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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 */
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 */
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 */
165struct 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 */
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
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 */
194struct 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 */
208static u32 log_level, log_size, log_len;
209static char *log_buf;
210
211static 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 */
217static __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' */
230static 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
242static void print_verifier_state(struct verifier_env *env)
243{
244 enum bpf_reg_type t;
245 int i;
246
247 for (i = 0; i < MAX_BPF_REG; i++) {
248 t = env->cur_state.regs[i].type;
249 if (t == NOT_INIT)
250 continue;
251 verbose(" R%d=%s", i, reg_type_str[t]);
252 if (t == CONST_IMM || t == PTR_TO_STACK)
253 verbose("%d", env->cur_state.regs[i].imm);
254 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
255 t == PTR_TO_MAP_VALUE_OR_NULL)
256 verbose("(ks=%d,vs=%d)",
257 env->cur_state.regs[i].map_ptr->key_size,
258 env->cur_state.regs[i].map_ptr->value_size);
259 }
260 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
261 if (env->cur_state.stack_slot_type[i] == STACK_SPILL)
262 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
263 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]);
264 }
265 verbose("\n");
266}
267
268static const char *const bpf_class_string[] = {
269 [BPF_LD] = "ld",
270 [BPF_LDX] = "ldx",
271 [BPF_ST] = "st",
272 [BPF_STX] = "stx",
273 [BPF_ALU] = "alu",
274 [BPF_JMP] = "jmp",
275 [BPF_RET] = "BUG",
276 [BPF_ALU64] = "alu64",
277};
278
279static const char *const bpf_alu_string[16] = {
280 [BPF_ADD >> 4] = "+=",
281 [BPF_SUB >> 4] = "-=",
282 [BPF_MUL >> 4] = "*=",
283 [BPF_DIV >> 4] = "/=",
284 [BPF_OR >> 4] = "|=",
285 [BPF_AND >> 4] = "&=",
286 [BPF_LSH >> 4] = "<<=",
287 [BPF_RSH >> 4] = ">>=",
288 [BPF_NEG >> 4] = "neg",
289 [BPF_MOD >> 4] = "%=",
290 [BPF_XOR >> 4] = "^=",
291 [BPF_MOV >> 4] = "=",
292 [BPF_ARSH >> 4] = "s>>=",
293 [BPF_END >> 4] = "endian",
294};
295
296static const char *const bpf_ldst_string[] = {
297 [BPF_W >> 3] = "u32",
298 [BPF_H >> 3] = "u16",
299 [BPF_B >> 3] = "u8",
300 [BPF_DW >> 3] = "u64",
301};
302
303static const char *const bpf_jmp_string[16] = {
304 [BPF_JA >> 4] = "jmp",
305 [BPF_JEQ >> 4] = "==",
306 [BPF_JGT >> 4] = ">",
307 [BPF_JGE >> 4] = ">=",
308 [BPF_JSET >> 4] = "&",
309 [BPF_JNE >> 4] = "!=",
310 [BPF_JSGT >> 4] = "s>",
311 [BPF_JSGE >> 4] = "s>=",
312 [BPF_CALL >> 4] = "call",
313 [BPF_EXIT >> 4] = "exit",
314};
315
316static void print_bpf_insn(struct bpf_insn *insn)
317{
318 u8 class = BPF_CLASS(insn->code);
319
320 if (class == BPF_ALU || class == BPF_ALU64) {
321 if (BPF_SRC(insn->code) == BPF_X)
322 verbose("(%02x) %sr%d %s %sr%d\n",
323 insn->code, class == BPF_ALU ? "(u32) " : "",
324 insn->dst_reg,
325 bpf_alu_string[BPF_OP(insn->code) >> 4],
326 class == BPF_ALU ? "(u32) " : "",
327 insn->src_reg);
328 else
329 verbose("(%02x) %sr%d %s %s%d\n",
330 insn->code, class == BPF_ALU ? "(u32) " : "",
331 insn->dst_reg,
332 bpf_alu_string[BPF_OP(insn->code) >> 4],
333 class == BPF_ALU ? "(u32) " : "",
334 insn->imm);
335 } else if (class == BPF_STX) {
336 if (BPF_MODE(insn->code) == BPF_MEM)
337 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
338 insn->code,
339 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
340 insn->dst_reg,
341 insn->off, insn->src_reg);
342 else if (BPF_MODE(insn->code) == BPF_XADD)
343 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
344 insn->code,
345 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
346 insn->dst_reg, insn->off,
347 insn->src_reg);
348 else
349 verbose("BUG_%02x\n", insn->code);
350 } else if (class == BPF_ST) {
351 if (BPF_MODE(insn->code) != BPF_MEM) {
352 verbose("BUG_st_%02x\n", insn->code);
353 return;
354 }
355 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
356 insn->code,
357 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
358 insn->dst_reg,
359 insn->off, insn->imm);
360 } else if (class == BPF_LDX) {
361 if (BPF_MODE(insn->code) != BPF_MEM) {
362 verbose("BUG_ldx_%02x\n", insn->code);
363 return;
364 }
365 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
366 insn->code, insn->dst_reg,
367 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
368 insn->src_reg, insn->off);
369 } else if (class == BPF_LD) {
370 if (BPF_MODE(insn->code) == BPF_ABS) {
371 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
372 insn->code,
373 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
374 insn->imm);
375 } else if (BPF_MODE(insn->code) == BPF_IND) {
376 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
377 insn->code,
378 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
379 insn->src_reg, insn->imm);
380 } else if (BPF_MODE(insn->code) == BPF_IMM) {
381 verbose("(%02x) r%d = 0x%x\n",
382 insn->code, insn->dst_reg, insn->imm);
383 } else {
384 verbose("BUG_ld_%02x\n", insn->code);
385 return;
386 }
387 } else if (class == BPF_JMP) {
388 u8 opcode = BPF_OP(insn->code);
389
390 if (opcode == BPF_CALL) {
391 verbose("(%02x) call %d\n", insn->code, insn->imm);
392 } else if (insn->code == (BPF_JMP | BPF_JA)) {
393 verbose("(%02x) goto pc%+d\n",
394 insn->code, insn->off);
395 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
396 verbose("(%02x) exit\n", insn->code);
397 } else if (BPF_SRC(insn->code) == BPF_X) {
398 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
399 insn->code, insn->dst_reg,
400 bpf_jmp_string[BPF_OP(insn->code) >> 4],
401 insn->src_reg, insn->off);
402 } else {
403 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
404 insn->code, insn->dst_reg,
405 bpf_jmp_string[BPF_OP(insn->code) >> 4],
406 insn->imm, insn->off);
407 }
408 } else {
409 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
410 }
411}
412
413static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
414{
415 struct verifier_stack_elem *elem;
416 int insn_idx;
417
418 if (env->head == NULL)
419 return -1;
420
421 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
422 insn_idx = env->head->insn_idx;
423 if (prev_insn_idx)
424 *prev_insn_idx = env->head->prev_insn_idx;
425 elem = env->head->next;
426 kfree(env->head);
427 env->head = elem;
428 env->stack_size--;
429 return insn_idx;
430}
431
432static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
433 int prev_insn_idx)
434{
435 struct verifier_stack_elem *elem;
436
437 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
438 if (!elem)
439 goto err;
440
441 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
442 elem->insn_idx = insn_idx;
443 elem->prev_insn_idx = prev_insn_idx;
444 elem->next = env->head;
445 env->head = elem;
446 env->stack_size++;
447 if (env->stack_size > 1024) {
448 verbose("BPF program is too complex\n");
449 goto err;
450 }
451 return &elem->st;
452err:
453 /* pop all elements and return */
454 while (pop_stack(env, NULL) >= 0);
455 return NULL;
456}
457
458#define CALLER_SAVED_REGS 6
459static const int caller_saved[CALLER_SAVED_REGS] = {
460 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
461};
462
463static void init_reg_state(struct reg_state *regs)
464{
465 int i;
466
467 for (i = 0; i < MAX_BPF_REG; i++) {
468 regs[i].type = NOT_INIT;
469 regs[i].imm = 0;
470 regs[i].map_ptr = NULL;
471 }
472
473 /* frame pointer */
474 regs[BPF_REG_FP].type = FRAME_PTR;
475
476 /* 1st arg to a function */
477 regs[BPF_REG_1].type = PTR_TO_CTX;
478}
479
480static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
481{
482 BUG_ON(regno >= MAX_BPF_REG);
483 regs[regno].type = UNKNOWN_VALUE;
484 regs[regno].imm = 0;
485 regs[regno].map_ptr = NULL;
486}
487
488enum reg_arg_type {
489 SRC_OP, /* register is used as source operand */
490 DST_OP, /* register is used as destination operand */
491 DST_OP_NO_MARK /* same as above, check only, don't mark */
492};
493
494static int check_reg_arg(struct reg_state *regs, u32 regno,
495 enum reg_arg_type t)
496{
497 if (regno >= MAX_BPF_REG) {
