499 for (i = 0; i < MAX_BPF_REG; i++) {
1500 if (memcmp(&old->regs[i], &cur->regs[i],
1501 sizeof(old->regs[0])) != 0) {
1502 if (old->regs[i].type == NOT_INIT ||
32bf08a6
AS		 1503 (old->regs[i].type == UNKNOWN_VALUE &&
1504 cur->regs[i].type != NOT_INIT))
f1bca824
AS		 1505 continue;
1506 return false;
1507 }
1508 }
1509
1510 for (i = 0; i < MAX_BPF_STACK; i++) {
9c399760
AS		 1511 if (old->stack_slot_type[i] == STACK_INVALID)
1512 continue;
1513 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1514 /* Ex: old explored (safe) state has STACK_SPILL in
1515 * this stack slot, but current has has STACK_MISC ->
1516 * this verifier states are not equivalent,
1517 * return false to continue verification of this path
1518 */
f1bca824 1519 return false;
9c399760
AS		 1520 if (i % BPF_REG_SIZE)
1521 continue;
1522 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1523 &cur->spilled_regs[i / BPF_REG_SIZE],
1524 sizeof(old->spilled_regs[0])))
1525 /* when explored and current stack slot types are
1526 * the same, check that stored pointers types
1527 * are the same as well.
1528 * Ex: explored safe path could have stored
1529 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1530 * but current path has stored:
1531 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1532 * such verifier states are not equivalent.
1533 * return false to continue verification of this path
1534 */
1535 return false;
1536 else
1537 continue;
f1bca824
AS		 1538 }
1539 return true;
1540}
1541
1542static int is_state_visited(struct verifier_env *env, int insn_idx)
1543{
1544 struct verifier_state_list *new_sl;
1545 struct verifier_state_list *sl;
1546
1547 sl = env->explored_states[insn_idx];
1548 if (!sl)
1549 /* this 'insn_idx' instruction wasn't marked, so we will not
1550 * be doing state search here
1551 */
1552 return 0;
1553
1554 while (sl != STATE_LIST_MARK) {
1555 if (states_equal(&sl->state, &env->cur_state))
1556 /* reached equivalent register/stack state,
1557 * prune the search
1558 */
1559 return 1;
1560 sl = sl->next;
1561 }
1562
1563 /* there were no equivalent states, remember current one.
1564 * technically the current state is not proven to be safe yet,
1565 * but it will either reach bpf_exit (which means it's safe) or
1566 * it will be rejected. Since there are no loops, we won't be
1567 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1568 */
1569 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1570 if (!new_sl)
1571 return -ENOMEM;
1572
1573 /* add new state to the head of linked list */
1574 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1575 new_sl->next = env->explored_states[insn_idx];
1576 env->explored_states[insn_idx] = new_sl;
1577 return 0;
1578}
1579
17a52670
AS		 1580static int do_check(struct verifier_env *env)
1581{
1582 struct verifier_state *state = &env->cur_state;
1583 struct bpf_insn *insns = env->prog->insnsi;
1584 struct reg_state *regs = state->regs;
1585 int insn_cnt = env->prog->len;
1586 int insn_idx, prev_insn_idx = 0;
1587 int insn_processed = 0;
1588 bool do_print_state = false;
1589