498 verbose("R%d is invalid\n", regno);
499 return -EINVAL;
500 }
501
502 if (t == SRC_OP) {
503 /* check whether register used as source operand can be read */
504 if (regs[regno].type == NOT_INIT) {
505 verbose("R%d !read_ok\n", regno);
506 return -EACCES;
507 }
508 } else {
509 /* check whether register used as dest operand can be written to */
510 if (regno == BPF_REG_FP) {
511 verbose("frame pointer is read only\n");
512 return -EACCES;
513 }
514 if (t == DST_OP)
515 mark_reg_unknown_value(regs, regno);
516 }
517 return 0;
518}
519
520static int bpf_size_to_bytes(int bpf_size)
521{
522 if (bpf_size == BPF_W)
523 return 4;
524 else if (bpf_size == BPF_H)
525 return 2;
526 else if (bpf_size == BPF_B)
527 return 1;
528 else if (bpf_size == BPF_DW)
529 return 8;
530 else
531 return -EINVAL;
532}
533
534static bool is_spillable_regtype(enum bpf_reg_type type)
535{
536 switch (type) {
537 case PTR_TO_MAP_VALUE:
538 case PTR_TO_MAP_VALUE_OR_NULL:
539 case PTR_TO_STACK:
540 case PTR_TO_CTX:
541 case FRAME_PTR:
542 case CONST_PTR_TO_MAP:
543 return true;
544 default:
545 return false;
546 }
547}
548
549/* check_stack_read/write functions track spill/fill of registers,
550 * stack boundary and alignment are checked in check_mem_access()
551 */
552static int check_stack_write(struct verifier_state *state, int off, int size,
553 int value_regno)
554{
555 int i;
556 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
557 * so it's aligned access and [off, off + size) are within stack limits
558 */
559
560 if (value_regno >= 0 &&
561 is_spillable_regtype(state->regs[value_regno].type)) {
562
563 /* register containing pointer is being spilled into stack */
564 if (size != BPF_REG_SIZE) {
565 verbose("invalid size of register spill\n");
566 return -EACCES;
567 }
568
569 /* save register state */
570 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
571 state->regs[value_regno];
572
573 for (i = 0; i < BPF_REG_SIZE; i++)
574 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
575 } else {
576 /* regular write of data into stack */
577 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
578 (struct reg_state) {};
579
580 for (i = 0; i < size; i++)
581 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
582 }
583 return 0;
584}
585
586static int check_stack_read(struct verifier_state *state, int off, int size,
587 int value_regno)
588{
589 u8 *slot_type;
590 int i;
591
592 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
593
594 if (slot_type[0] == STACK_SPILL) {
595 if (size != BPF_REG_SIZE) {
596 verbose("invalid size of register spill\n");
597 return -EACCES;
598 }
599 for (i = 1; i < BPF_REG_SIZE; i++) {
600 if (slot_type[i] != STACK_SPILL) {
601 verbose("corrupted spill memory\n");
602 return -EACCES;
603 }
604 }
605
606 if (value_regno >= 0)
607 /* restore register state from stack */
608 state->regs[value_regno] =
609 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
610 return 0;
611 } else {
612 for (i = 0; i < size; i++) {
613 if (slot_type[i] != STACK_MISC) {
614 verbose("invalid read from stack off %d+%d size %d\n",
615 off, i, size);
616 return -EACCES;
617 }
618 }
619 if (value_regno >= 0)
620 /* have read misc data from the stack */
621 mark_reg_unknown_value(state->regs, value_regno);
622 return 0;
623 }
624}
625
626/* check read/write into map element returned by bpf_map_lookup_elem() */
627static int check_map_access(struct verifier_env *env, u32 regno, int off,
628 int size)
629{
630 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
631
632 if (off < 0 || off + size > map->value_size) {
633 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
634 map->value_size, off, size);
635 return -EACCES;
636 }
637 return 0;
638}
639
640/* check access to 'struct bpf_context' fields */
641static int check_ctx_access(struct verifier_env *env, int off, int size,
642 enum bpf_access_type t)
643{
644 if (env->prog->aux->ops->is_valid_access &&
645 env->prog->aux->ops->is_valid_access(off, size, t))
646 return 0;
647
648 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
649 return -EACCES;
650}
651
652static bool is_pointer_value(struct verifier_env *env, int regno)
653{
654 if (env->allow_ptr_leaks)
655 return false;
656
657 switch (env->cur_state.regs[regno].type) {
658 case UNKNOWN_VALUE:
659 case CONST_IMM:
660 return false;
661 default:
662 return true;
663 }
664}
665
666/* check whether memory at (regno + off) is accessible for t = (read | write)
667 * if t==write, value_regno is a register which value is stored into memory
668 * if t==read, value_regno is a register which will receive the value from memory
669 * if t==write && value_regno==-1, some unknown value is stored into memory
670 * if t==read && value_regno==-1, don't care what we read from memory
671 */
672static int check_mem_access(struct verifier_env *env, u32 regno, int off,
673 int bpf_size, enum bpf_access_type t,
674 int value_regno)
675{
676 struct verifier_state *state = &env->cur_state;
677 int size, err = 0;
678
679 if (state->regs[regno].type == PTR_TO_STACK)
680 off += state->regs[regno].imm;
681
682 size = bpf_size_to_bytes(bpf_size);
683 if (size < 0)
684 return size;
685
686 if (off % size != 0) {
687 verbose("misaligned access off %d size %d\n", off, size);
688 return -EACCES;
689 }
690
691 if (state->regs[regno].type == PTR_TO_MAP_VALUE) {
692 if (t == BPF_WRITE && value_regno >= 0 &&
693 is_pointer_value(env, value_regno)) {
694 verbose("R%d leaks addr into map\n", value_regno);
695 return -EACCES;
696 }
697 err = check_map_access(env, regno, off, size);
698 if (!err && t == BPF_READ && value_regno >= 0)
699 mark_reg_unknown_value(state->regs, value_regno);
700
701 } else if (state->regs[regno].type == PTR_TO_CTX) {
702 if (t == BPF_WRITE && value_regno >= 0 &&
703 is_pointer_value(env, value_regno)) {
704 verbose("R%d leaks addr into ctx\n", value_regno);
705 return -EACCES;
706 }
707 err = check_ctx_access(env, off, size, t);
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 == FRAME_PTR ||
712 state->regs[regno].type == PTR_TO_STACK) {
713 if (off >= 0 || off < -MAX_BPF_STACK) {
714 verbose("invalid stack off=%d size=%d\n", off, size);
715 return -EACCES;
716 }
717 if (t == BPF_WRITE) {
718 if (!env->allow_ptr_leaks &&
719 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
720 size != BPF_REG_SIZE) {
721 verbose("attempt to corrupt spilled pointer on stack\n");
722 return -EACCES;
723 }
724 err = check_stack_write(state, off, size, value_regno);
725 } else {
726 err = check_stack_read(state, off, size, value_regno);
727 }
728 } else {
729 verbose("R%d invalid mem access '%s'\n",
730 regno, reg_type_str[state->regs[regno].type]);
731 return -EACCES;
732 }
733 return err;
734}
735
736static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
737{
738 struct reg_state *regs = env->cur_state.regs;
739 int err;
740
741 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
742 insn->imm != 0) {
743 verbose("BPF_XADD uses reserved fields\n");
744 return -EINVAL;
745 }
746
747 /* check src1 operand */
748 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
749 if (err)
750 return err;
751
752 /* check src2 operand */
753 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
754 if (err)
755 return err;
756
757 /* check whether atomic_add can read the memory */
758 err = check_mem_access(env, insn->dst_reg, insn->off,
759 BPF_SIZE(insn->code), BPF_READ, -1);
760 if (err)
761 return err;
762
763 /* check whether atomic_add can write into the same memory */
764 return check_mem_access(env, insn->dst_reg, insn->off,
765 BPF_SIZE(insn->code), BPF_WRITE, -1);
766}
767
768/* when register 'regno' is passed into function that will read 'access_size'
769 * bytes from that pointer, make sure that it's within stack boundary
770 * and all elements of stack are initialized
771 */
772static int check_stack_boundary(struct verifier_env *env, int regno,
773 int access_size, bool zero_size_allowed)
774{
775 struct verifier_state *state = &env->cur_state;
776 struct reg_state *regs = state->regs;
777 int off, i;
778
779 if (regs[regno].type != PTR_TO_STACK) {
780 if (zero_size_allowed && access_size == 0 &&
781 regs[regno].type == CONST_IMM &&
782 regs[regno].imm == 0)
783 return 0;
784
785 verbose("R%d type=%s expected=%s\n", regno,
786 reg_type_str[regs[regno].type],
787 reg_type_str[PTR_TO_STACK]);
788 return -EACCES;
789 }
790
791 off = regs[regno].imm;
792 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
793 access_size <= 0) {
794 verbose("invalid stack type R%d off=%d access_size=%d\n",
795 regno, off, access_size);
796 return -EACCES;
797 }
798
799 for (i = 0; i < access_size; i++) {
800 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
801 verbose("invalid indirect read from stack off %d+%d size %d\n",
802 off, i, access_size);
803 return -EACCES;
804 }
805 }
806 return 0;
807}
808
809static int check_func_arg(struct verifier_env *env, u32 regno,
810 enum bpf_arg_type arg_type, struct bpf_map **mapp)
811{
812 struct reg_state *reg = env->cur_state.regs + regno;
813 enum bpf_reg_type expected_type;
814 int err = 0;
815
816 if (arg_type == ARG_DONTCARE)
817 return 0;
818
819 if (reg->type == NOT_INIT) {
820 verbose("R%d !read_ok\n", regno);
821 return -EACCES;
822 }
823
824 if (arg_type == ARG_ANYTHING) {
825 if (is_pointer_value(env, regno)) {
826 verbose("R%d leaks addr into helper function\n", regno);
827 return -EACCES;
828 }
829 return 0;
830 }
831
832 if (arg_type == ARG_PTR_TO_MAP_KEY ||
833 arg_type == ARG_PTR_TO_MAP_VALUE) {
834 expected_type = PTR_TO_STACK;
835 } else if (arg_type == ARG_CONST_STACK_SIZE ||
836 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
837 expected_type = CONST_IMM;
838 } else if (arg_type == ARG_CONST_MAP_PTR) {
839 expected_type = CONST_PTR_TO_MAP;
840 } else if (arg_type == ARG_PTR_TO_CTX) {
841 expected_type = PTR_TO_CTX;
842 } else if (arg_type == ARG_PTR_TO_STACK) {
843 expected_type = PTR_TO_STACK;
844 /* One exception here. In case function allows for NULL to be
845 * passed in as argument, it's a CONST_IMM type. Final test
846 * happens during stack boundary checking.
847 */
848 if (reg->type == CONST_IMM && reg->imm == 0)
849 expected_type = CONST_IMM;
850 } else {
851 verbose("unsupported arg_type %d\n", arg_type);
852 return -EFAULT;
853 }
854
855 if (reg->type != expected_type) {
856 verbose("R%d type=%s expected=%s\n", regno,
857 reg_type_str[reg->type], reg_type_str[expected_type]);
858 return -EACCES;
859 }
860
861 if (arg_type == ARG_CONST_MAP_PTR) {
862 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
863 *mapp = reg->map_ptr;
864
865 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
866 /* bpf_map_xxx(..., map_ptr, ..., key) call:
867 * check that [key, key + map->key_size) are within
868 * stack limits and initialized
869 */
870 if (!*mapp) {
871 /* in function declaration map_ptr must come before
872 * map_key, so that it's verified and known before
873 * we have to check map_key here. Otherwise it means
874 * that kernel subsystem misconfigured verifier
875 */
876 verbose("invalid map_ptr to access map->key\n");
877 return -EACCES;
878 }
879 err = check_stack_boundary(env, regno, (*mapp)->key_size,
880 false);
881 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
882 /* bpf_map_xxx(..., map_ptr, ..., value) call:
883 * check [value, value + map->value_size) validity
884 */
885 if (!*mapp) {
886 /* kernel subsystem misconfigured verifier */
887 verbose("invalid map_ptr to access map->value\n");
888 return -EACCES;
889 }
890 err = check_stack_boundary(env, regno, (*mapp)->value_size,
891 false);
892 } else if (arg_type == ARG_CONST_STACK_SIZE ||
893 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
894 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
895
896 /* bpf_xxx(..., buf, len) call will access 'len' bytes
897 * from stack pointer 'buf'. Check it
898 * note: regno == len, regno - 1 == buf
899 */
900 if (regno == 0) {
901 /* kernel subsystem misconfigured verifier */
902 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
903 return -EACCES;
904 }
905 err = check_stack_boundary(env, regno - 1, reg->imm,
906 zero_size_allowed);
907 }
908
909 return err;
910}
911
912static int check_map_func_compatibility(struct bpf_map *map, int func_id)
913{
914 if (!map)
915 return 0;
916
917 /* We need a two way check, first is from map perspective ... */
918 switch (map->map_type) {
919 case BPF_MAP_TYPE_PROG_ARRAY:
920 if (func_id != BPF_FUNC_tail_call)
921 goto error;
922 break;
923 case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
924 if (func_id != BPF_FUNC_perf_event_read &&
925 func_id != BPF_FUNC_perf_event_output)
926 goto error;
927 break;
928 case BPF_MAP_TYPE_STACK_TRACE:
929 if (func_id != BPF_FUNC_get_stackid)
930 goto error;
931 break;
932 default:
933 break;
934 }
935
936 /* ... and second from the function itself. */
937 switch (func_id) {
938 case BPF_FUNC_tail_call:
939 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
940 goto error;
941 break;
942 case BPF_FUNC_perf_event_read:
943 case BPF_FUNC_perf_event_output:
944 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
945 goto error;
946 break;
947 case BPF_FUNC_get_stackid:
948 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
949 goto error;
950 break;
951 default:
952 break;
953 }
954
955 return 0;
956error:
957 verbose("cannot pass map_type %d into func %d\n",
958 map->map_type, func_id);
959 return -EINVAL;
960}
961
962static int check_call(struct verifier_env *env, int func_id)
963{
964 struct verifier_state *state = &env->cur_state;
965 const struct bpf_func_proto *fn = NULL;
966 struct reg_state *regs = state->regs;
967 struct bpf_map *map = NULL;
968 struct reg_state *reg;
969 int i, err;
970
971 /* find function prototype */
972 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
973 verbose("invalid func %d\n", func_id);
974 return -EINVAL;
975 }
976
977 if (env->prog->aux->ops->get_func_proto)
978 fn = env->prog->aux->ops->get_func_proto(func_id);
979
980 if (!fn) {
981 verbose("unknown func %d\n", func_id);
982 return -EINVAL;
983 }
984
985 /* eBPF programs must be GPL compatible to use GPL-ed functions */
986 if (!env->prog->gpl_compatible && fn->gpl_only) {
987 verbose("cannot call GPL only function from proprietary program\n");
988 return -EINVAL;
989 }
990
991 /* check args */
992 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map);
993 if (err)
994 return err;
995 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map);
996 if (err)
997 return err;
998 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map);
999 if (err)
1000 return err;
1001 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map);
1002 if (err)
1003 return err;
1004 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map);
1005 if (err)
1006 return err;
1007
1008 /* reset caller saved regs */
1009 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1010 reg = regs + caller_saved[i];
1011 reg->type = NOT_INIT;
1012 reg->imm = 0;
1013 }
1014
1015 /* update return register */
1016 if (fn->ret_type == RET_INTEGER) {
1017 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1018 } else if (fn->ret_type == RET_VOID) {
1019 regs[BPF_REG_0].type = NOT_INIT;
1020 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
1021 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
1022 /* remember map_ptr, so that check_map_access()
1023 * can check 'value_size' boundary of memory access
1024 * to map element returned from bpf_map_lookup_elem()
1025 */
1026 if (map == NULL) {
1027 verbose("kernel subsystem misconfigured verifier\n");
1028 return -EINVAL;
1029 }
1030 regs[BPF_REG_0].map_ptr = map;
1031 } else {
1032 verbose("unknown return type %d of func %d\n",
1033 fn->ret_type, func_id);
1034 return -EINVAL;
1035 }
1036
1037 err = check_map_func_compatibility(map, func_id);
1038 if (err)
1039 return err;
1040
1041 return 0;
1042}
1043
1044/* check validity of 32-bit and 64-bit arithmetic operations */
1045static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn)
1046{
1047 struct reg_state *regs = env->cur_state.regs;
1048 u8 opcode = BPF_OP(insn->code);
1049 int err;
1050
1051 if (opcode == BPF_END || opcode == BPF_NEG) {
1052 if (opcode == BPF_NEG) {
1053 if (BPF_SRC(insn->code) != 0 ||
1054 insn->src_reg != BPF_REG_0 ||
1055 insn->off != 0 || insn->imm != 0) {
1056 verbose("BPF_NEG uses reserved fields\n");
1057 return -EINVAL;