1590 init_reg_state(regs);
1591 insn_idx = 0;
1592 for (;;) {
1593 struct bpf_insn *insn;
1594 u8 class;
1595 int err;
1596
1597 if (insn_idx >= insn_cnt) {
1598 verbose("invalid insn idx %d insn_cnt %d\n",
1599 insn_idx, insn_cnt);
1600 return -EFAULT;
1601 }
1602
1603 insn = &insns[insn_idx];
1604 class = BPF_CLASS(insn->code);
1605
1606 if (++insn_processed > 32768) {
1607 verbose("BPF program is too large. Proccessed %d insn\n",
1608 insn_processed);
1609 return -E2BIG;
1610 }
1611
f1bca824
AS		 1612 err = is_state_visited(env, insn_idx);
1613 if (err < 0)
1614 return err;
1615 if (err == 1) {
1616 /* found equivalent state, can prune the search */
1617 if (log_level) {
1618 if (do_print_state)
1619 verbose("\nfrom %d to %d: safe\n",
1620 prev_insn_idx, insn_idx);
1621 else
1622 verbose("%d: safe\n", insn_idx);
1623 }
1624 goto process_bpf_exit;
1625 }
1626
17a52670
AS		 1627 if (log_level && do_print_state) {
1628 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1629 print_verifier_state(env);
1630 do_print_state = false;
1631 }
1632
1633 if (log_level) {
1634 verbose("%d: ", insn_idx);
1635 print_bpf_insn(insn);
1636 }
1637
1638 if (class == BPF_ALU || class == BPF_ALU64) {
1639 err = check_alu_op(regs, insn);
1640 if (err)
1641 return err;
1642
1643 } else if (class == BPF_LDX) {
9bac3d6d
AS		 1644 enum bpf_reg_type src_reg_type;
1645
1646 /* check for reserved fields is already done */
1647
17a52670
AS		 1648 /* check src operand */
1649 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1650 if (err)
1651 return err;
1652
1653 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1654 if (err)
1655 return err;
1656
725f9dcd
AS		 1657 src_reg_type = regs[insn->src_reg].type;
1658
17a52670
AS		 1659 /* check that memory (src_reg + off) is readable,
1660 * the state of dst_reg will be updated by this func
1661 */
1662 err = check_mem_access(env, insn->src_reg, insn->off,
1663 BPF_SIZE(insn->code), BPF_READ,
1664 insn->dst_reg);
1665 if (err)
1666 return err;
1667
725f9dcd
AS		 1668 if (BPF_SIZE(insn->code) != BPF_W) {
1669 insn_idx++;
1670 continue;
1671 }
9bac3d6d 1672
725f9dcd 1673 if (insn->imm == 0) {
9bac3d6d
AS		 1674 /* saw a valid insn
1675 * dst_reg = *(u32 *)(src_reg + off)
1676 * use reserved 'imm' field to mark this insn
1677 */
1678 insn->imm = src_reg_type;
1679
1680 } else if (src_reg_type != insn->imm &&
1681 (src_reg_type == PTR_TO_CTX ||
1682 insn->imm == PTR_TO_CTX)) {
1683 /* ABuser program is trying to use the same insn
1684 * dst_reg = *(u32*) (src_reg + off)
1685 * with different pointer types:
1686 * src_reg == ctx in one branch and
1687 * src_reg == stack|map in some other branch.
1688 * Reject it.
1689 */
1690 verbose("same insn cannot be used with different pointers\n");
1691 return -EINVAL;
1692 }
1693
17a52670 1694 } else if (class == BPF_STX) {
d691f9e8
AS		 1695 enum bpf_reg_type dst_reg_type;
1696
17a52670
AS		 1697 if (BPF_MODE(insn->code) == BPF_XADD) {
1698 err = check_xadd(env, insn);
1699 if (err)
1700 return err;
1701 insn_idx++;
1702 continue;
1703 }
1704
17a52670
AS		 1705 /* check src1 operand */