1058 }
1059 } else {
1060 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1061 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1062 verbose("BPF_END uses reserved fields\n");
1063 return -EINVAL;
1064 }
1065 }
1066
1067 /* check src operand */
1068 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1069 if (err)
1070 return err;
1071
1072 if (is_pointer_value(env, insn->dst_reg)) {
1073 verbose("R%d pointer arithmetic prohibited\n",
1074 insn->dst_reg);
1075 return -EACCES;
1076 }
1077
1078 /* check dest operand */
1079 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1080 if (err)
1081 return err;
1082
1083 } else if (opcode == BPF_MOV) {
1084
1085 if (BPF_SRC(insn->code) == BPF_X) {
1086 if (insn->imm != 0 || insn->off != 0) {
1087 verbose("BPF_MOV uses reserved fields\n");
1088 return -EINVAL;
1089 }
1090
1091 /* check src operand */
1092 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1093 if (err)
1094 return err;
1095 } else {
1096 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1097 verbose("BPF_MOV uses reserved fields\n");
1098 return -EINVAL;
1099 }
1100 }
1101
1102 /* check dest operand */
1103 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1104 if (err)
1105 return err;
1106
1107 if (BPF_SRC(insn->code) == BPF_X) {
1108 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1109 /* case: R1 = R2
1110 * copy register state to dest reg
1111 */
1112 regs[insn->dst_reg] = regs[insn->src_reg];
1113 } else {
1114 if (is_pointer_value(env, insn->src_reg)) {
1115 verbose("R%d partial copy of pointer\n",
1116 insn->src_reg);
1117 return -EACCES;
1118 }
1119 regs[insn->dst_reg].type = UNKNOWN_VALUE;
1120 regs[insn->dst_reg].map_ptr = NULL;
1121 }
1122 } else {
1123 /* case: R = imm
1124 * remember the value we stored into this reg
1125 */
1126 regs[insn->dst_reg].type = CONST_IMM;
1127 regs[insn->dst_reg].imm = insn->imm;
1128 }
1129
1130 } else if (opcode > BPF_END) {
1131 verbose("invalid BPF_ALU opcode %x\n", opcode);
1132 return -EINVAL;
1133
1134 } else { /* all other ALU ops: and, sub, xor, add, ... */
1135
1136 bool stack_relative = false;
1137
1138 if (BPF_SRC(insn->code) == BPF_X) {
1139 if (insn->imm != 0 || insn->off != 0) {
1140 verbose("BPF_ALU uses reserved fields\n");
1141 return -EINVAL;
1142 }
1143 /* check src1 operand */
1144 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1145 if (err)
1146 return err;
1147 } else {
1148 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1149 verbose("BPF_ALU uses reserved fields\n");
1150 return -EINVAL;
1151 }
1152 }
1153
1154 /* check src2 operand */
1155 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1156 if (err)
1157 return err;
1158
1159 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1160 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1161 verbose("div by zero\n");
1162 return -EINVAL;
1163 }
1164
1165 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1166 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1167 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1168
1169 if (insn->imm < 0 || insn->imm >= size) {
1170 verbose("invalid shift %d\n", insn->imm);
1171 return -EINVAL;
1172 }
1173 }
1174
1175 /* pattern match 'bpf_add Rx, imm' instruction */
1176 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1177 regs[insn->dst_reg].type == FRAME_PTR &&
1178 BPF_SRC(insn->code) == BPF_K) {
1179 stack_relative = true;
1180 } else if (is_pointer_value(env, insn->dst_reg)) {
1181 verbose("R%d pointer arithmetic prohibited\n",
1182 insn->dst_reg);
1183 return -EACCES;
1184 } else if (BPF_SRC(insn->code) == BPF_X &&
1185 is_pointer_value(env, insn->src_reg)) {
1186 verbose("R%d pointer arithmetic prohibited\n",
1187 insn->src_reg);
1188 return -EACCES;
1189 }
1190
1191 /* check dest operand */
1192 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1193 if (err)
1194 return err;
1195
1196 if (stack_relative) {
1197 regs[insn->dst_reg].type = PTR_TO_STACK;
1198 regs[insn->dst_reg].imm = insn->imm;
1199 }
1200 }
1201
1202 return 0;
1203}
1204
1205static int check_cond_jmp_op(struct verifier_env *env,
1206 struct bpf_insn *insn, int *insn_idx)
1207{
1208 struct reg_state *regs = env->cur_state.regs;
1209 struct verifier_state *other_branch;
1210 u8 opcode = BPF_OP(insn->code);
1211 int err;
1212
1213 if (opcode > BPF_EXIT) {
1214 verbose("invalid BPF_JMP opcode %x\n", opcode);
1215 return -EINVAL;
1216 }
1217
1218 if (BPF_SRC(insn->code) == BPF_X) {
1219 if (insn->imm != 0) {
1220 verbose("BPF_JMP uses reserved fields\n");
1221 return -EINVAL;
1222 }
1223
1224 /* check src1 operand */
1225 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1226 if (err)
1227 return err;
1228
1229 if (is_pointer_value(env, insn->src_reg)) {
1230 verbose("R%d pointer comparison prohibited\n",
1231 insn->src_reg);
1232 return -EACCES;
1233 }
1234 } else {
1235 if (insn->src_reg != BPF_REG_0) {
1236 verbose("BPF_JMP uses reserved fields\n");
1237 return -EINVAL;
1238 }
1239 }
1240
1241 /* check src2 operand */
1242 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1243 if (err)
1244 return err;
1245
1246 /* detect if R == 0 where R was initialized to zero earlier */
1247 if (BPF_SRC(insn->code) == BPF_K &&
1248 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1249 regs[insn->dst_reg].type == CONST_IMM &&
1250 regs[insn->dst_reg].imm == insn->imm) {
1251 if (opcode == BPF_JEQ) {
1252 /* if (imm == imm) goto pc+off;
1253 * only follow the goto, ignore fall-through
1254 */
1255 *insn_idx += insn->off;
1256 return 0;
1257 } else {
1258 /* if (imm != imm) goto pc+off;
1259 * only follow fall-through branch, since
1260 * that's where the program will go
1261 */
1262 return 0;
1263 }
1264 }
1265
1266 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1267 if (!other_branch)
1268 return -EFAULT;
1269
1270 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1271 if (BPF_SRC(insn->code) == BPF_K &&
1272 insn->imm == 0 && (opcode == BPF_JEQ ||
1273 opcode == BPF_JNE) &&
1274 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1275 if (opcode == BPF_JEQ) {
1276 /* next fallthrough insn can access memory via
1277 * this register
1278 */
1279 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1280 /* branch targer cannot access it, since reg == 0 */
1281 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1282 other_branch->regs[insn->dst_reg].imm = 0;
1283 } else {
1284 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1285 regs[insn->dst_reg].type = CONST_IMM;
1286 regs[insn->dst_reg].imm = 0;
1287 }
1288 } else if (is_pointer_value(env, insn->dst_reg)) {
1289 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
1290 return -EACCES;
1291 } else if (BPF_SRC(insn->code) == BPF_K &&
1292 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1293
1294 if (opcode == BPF_JEQ) {
1295 /* detect if (R == imm) goto
1296 * and in the target state recognize that R = imm
1297 */
1298 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1299 other_branch->regs[insn->dst_reg].imm = insn->imm;
1300 } else {
1301 /* detect if (R != imm) goto
1302 * and in the fall-through state recognize that R = imm
1303 */
1304 regs[insn->dst_reg].type = CONST_IMM;
1305 regs[insn->dst_reg].imm = insn->imm;
1306 }
1307 }
1308 if (log_level)
1309 print_verifier_state(env);
1310 return 0;
1311}
1312
1313/* return the map pointer stored inside BPF_LD_IMM64 instruction */
1314static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1315{
1316 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1317
1318 return (struct bpf_map *) (unsigned long) imm64;
1319}
1320
1321/* verify BPF_LD_IMM64 instruction */
1322static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1323{
1324 struct reg_state *regs = env->cur_state.regs;
1325 int err;
1326
1327 if (BPF_SIZE(insn->code) != BPF_DW) {
1328 verbose("invalid BPF_LD_IMM insn\n");
1329 return -EINVAL;
1330 }
1331 if (insn->off != 0) {
1332 verbose("BPF_LD_IMM64 uses reserved fields\n");
1333 return -EINVAL;
1334 }
1335
1336 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1337 if (err)
1338 return err;
1339
1340 if (insn->src_reg == 0)
1341 /* generic move 64-bit immediate into a register */
1342 return 0;
1343
1344 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1345 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1346
1347 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1348 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1349 return 0;
1350}
1351
1352static bool may_access_skb(enum bpf_prog_type type)
1353{
1354 switch (type) {
1355 case BPF_PROG_TYPE_SOCKET_FILTER:
1356 case BPF_PROG_TYPE_SCHED_CLS:
1357 case BPF_PROG_TYPE_SCHED_ACT:
1358 return true;
1359 default:
1360 return false;
1361 }
1362}
1363
1364/* verify safety of LD_ABS|LD_IND instructions:
1365 * - they can only appear in the programs where ctx == skb
1366 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1367 * preserve R6-R9, and store return value into R0
1368 *
1369 * Implicit input:
1370 * ctx == skb == R6 == CTX
1371 *
1372 * Explicit input:
1373 * SRC == any register
1374 * IMM == 32-bit immediate
1375 *
1376 * Output:
1377 * R0 - 8/16/32-bit skb data converted to cpu endianness
1378 */
1379static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1380{
1381 struct reg_state *regs = env->cur_state.regs;
1382 u8 mode = BPF_MODE(insn->code);
1383 struct reg_state *reg;
1384 int i, err;
1385
1386 if (!may_access_skb(env->prog->type)) {
1387 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n");
1388 return -EINVAL;
1389 }
1390
1391 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1392 BPF_SIZE(insn->code) == BPF_DW ||
1393 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1394 verbose("BPF_LD_ABS uses reserved fields\n");
1395 return -EINVAL;
1396 }
1397
1398 /* check whether implicit source operand (register R6) is readable */
1399 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1400 if (err)
1401 return err;
1402
1403 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1404 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1405 return -EINVAL;
1406 }
1407
1408 if (mode == BPF_IND) {
1409 /* check explicit source operand */
1410 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1411 if (err)
1412 return err;
1413 }
1414
1415 /* reset caller saved regs to unreadable */
1416 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1417 reg = regs + caller_saved[i];
1418 reg->type = NOT_INIT;
1419 reg->imm = 0;
1420 }
1421
1422 /* mark destination R0 register as readable, since it contains
1423 * the value fetched from the packet
1424 */
1425 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1426 return 0;
1427}
1428
1429/* non-recursive DFS pseudo code
1430 * 1 procedure DFS-iterative(G,v):
1431 * 2 label v as discovered
1432 * 3 let S be a stack
1433 * 4 S.push(v)
1434 * 5 while S is not empty
1435 * 6 t <- S.pop()
1436 * 7 if t is what we're looking for:
1437 * 8 return t
1438 * 9 for all edges e in G.adjacentEdges(t) do
1439 * 10 if edge e is already labelled
1440 * 11 continue with the next edge
1441 * 12 w <- G.adjacentVertex(t,e)
1442 * 13 if vertex w is not discovered and not explored
1443 * 14 label e as tree-edge
1444 * 15 label w as discovered
1445 * 16 S.push(w)
1446 * 17 continue at 5
1447 * 18 else if vertex w is discovered
1448 * 19 label e as back-edge
1449 * 20 else
1450 * 21 // vertex w is explored
1451 * 22 label e as forward- or cross-edge
1452 * 23 label t as explored
1453 * 24 S.pop()
1454 *
1455 * convention:
1456 * 0x10 - discovered
1457 * 0x11 - discovered and fall-through edge labelled
1458 * 0x12 - discovered and fall-through and branch edges labelled
1459 * 0x20 - explored
1460 */
1461
1462enum {
1463 DISCOVERED = 0x10,
1464 EXPLORED = 0x20,
1465 FALLTHROUGH = 1,
1466 BRANCH = 2,
1467};
1468
1469#define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1470
1471static int *insn_stack; /* stack of insns to process */
1472static int cur_stack; /* current stack index */
1473static int *insn_state;
1474
1475/* t, w, e - match pseudo-code above:
1476 * t - index of current instruction
1477 * w - next instruction
1478 * e - edge
1479 */
1480static int push_insn(int t, int w, int e, struct verifier_env *env)
1481{
1482 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1483 return 0;
1484
1485 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1486 return 0;
1487
1488 if (w < 0 || w >= env->prog->len) {
1489 verbose("jump out of range from insn %d to %d\n", t, w);
1490 return -EINVAL;
1491 }
1492
1493 if (e == BRANCH)
1494 /* mark branch target for state pruning */
1495 env->explored_states[w] = STATE_LIST_MARK;
1496
1497 if (insn_state[w] == 0) {
1498 /* tree-edge */
1499 insn_state[t] = DISCOVERED | e;
1500 insn_state[w] = DISCOVERED;
1501 if (cur_stack >= env->prog->len)
1502 return -E2BIG;
1503 insn_stack[cur_stack++] = w;
1504 return 1;
1505 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1506 verbose("back-edge from insn %d to %d\n", t, w);
1507 return -EINVAL;
1508 } else if (insn_state[w] == EXPLORED) {
1509 /* forward- or cross-edge */
1510 insn_state[t] = DISCOVERED | e;
1511 } else {
1512 verbose("insn state internal bug\n");
1513 return -EFAULT;
1514 }
1515 return 0;
1516}
1517
1518/* non-recursive depth-first-search to detect loops in BPF program
1519 * loop == back-edge in directed graph
1520 */
1521static int check_cfg(struct verifier_env *env)
1522{
1523 struct bpf_insn *insns = env->prog->insnsi;
1524 int insn_cnt = env->prog->len;
1525 int ret = 0;
1526 int i, t;
1527
1528 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1529 if (!insn_state)
1530 return -ENOMEM;
1531
1532 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1533 if (!insn_stack) {
1534 kfree(insn_state);
1535 return -ENOMEM;
1536 }
1537
1538 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1539 insn_stack[0] = 0; /* 0 is the first instruction */
1540 cur_stack = 1;
1541
1542peek_stack:
1543 if (cur_stack == 0)
1544 goto check_state;
1545 t = insn_stack[cur_stack - 1];
1546
1547 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1548 u8 opcode = BPF_OP(insns[t].code);
1549
1550 if (opcode == BPF_EXIT) {
1551 goto mark_explored;
1552 } else if (opcode == BPF_CALL) {
1553 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1554 if (ret == 1)
1555 goto peek_stack;
1556 else if (ret < 0)
1557 goto err_free;
1558 } else if (opcode == BPF_JA) {
1559 if (BPF_SRC(insns[t].code) != BPF_K) {
1560 ret = -EINVAL;
1561 goto err_free;
1562 }
1563 /* unconditional jump with single edge */
1564 ret = push_insn(t, t + insns[t].off + 1,
1565 FALLTHROUGH, env);
1566 if (ret == 1)
1567 goto peek_stack;
1568 else if (ret < 0)
1569 goto err_free;
1570 /* tell verifier to check for equivalent states
1571 * after every call and jump
1572 */
1573 if (t + 1 < insn_cnt)
1574 env->explored_states[t + 1] = STATE_LIST_MARK;
1575 } else {
1576 /* conditional jump with two edges */
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 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1584 if (ret == 1)
1585 goto peek_stack;
1586 else if (ret < 0)
1587 goto err_free;
1588 }
1589 } else {
1590 /* all other non-branch instructions with single
1591 * fall-through edge
1592 */
1593 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1594 if (ret == 1)
1595 goto peek_stack;
1596 else if (ret < 0)
1597 goto err_free;
1598 }
1599
1600mark_explored:
1601 insn_state[t] = EXPLORED;
1602 if (cur_stack-- <= 0) {
1603 verbose("pop stack internal bug\n");
1604 ret = -EFAULT;
1605 goto err_free;
1606 }
1607 goto peek_stack;
1608
1609check_state:
1610 for (i = 0; i < insn_cnt; i++) {
1611 if (insn_state[i] != EXPLORED) {
1612 verbose("unreachable insn %d\n", i);
1613 ret = -EINVAL;
1614 goto err_free;
1615 }
1616 }
1617 ret = 0; /* cfg looks good */
1618
1619err_free:
1620 kfree(insn_state);
1621 kfree(insn_stack);
1622 return ret;
1623}
1624
1625/* compare two verifier states
1626 *
1627 * all states stored in state_list are known to be valid, since
1628 * verifier reached 'bpf_exit' instruction through them
1629 *
1630 * this function is called when verifier exploring different branches of
1631 * execution popped from the state stack. If it sees an old state that has
1632 * more strict register state and more strict stack state then this execution
1633 * branch doesn't need to be explored further, since verifier already
1634 * concluded that more strict state leads to valid finish.