1706 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1707 if (err)
1708 return err;
1709 /* check src2 operand */
1710 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1711 if (err)
1712 return err;
1713
d691f9e8
AS		 1714 dst_reg_type = regs[insn->dst_reg].type;
1715
17a52670
AS		 1716 /* check that memory (dst_reg + off) is writeable */
1717 err = check_mem_access(env, insn->dst_reg, insn->off,
1718 BPF_SIZE(insn->code), BPF_WRITE,
1719 insn->src_reg);
1720 if (err)
1721 return err;
1722
d691f9e8
AS		 1723 if (insn->imm == 0) {
1724 insn->imm = dst_reg_type;
1725 } else if (dst_reg_type != insn->imm &&
1726 (dst_reg_type == PTR_TO_CTX ||
1727 insn->imm == PTR_TO_CTX)) {
1728 verbose("same insn cannot be used with different pointers\n");
1729 return -EINVAL;
1730 }
1731
17a52670
AS		 1732 } else if (class == BPF_ST) {
1733 if (BPF_MODE(insn->code) != BPF_MEM ||
1734 insn->src_reg != BPF_REG_0) {
1735 verbose("BPF_ST uses reserved fields\n");
1736 return -EINVAL;
1737 }
1738 /* check src operand */
1739 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1740 if (err)
1741 return err;
1742
1743 /* check that memory (dst_reg + off) is writeable */
1744 err = check_mem_access(env, insn->dst_reg, insn->off,
1745 BPF_SIZE(insn->code), BPF_WRITE,
1746 -1);
1747 if (err)
1748 return err;
1749
1750 } else if (class == BPF_JMP) {
1751 u8 opcode = BPF_OP(insn->code);
1752
1753 if (opcode == BPF_CALL) {
1754 if (BPF_SRC(insn->code) != BPF_K ||
1755 insn->off != 0 ||
1756 insn->src_reg != BPF_REG_0 ||
1757 insn->dst_reg != BPF_REG_0) {
1758 verbose("BPF_CALL uses reserved fields\n");
1759 return -EINVAL;
1760 }
1761
1762 err = check_call(env, insn->imm);
1763 if (err)
1764 return err;
1765
1766 } else if (opcode == BPF_JA) {
1767 if (BPF_SRC(insn->code) != BPF_K ||
1768 insn->imm != 0 ||
1769 insn->src_reg != BPF_REG_0 ||
1770 insn->dst_reg != BPF_REG_0) {
1771 verbose("BPF_JA uses reserved fields\n");
1772 return -EINVAL;
1773 }
1774
1775 insn_idx += insn->off + 1;
1776 continue;
1777
1778 } else if (opcode == BPF_EXIT) {
1779 if (BPF_SRC(insn->code) != BPF_K ||
1780 insn->imm != 0 ||
1781 insn->src_reg != BPF_REG_0 ||
1782 insn->dst_reg != BPF_REG_0) {
1783 verbose("BPF_EXIT uses reserved fields\n");
1784 return -EINVAL;
1785 }
1786
1787 /* eBPF calling convetion is such that R0 is used
1788 * to return the value from eBPF program.
1789 * Make sure that it's readable at this time
1790 * of bpf_exit, which means that program wrote
1791 * something into it earlier
1792 */
1793 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1794 if (err)
1795 return err;
1796
f1bca824 1797process_bpf_exit:
17a52670
AS		 1798 insn_idx = pop_stack(env, &prev_insn_idx);
1799 if (insn_idx < 0) {
1800 break;
1801 } else {
1802 do_print_state = true;
1803 continue;
1804 }
1805 } else {
1806 err = check_cond_jmp_op(env, insn, &insn_idx);
1807 if (err)
1808 return err;
1809 }
1810 } else if (class == BPF_LD) {
1811 u8 mode = BPF_MODE(insn->code);
1812
1813 if (mode == BPF_ABS || mode == BPF_IND) {
ddd872bc
AS		 1814 err = check_ld_abs(env, insn);