1635 *
1636 * Therefore two states are equivalent if register state is more conservative
1637 * and explored stack state is more conservative than the current one.
1638 * Example:
1639 * explored current
1640 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1641 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1642 *
1643 * In other words if current stack state (one being explored) has more
1644 * valid slots than old one that already passed validation, it means
1645 * the verifier can stop exploring and conclude that current state is valid too
1646 *
1647 * Similarly with registers. If explored state has register type as invalid
1648 * whereas register type in current state is meaningful, it means that
1649 * the current state will reach 'bpf_exit' instruction safely
1650 */
1651static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1652{
1653 int i;
1654
1655 for (i = 0; i < MAX_BPF_REG; i++) {
1656 if (memcmp(&old->regs[i], &cur->regs[i],
1657 sizeof(old->regs[0])) != 0) {
1658 if (old->regs[i].type == NOT_INIT ||
1659 (old->regs[i].type == UNKNOWN_VALUE &&
1660 cur->regs[i].type != NOT_INIT))
1661 continue;
1662 return false;
1663 }
1664 }
1665
1666 for (i = 0; i < MAX_BPF_STACK; i++) {
1667 if (old->stack_slot_type[i] == STACK_INVALID)
1668 continue;
1669 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1670 /* Ex: old explored (safe) state has STACK_SPILL in
1671 * this stack slot, but current has has STACK_MISC ->
1672 * this verifier states are not equivalent,
1673 * return false to continue verification of this path
1674 */
1675 return false;
1676 if (i % BPF_REG_SIZE)
1677 continue;
1678 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1679 &cur->spilled_regs[i / BPF_REG_SIZE],
1680 sizeof(old->spilled_regs[0])))
1681 /* when explored and current stack slot types are
1682 * the same, check that stored pointers types
1683 * are the same as well.
1684 * Ex: explored safe path could have stored
1685 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1686 * but current path has stored:
1687 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1688 * such verifier states are not equivalent.
1689 * return false to continue verification of this path
1690 */
1691 return false;
1692 else
1693 continue;
1694 }
1695 return true;
1696}
1697
1698static int is_state_visited(struct verifier_env *env, int insn_idx)
1699{
1700 struct verifier_state_list *new_sl;
1701 struct verifier_state_list *sl;
1702
1703 sl = env->explored_states[insn_idx];
1704 if (!sl)
1705 /* this 'insn_idx' instruction wasn't marked, so we will not
1706 * be doing state search here
1707 */
1708 return 0;
1709
1710 while (sl != STATE_LIST_MARK) {
1711 if (states_equal(&sl->state, &env->cur_state))
1712 /* reached equivalent register/stack state,
1713 * prune the search
1714 */
1715 return 1;
1716 sl = sl->next;
1717 }
1718
1719 /* there were no equivalent states, remember current one.
1720 * technically the current state is not proven to be safe yet,
1721 * but it will either reach bpf_exit (which means it's safe) or
1722 * it will be rejected. Since there are no loops, we won't be
1723 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1724 */
1725 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1726 if (!new_sl)
1727 return -ENOMEM;
1728
1729 /* add new state to the head of linked list */
1730 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1731 new_sl->next = env->explored_states[insn_idx];
1732 env->explored_states[insn_idx] = new_sl;
1733 return 0;
1734}
1735
1736static int do_check(struct verifier_env *env)
1737{
1738 struct verifier_state *state = &env->cur_state;
1739 struct bpf_insn *insns = env->prog->insnsi;
1740 struct reg_state *regs = state->regs;
1741 int insn_cnt = env->prog->len;
1742 int insn_idx, prev_insn_idx = 0;
1743 int insn_processed = 0;
1744 bool do_print_state = false;
1745
1746 init_reg_state(regs);
1747 insn_idx = 0;
1748 for (;;) {
1749 struct bpf_insn *insn;
1750 u8 class;
1751 int err;
1752
1753 if (insn_idx >= insn_cnt) {
1754 verbose("invalid insn idx %d insn_cnt %d\n",
1755 insn_idx, insn_cnt);
1756 return -EFAULT;
1757 }
1758
1759 insn = &insns[insn_idx];
1760 class = BPF_CLASS(insn->code);
1761
1762 if (++insn_processed > 32768) {
1763 verbose("BPF program is too large. Proccessed %d insn\n",
1764 insn_processed);
1765 return -E2BIG;
1766 }
1767
1768 err = is_state_visited(env, insn_idx);
1769 if (err < 0)
1770 return err;
1771 if (err == 1) {
1772 /* found equivalent state, can prune the search */
1773 if (log_level) {
1774 if (do_print_state)
1775 verbose("\nfrom %d to %d: safe\n",
1776 prev_insn_idx, insn_idx);
1777 else
1778 verbose("%d: safe\n", insn_idx);
1779 }
1780 goto process_bpf_exit;
1781 }
1782
1783 if (log_level && do_print_state) {
1784 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1785 print_verifier_state(env);
1786 do_print_state = false;
1787 }
1788
1789 if (log_level) {
1790 verbose("%d: ", insn_idx);
1791 print_bpf_insn(insn);
1792 }
1793
1794 if (class == BPF_ALU || class == BPF_ALU64) {
1795 err = check_alu_op(env, insn);
1796 if (err)
1797 return err;
1798
1799 } else if (class == BPF_LDX) {
1800 enum bpf_reg_type src_reg_type;
1801
1802 /* check for reserved fields is already done */
1803
1804 /* check src operand */
1805 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1806 if (err)
1807 return err;
1808
1809 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1810 if (err)
1811 return err;
1812
1813 src_reg_type = regs[insn->src_reg].type;
1814
1815 /* check that memory (src_reg + off) is readable,
1816 * the state of dst_reg will be updated by this func
1817 */
1818 err = check_mem_access(env, insn->src_reg, insn->off,
1819 BPF_SIZE(insn->code), BPF_READ,
1820 insn->dst_reg);
1821 if (err)
1822 return err;
1823
1824 if (BPF_SIZE(insn->code) != BPF_W) {
1825 insn_idx++;
1826 continue;
1827 }
1828
1829 if (insn->imm == 0) {
1830 /* saw a valid insn
1831 * dst_reg = *(u32 *)(src_reg + off)
1832 * use reserved 'imm' field to mark this insn
1833 */
1834 insn->imm = src_reg_type;
1835
1836 } else if (src_reg_type != insn->imm &&
1837 (src_reg_type == PTR_TO_CTX ||
1838 insn->imm == PTR_TO_CTX)) {
1839 /* ABuser program is trying to use the same insn
1840 * dst_reg = *(u32*) (src_reg + off)
1841 * with different pointer types:
1842 * src_reg == ctx in one branch and
1843 * src_reg == stack|map in some other branch.
1844 * Reject it.
1845 */
1846 verbose("same insn cannot be used with different pointers\n");
1847 return -EINVAL;
1848 }
1849
1850 } else if (class == BPF_STX) {
1851 enum bpf_reg_type dst_reg_type;
1852
1853 if (BPF_MODE(insn->code) == BPF_XADD) {
1854 err = check_xadd(env, insn);
1855 if (err)
1856 return err;
1857 insn_idx++;
1858 continue;
1859 }
1860
1861 /* check src1 operand */
1862 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1863 if (err)
1864 return err;
1865 /* check src2 operand */
1866 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1867 if (err)
1868 return err;
1869
1870 dst_reg_type = regs[insn->dst_reg].type;
1871
1872 /* check that memory (dst_reg + off) is writeable */
1873 err = check_mem_access(env, insn->dst_reg, insn->off,
1874 BPF_SIZE(insn->code), BPF_WRITE,
1875 insn->src_reg);
1876 if (err)
1877 return err;
1878
1879 if (insn->imm == 0) {
1880 insn->imm = dst_reg_type;
1881 } else if (dst_reg_type != insn->imm &&
1882 (dst_reg_type == PTR_TO_CTX ||
1883 insn->imm == PTR_TO_CTX)) {
1884 verbose("same insn cannot be used with different pointers\n");
1885 return -EINVAL;
1886 }
1887
1888 } else if (class == BPF_ST) {
1889 if (BPF_MODE(insn->code) != BPF_MEM ||
1890 insn->src_reg != BPF_REG_0) {
1891 verbose("BPF_ST uses reserved fields\n");
1892 return -EINVAL;
1893 }
1894 /* check src operand */
1895 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1896 if (err)
1897 return err;
1898
1899 /* check that memory (dst_reg + off) is writeable */
1900 err = check_mem_access(env, insn->dst_reg, insn->off,
1901 BPF_SIZE(insn->code), BPF_WRITE,
1902 -1);
1903 if (err)
1904 return err;
1905
1906 } else if (class == BPF_JMP) {
1907 u8 opcode = BPF_OP(insn->code);
1908
1909 if (opcode == BPF_CALL) {
1910 if (BPF_SRC(insn->code) != BPF_K ||
1911 insn->off != 0 ||
1912 insn->src_reg != BPF_REG_0 ||
1913 insn->dst_reg != BPF_REG_0) {
1914 verbose("BPF_CALL uses reserved fields\n");
1915 return -EINVAL;
1916 }
1917
1918 err = check_call(env, insn->imm);
1919 if (err)
1920 return err;
1921
1922 } else if (opcode == BPF_JA) {
1923 if (BPF_SRC(insn->code) != BPF_K ||
1924 insn->imm != 0 ||
1925 insn->src_reg != BPF_REG_0 ||
1926 insn->dst_reg != BPF_REG_0) {
1927 verbose("BPF_JA uses reserved fields\n");
1928 return -EINVAL;
1929 }
1930
1931 insn_idx += insn->off + 1;
1932 continue;
1933
1934 } else if (opcode == BPF_EXIT) {
1935 if (BPF_SRC(insn->code) != BPF_K ||
1936 insn->imm != 0 ||
1937 insn->src_reg != BPF_REG_0 ||
1938 insn->dst_reg != BPF_REG_0) {
1939 verbose("BPF_EXIT uses reserved fields\n");
1940 return -EINVAL;
1941 }
1942
1943 /* eBPF calling convetion is such that R0 is used
1944 * to return the value from eBPF program.
1945 * Make sure that it's readable at this time
1946 * of bpf_exit, which means that program wrote
1947 * something into it earlier
1948 */
1949 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1950 if (err)
1951 return err;
1952
1953 if (is_pointer_value(env, BPF_REG_0)) {
1954 verbose("R0 leaks addr as return value\n");
1955 return -EACCES;
1956 }
1957
1958process_bpf_exit:
1959 insn_idx = pop_stack(env, &prev_insn_idx);
1960 if (insn_idx < 0) {
1961 break;
1962 } else {
1963 do_print_state = true;
1964 continue;
1965 }
1966 } else {
1967 err = check_cond_jmp_op(env, insn, &insn_idx);
1968 if (err)
1969 return err;
1970 }
1971 } else if (class == BPF_LD) {
1972 u8 mode = BPF_MODE(insn->code);
1973
1974 if (mode == BPF_ABS || mode == BPF_IND) {
1975 err = check_ld_abs(env, insn);
1976 if (err)
1977 return err;
1978
1979 } else if (mode == BPF_IMM) {
1980 err = check_ld_imm(env, insn);
1981 if (err)
1982 return err;
1983
1984 insn_idx++;
1985 } else {
1986 verbose("invalid BPF_LD mode\n");
1987 return -EINVAL;
1988 }
1989 } else {
1990 verbose("unknown insn class %d\n", class);
1991 return -EINVAL;
1992 }
1993
1994 insn_idx++;
1995 }
1996
1997 return 0;
1998}
1999
2000/* look for pseudo eBPF instructions that access map FDs and
2001 * replace them with actual map pointers
2002 */
2003static int replace_map_fd_with_map_ptr(struct verifier_env *env)
2004{
2005 struct bpf_insn *insn = env->prog->insnsi;
2006 int insn_cnt = env->prog->len;
2007 int i, j;
2008
2009 for (i = 0; i < insn_cnt; i++, insn++) {
2010 if (BPF_CLASS(insn->code) == BPF_LDX &&
2011 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
2012 verbose("BPF_LDX uses reserved fields\n");
2013 return -EINVAL;
2014 }
2015
2016 if (BPF_CLASS(insn->code) == BPF_STX &&
2017 ((BPF_MODE(insn->code) != BPF_MEM &&
2018 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2019 verbose("BPF_STX uses reserved fields\n");
2020 return -EINVAL;
2021 }
2022
2023 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2024 struct bpf_map *map;
2025 struct fd f;
2026
2027 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2028 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2029 insn[1].off != 0) {
2030 verbose("invalid bpf_ld_imm64 insn\n");
2031 return -EINVAL;
2032 }
2033
2034 if (insn->src_reg == 0)
2035 /* valid generic load 64-bit imm */
2036 goto next_insn;
2037
2038 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2039 verbose("unrecognized bpf_ld_imm64 insn\n");
2040 return -EINVAL;
2041 }
2042
2043 f = fdget(insn->imm);
2044 map = __bpf_map_get(f);
2045 if (IS_ERR(map)) {
2046 verbose("fd %d is not pointing to valid bpf_map\n",
2047 insn->imm);
2048 return PTR_ERR(map);
2049 }
2050
2051 /* store map pointer inside BPF_LD_IMM64 instruction */
2052 insn[0].imm = (u32) (unsigned long) map;
2053 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2054
2055 /* check whether we recorded this map already */
2056 for (j = 0; j < env->used_map_cnt; j++)
2057 if (env->used_maps[j] == map) {
2058 fdput(f);
2059 goto next_insn;
2060 }
2061
2062 if (env->used_map_cnt >= MAX_USED_MAPS) {
2063 fdput(f);
2064 return -E2BIG;
2065 }
2066
2067 /* hold the map. If the program is rejected by verifier,
2068 * the map will be released by release_maps() or it
2069 * will be used by the valid program until it's unloaded
2070 * and all maps are released in free_bpf_prog_info()
2071 */
2072 map = bpf_map_inc(map, false);
2073 if (IS_ERR(map)) {
2074 fdput(f);
2075 return PTR_ERR(map);
2076 }
2077 env->used_maps[env->used_map_cnt++] = map;
2078
2079 fdput(f);
2080next_insn:
2081 insn++;
2082 i++;
2083 }
2084 }
2085
2086 /* now all pseudo BPF_LD_IMM64 instructions load valid
2087 * 'struct bpf_map *' into a register instead of user map_fd.