1815 if (err)
1816 return err;
1817
17a52670
AS		 1818 } else if (mode == BPF_IMM) {
1819 err = check_ld_imm(env, insn);
1820 if (err)
1821 return err;
1822
1823 insn_idx++;
1824 } else {
1825 verbose("invalid BPF_LD mode\n");
1826 return -EINVAL;
1827 }
1828 } else {
1829 verbose("unknown insn class %d\n", class);
1830 return -EINVAL;
1831 }
1832
1833 insn_idx++;
1834 }
1835
1836 return 0;
1837}
1838
0246e64d
AS		 1839/* look for pseudo eBPF instructions that access map FDs and
1840 * replace them with actual map pointers
1841 */
1842static int replace_map_fd_with_map_ptr(struct verifier_env *env)
1843{
1844 struct bpf_insn *insn = env->prog->insnsi;
1845 int insn_cnt = env->prog->len;
1846 int i, j;
1847
1848 for (i = 0; i < insn_cnt; i++, insn++) {
9bac3d6d 1849 if (BPF_CLASS(insn->code) == BPF_LDX &&
d691f9e8 1850 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
9bac3d6d
AS		 1851 verbose("BPF_LDX uses reserved fields\n");
1852 return -EINVAL;
1853 }
1854
d691f9e8
AS		 1855 if (BPF_CLASS(insn->code) == BPF_STX &&
1856 ((BPF_MODE(insn->code) != BPF_MEM &&
1857 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
1858 verbose("BPF_STX uses reserved fields\n");
1859 return -EINVAL;
1860 }
1861
0246e64d
AS		 1862 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
1863 struct bpf_map *map;
1864 struct fd f;
1865
1866 if (i == insn_cnt - 1 || insn[1].code != 0 ||
1867 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
1868 insn[1].off != 0) {
1869 verbose("invalid bpf_ld_imm64 insn\n");
1870 return -EINVAL;
1871 }
1872
1873 if (insn->src_reg == 0)
1874 /* valid generic load 64-bit imm */
1875 goto next_insn;
1876
1877 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
1878 verbose("unrecognized bpf_ld_imm64 insn\n");
1879 return -EINVAL;
1880 }
1881
1882 f = fdget(insn->imm);
1883
1884 map = bpf_map_get(f);
1885 if (IS_ERR(map)) {
1886 verbose("fd %d is not pointing to valid bpf_map\n",
1887 insn->imm);
1888 fdput(f);
1889 return PTR_ERR(map);
1890 }
1891
1892 /* store map pointer inside BPF_LD_IMM64 instruction */
1893 insn[0].imm = (u32) (unsigned long) map;
1894 insn[1].imm = ((u64) (unsigned long) map) >> 32;
1895
1896 /* check whether we recorded this map already */
1897 for (j = 0; j < env->used_map_cnt; j++)
1898 if (env->used_maps[j] == map) {
1899 fdput(f);
1900 goto next_insn;
1901 }
1902
1903 if (env->used_map_cnt >= MAX_USED_MAPS) {
1904 fdput(f);
1905 return -E2BIG;
1906 }
1907
1908 /* remember this map */
1909 env->used_maps[env->used_map_cnt++] = map;
1910
1911 /* hold the map. If the program is rejected by verifier,
1912 * the map will be released by release_maps() or it
1913 * will be used by the valid program until it's unloaded
1914 * and all maps are released in free_bpf_prog_info()
1915 */
1916 atomic_inc(&map->refcnt);
1917
1918 fdput(f);
1919next_insn:
1920 insn++;
1921 i++;
1922 }
1923 }
1924
1925 /* now all pseudo BPF_LD_IMM64 instructions load valid
1926 * 'struct bpf_map *' into a register instead of user map_fd.
1927 * These pointers will be used later by verifier to validate map access.