2088 * These pointers will be used later by verifier to validate map access.
2089 */
2090 return 0;
2091}
2092
2093/* drop refcnt of maps used by the rejected program */
2094static void release_maps(struct verifier_env *env)
2095{
2096 int i;
2097
2098 for (i = 0; i < env->used_map_cnt; i++)
2099 bpf_map_put(env->used_maps[i]);
2100}
2101
2102/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2103static void convert_pseudo_ld_imm64(struct verifier_env *env)
2104{
2105 struct bpf_insn *insn = env->prog->insnsi;
2106 int insn_cnt = env->prog->len;
2107 int i;
2108
2109 for (i = 0; i < insn_cnt; i++, insn++)
2110 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2111 insn->src_reg = 0;
2112}
2113
2114static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
2115{
2116 struct bpf_insn *insn = prog->insnsi;
2117 int insn_cnt = prog->len;
2118 int i;
2119
2120 for (i = 0; i < insn_cnt; i++, insn++) {
2121 if (BPF_CLASS(insn->code) != BPF_JMP ||
2122 BPF_OP(insn->code) == BPF_CALL ||
2123 BPF_OP(insn->code) == BPF_EXIT)
2124 continue;
2125
2126 /* adjust offset of jmps if necessary */
2127 if (i < pos && i + insn->off + 1 > pos)
2128 insn->off += delta;
2129 else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
2130 insn->off -= delta;
2131 }
2132}
2133
2134/* convert load instructions that access fields of 'struct __sk_buff'
2135 * into sequence of instructions that access fields of 'struct sk_buff'
2136 */
2137static int convert_ctx_accesses(struct verifier_env *env)
2138{
2139 struct bpf_insn *insn = env->prog->insnsi;
2140 int insn_cnt = env->prog->len;
2141 struct bpf_insn insn_buf[16];
2142 struct bpf_prog *new_prog;
2143 u32 cnt;
2144 int i;
2145 enum bpf_access_type type;
2146
2147 if (!env->prog->aux->ops->convert_ctx_access)
2148 return 0;
2149
2150 for (i = 0; i < insn_cnt; i++, insn++) {
2151 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2152 type = BPF_READ;
2153 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2154 type = BPF_WRITE;
2155 else
2156 continue;
2157
2158 if (insn->imm != PTR_TO_CTX) {
2159 /* clear internal mark */
2160 insn->imm = 0;
2161 continue;
2162 }
2163
2164 cnt = env->prog->aux->ops->
2165 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
2166 insn->off, insn_buf, env->prog);
2167 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2168 verbose("bpf verifier is misconfigured\n");
2169 return -EINVAL;
2170 }
2171
2172 if (cnt == 1) {
2173 memcpy(insn, insn_buf, sizeof(*insn));
2174 continue;
2175 }
2176
2177 /* several new insns need to be inserted. Make room for them */
2178 insn_cnt += cnt - 1;
2179 new_prog = bpf_prog_realloc(env->prog,
2180 bpf_prog_size(insn_cnt),
2181 GFP_USER);
2182 if (!new_prog)
2183 return -ENOMEM;
2184
2185 new_prog->len = insn_cnt;
2186
2187 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2188 sizeof(*insn) * (insn_cnt - i - cnt));
2189
2190 /* copy substitute insns in place of load instruction */
2191 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2192
2193 /* adjust branches in the whole program */
2194 adjust_branches(new_prog, i, cnt - 1);
2195
2196 /* keep walking new program and skip insns we just inserted */
2197 env->prog = new_prog;
2198 insn = new_prog->insnsi + i + cnt - 1;
2199 i += cnt - 1;
2200 }
2201
2202 return 0;
2203}
2204
2205static void free_states(struct verifier_env *env)
2206{
2207 struct verifier_state_list *sl, *sln;
2208 int i;
2209
2210 if (!env->explored_states)
2211 return;
2212
2213 for (i = 0; i < env->prog->len; i++) {
2214 sl = env->explored_states[i];
2215
2216 if (sl)
2217 while (sl != STATE_LIST_MARK) {
2218 sln = sl->next;
2219 kfree(sl);
2220 sl = sln;
2221 }
2222 }
2223
2224 kfree(env->explored_states);
2225}
2226
2227int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
2228{
2229 char __user *log_ubuf = NULL;
2230 struct verifier_env *env;
2231 int ret = -EINVAL;
2232
2233 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
2234 return -E2BIG;
2235
2236 /* 'struct verifier_env' can be global, but since it's not small,
2237 * allocate/free it every time bpf_check() is called
2238 */
2239 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2240 if (!env)
2241 return -ENOMEM;
2242
2243 env->prog = *prog;
2244
2245 /* grab the mutex to protect few globals used by verifier */
2246 mutex_lock(&bpf_verifier_lock);
2247
2248 if (attr->log_level || attr->log_buf || attr->log_size) {
2249 /* user requested verbose verifier output
2250 * and supplied buffer to store the verification trace
2251 */
2252 log_level = attr->log_level;
2253 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2254 log_size = attr->log_size;
2255 log_len = 0;
2256
2257 ret = -EINVAL;
2258 /* log_* values have to be sane */
2259 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2260 log_level == 0 || log_ubuf == NULL)
2261 goto free_env;
2262
2263 ret = -ENOMEM;
2264 log_buf = vmalloc(log_size);
2265 if (!log_buf)
2266 goto free_env;
2267 } else {
2268 log_level = 0;
2269 }
2270
2271 ret = replace_map_fd_with_map_ptr(env);
2272 if (ret < 0)
2273 goto skip_full_check;
2274
2275 env->explored_states = kcalloc(env->prog->len,
2276 sizeof(struct verifier_state_list *),
2277 GFP_USER);
2278 ret = -ENOMEM;
2279 if (!env->explored_states)
2280 goto skip_full_check;
2281
2282 ret = check_cfg(env);
2283 if (ret < 0)
2284 goto skip_full_check;
2285
2286 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2287
2288 ret = do_check(env);
2289
2290skip_full_check:
2291 while (pop_stack(env, NULL) >= 0);
2292 free_states(env);
2293
2294 if (ret == 0)
2295 /* program is valid, convert *(u32*)(ctx + off) accesses */
2296 ret = convert_ctx_accesses(env);
2297
2298 if (log_level && log_len >= log_size - 1) {
2299 BUG_ON(log_len >= log_size);
2300 /* verifier log exceeded user supplied buffer */
2301 ret = -ENOSPC;
2302 /* fall through to return what was recorded */
2303 }
2304
2305 /* copy verifier log back to user space including trailing zero */
2306 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2307 ret = -EFAULT;
2308 goto free_log_buf;
2309 }
2310
2311 if (ret == 0 && env->used_map_cnt) {
2312 /* if program passed verifier, update used_maps in bpf_prog_info */
2313 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2314 sizeof(env->used_maps[0]),
2315 GFP_KERNEL);
2316
2317 if (!env->prog->aux->used_maps) {
2318 ret = -ENOMEM;
2319 goto free_log_buf;
2320 }
2321
2322 memcpy(env->prog->aux->used_maps, env->used_maps,
2323 sizeof(env->used_maps[0]) * env->used_map_cnt);
2324 env->prog->aux->used_map_cnt = env->used_map_cnt;
2325
2326 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2327 * bpf_ld_imm64 instructions
2328 */
2329 convert_pseudo_ld_imm64(env);
2330 }
2331
2332free_log_buf:
2333 if (log_level)
2334 vfree(log_buf);
2335free_env:
2336 if (!env->prog->aux->used_maps)
2337 /* if we didn't copy map pointers into bpf_prog_info, release
2338 * them now. Otherwise free_bpf_prog_info() will release them.
2339 */
2340 release_maps(env);
2341 *prog = env->prog;
2342 kfree(env);
2343 mutex_unlock(&bpf_verifier_lock);
2344 return ret;
2345}