1928 */
1929 return 0;
1930}
1931
1932/* drop refcnt of maps used by the rejected program */
1933static void release_maps(struct verifier_env *env)
1934{
1935 int i;
1936
1937 for (i = 0; i < env->used_map_cnt; i++)
1938 bpf_map_put(env->used_maps[i]);
1939}
1940
1941/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
1942static void convert_pseudo_ld_imm64(struct verifier_env *env)
1943{
1944 struct bpf_insn *insn = env->prog->insnsi;
1945 int insn_cnt = env->prog->len;
1946 int i;
1947
1948 for (i = 0; i < insn_cnt; i++, insn++)
1949 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
1950 insn->src_reg = 0;
1951}
1952
9bac3d6d
AS		 1953static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
1954{
1955 struct bpf_insn *insn = prog->insnsi;
1956 int insn_cnt = prog->len;
1957 int i;
1958
1959 for (i = 0; i < insn_cnt; i++, insn++) {
1960 if (BPF_CLASS(insn->code) != BPF_JMP ||
1961 BPF_OP(insn->code) == BPF_CALL ||
1962 BPF_OP(insn->code) == BPF_EXIT)
1963 continue;
1964
1965 /* adjust offset of jmps if necessary */
1966 if (i < pos && i + insn->off + 1 > pos)
1967 insn->off += delta;
1968 else if (i > pos && i + insn->off + 1 < pos)
1969 insn->off -= delta;
1970 }
1971}
1972
1973/* convert load instructions that access fields of 'struct __sk_buff'
1974 * into sequence of instructions that access fields of 'struct sk_buff'
1975 */
1976static int convert_ctx_accesses(struct verifier_env *env)
1977{
1978 struct bpf_insn *insn = env->prog->insnsi;
1979 int insn_cnt = env->prog->len;
1980 struct bpf_insn insn_buf[16];
1981 struct bpf_prog *new_prog;
1982 u32 cnt;
1983 int i;
d691f9e8 1984 enum bpf_access_type type;
9bac3d6d
AS		 1985
1986 if (!env->prog->aux->ops->convert_ctx_access)
1987 return 0;
1988
1989 for (i = 0; i < insn_cnt; i++, insn++) {
d691f9e8
AS		 1990 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
1991 type = BPF_READ;
1992 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
1993 type = BPF_WRITE;
1994 else
9bac3d6d
AS		 1995 continue;
1996
1997 if (insn->imm != PTR_TO_CTX) {
1998 /* clear internal mark */
1999 insn->imm = 0;
2000 continue;
2001 }
2002
2003 cnt = env->prog->aux->ops->
d691f9e8 2004 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
9bac3d6d
AS		 2005 insn->off, insn_buf);
2006 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2007 verbose("bpf verifier is misconfigured\n");
2008 return -EINVAL;
2009 }
2010
2011 if (cnt == 1) {
2012 memcpy(insn, insn_buf, sizeof(*insn));
2013 continue;
2014 }
2015
2016 /* several new insns need to be inserted. Make room for them */
2017 insn_cnt += cnt - 1;
2018 new_prog = bpf_prog_realloc(env->prog,
2019 bpf_prog_size(insn_cnt),
2020 GFP_USER);
2021 if (!new_prog)
2022 return -ENOMEM;
2023
2024 new_prog->len = insn_cnt;
2025
2026 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2027 sizeof(*insn) * (insn_cnt - i - cnt));
2028
2029 /* copy substitute insns in place of load instruction */
2030 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2031
2032 /* adjust branches in the whole program */
2033 adjust_branches(new_prog, i, cnt - 1);
2034
2035 /* keep walking new program and skip insns we just inserted */
2036 env->prog = new_prog;
2037 insn = new_prog->insnsi + i + cnt - 1;
2038 i += cnt - 1;
2039 }
2040
2041 return 0;
2042}
2043
f1bca824
AS		 2044static void free_states(struct verifier_env *env)
2045{
2046 struct verifier_state_list *sl, *sln;
2047 int i;
2048
2049 if (!env->explored_states)
2050 return;
2051
2052 for (i = 0; i < env->prog->len; i++) {
2053 sl = env->explored_states[i];
2054
2055 if (sl)
2056 while (sl != STATE_LIST_MARK) {
2057 sln = sl->next;
2058 kfree(sl);
2059 sl = sln;
2060 }
2061 }
2062
2063 kfree(env->explored_states);
2064}
2065
9bac3d6d 2066int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
51580e79 2067{
cbd35700
AS		 2068 char __user *log_ubuf = NULL;
2069 struct verifier_env *env;
51580e79
AS		 2070 int ret = -EINVAL;
2071
9bac3d6d 2072 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
cbd35700
AS		 2073 return -E2BIG;
2074
2075 /* 'struct verifier_env' can be global, but since it's not small,
2076 * allocate/free it every time bpf_check() is called
2077 */
2078 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2079 if (!env)
2080 return -ENOMEM;
2081
9bac3d6d 2082 env->prog = *prog;
0246e64d 2083
cbd35700
AS		 2084 /* grab the mutex to protect few globals used by verifier */
2085 mutex_lock(&bpf_verifier_lock);
2086
2087 if (attr->log_level || attr->log_buf || attr->log_size) {
2088 /* user requested verbose verifier output
2089 * and supplied buffer to store the verification trace
2090 */
2091 log_level = attr->log_level;
2092 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2093 log_size = attr->log_size;
2094 log_len = 0;
2095
2096 ret = -EINVAL;
2097 /* log_* values have to be sane */
2098 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2099 log_level == 0 || log_ubuf == NULL)
2100 goto free_env;
2101
2102 ret = -ENOMEM;
2103 log_buf = vmalloc(log_size);
2104 if (!log_buf)
2105 goto free_env;
2106 } else {
2107 log_level = 0;
2108 }
2109
0246e64d
AS		 2110 ret = replace_map_fd_with_map_ptr(env);
2111 if (ret < 0)
2112 goto skip_full_check;
2113
9bac3d6d 2114 env->explored_states = kcalloc(env->prog->len,
f1bca824
AS		 2115 sizeof(struct verifier_state_list *),
2116 GFP_USER);
2117 ret = -ENOMEM;
2118 if (!env->explored_states)
2119 goto skip_full_check;
2120
475fb78f
AS		 2121 ret = check_cfg(env);
2122 if (ret < 0)
2123 goto skip_full_check;
2124
17a52670 2125 ret = do_check(env);
cbd35700 2126
0246e64d 2127skip_full_check:
17a52670 2128 while (pop_stack(env, NULL) >= 0);
f1bca824 2129 free_states(env);
0246e64d 2130
9bac3d6d
AS		 2131 if (ret == 0)
2132 /* program is valid, convert *(u32*)(ctx + off) accesses */
2133 ret = convert_ctx_accesses(env);
2134
cbd35700
AS		 2135 if (log_level && log_len >= log_size - 1) {
2136 BUG_ON(log_len >= log_size);
2137 /* verifier log exceeded user supplied buffer */
2138 ret = -ENOSPC;
2139 /* fall through to return what was recorded */
2140 }
2141
2142 /* copy verifier log back to user space including trailing zero */
2143 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2144 ret = -EFAULT;
2145 goto free_log_buf;
2146 }
2147
0246e64d
AS		 2148 if (ret == 0 && env->used_map_cnt) {
2149 /* if program passed verifier, update used_maps in bpf_prog_info */
9bac3d6d
AS		 2150 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2151 sizeof(env->used_maps[0]),
2152 GFP_KERNEL);
0246e64d 2153
9bac3d6d 2154 if (!env->prog->aux->used_maps) {
0246e64d
AS		 2155 ret = -ENOMEM;
2156 goto free_log_buf;
2157 }
2158
9bac3d6d 2159 memcpy(env->prog->aux->used_maps, env->used_maps,
0246e64d 2160 sizeof(env->used_maps[0]) * env->used_map_cnt);
9bac3d6d 2161 env->prog->aux->used_map_cnt = env->used_map_cnt;
0246e64d
AS		 2162
2163 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2164 * bpf_ld_imm64 instructions
2165 */
2166 convert_pseudo_ld_imm64(env);
2167 }
cbd35700
AS		 2168
2169free_log_buf:
2170 if (log_level)
2171 vfree(log_buf);
2172free_env:
9bac3d6d 2173 if (!env->prog->aux->used_maps)
0246e64d
AS		 2174 /* if we didn't copy map pointers into bpf_prog_info, release
2175 * them now. Otherwise free_bpf_prog_info() will release them.
2176 */
2177 release_maps(env);
9bac3d6d 2178 *prog = env->prog;
cbd35700
AS		 2179 kfree(env);
2180 mutex_unlock(&bpf_verifier_lock);
51580e79
AS		 2181 return ret;
2182}
Linux 6.x block layer and io_uring tree(s)