1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 * Copyright (c) 2016 Facebook
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of version 2 of the GNU General Public
6 * License as published by the Free Software Foundation.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 #include <linux/kernel.h>
14 #include <linux/types.h>
15 #include <linux/slab.h>
16 #include <linux/bpf.h>
17 #include <linux/filter.h>
18 #include <net/netlink.h>
19 #include <linux/file.h>
20 #include <linux/vmalloc.h>
22 /* bpf_check() is a static code analyzer that walks eBPF program
23 * instruction by instruction and updates register/stack state.
24 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
26 * The first pass is depth-first-search to check that the program is a DAG.
27 * It rejects the following programs:
28 * - larger than BPF_MAXINSNS insns
29 * - if loop is present (detected via back-edge)
30 * - unreachable insns exist (shouldn't be a forest. program = one function)
31 * - out of bounds or malformed jumps
32 * The second pass is all possible path descent from the 1st insn.
33 * Since it's analyzing all pathes through the program, the length of the
34 * analysis is limited to 32k insn, which may be hit even if total number of
35 * insn is less then 4K, but there are too many branches that change stack/regs.
36 * Number of 'branches to be analyzed' is limited to 1k
38 * On entry to each instruction, each register has a type, and the instruction
39 * changes the types of the registers depending on instruction semantics.
40 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
43 * All registers are 64-bit.
44 * R0 - return register
45 * R1-R5 argument passing registers
46 * R6-R9 callee saved registers
47 * R10 - frame pointer read-only
49 * At the start of BPF program the register R1 contains a pointer to bpf_context
50 * and has type PTR_TO_CTX.
52 * Verifier tracks arithmetic operations on pointers in case:
53 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
54 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
55 * 1st insn copies R10 (which has FRAME_PTR) type into R1
56 * and 2nd arithmetic instruction is pattern matched to recognize
57 * that it wants to construct a pointer to some element within stack.
58 * So after 2nd insn, the register R1 has type PTR_TO_STACK
59 * (and -20 constant is saved for further stack bounds checking).
60 * Meaning that this reg is a pointer to stack plus known immediate constant.
62 * Most of the time the registers have UNKNOWN_VALUE type, which
63 * means the register has some value, but it's not a valid pointer.
64 * (like pointer plus pointer becomes UNKNOWN_VALUE type)
66 * When verifier sees load or store instructions the type of base register
67 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
68 * types recognized by check_mem_access() function.
70 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
71 * and the range of [ptr, ptr + map's value_size) is accessible.
73 * registers used to pass values to function calls are checked against
74 * function argument constraints.
76 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
77 * It means that the register type passed to this function must be
78 * PTR_TO_STACK and it will be used inside the function as
79 * 'pointer to map element key'
81 * For example the argument constraints for bpf_map_lookup_elem():
82 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
83 * .arg1_type = ARG_CONST_MAP_PTR,
84 * .arg2_type = ARG_PTR_TO_MAP_KEY,
86 * ret_type says that this function returns 'pointer to map elem value or null'
87 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
88 * 2nd argument should be a pointer to stack, which will be used inside
89 * the helper function as a pointer to map element key.
91 * On the kernel side the helper function looks like:
92 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
94 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
95 * void *key = (void *) (unsigned long) r2;
98 * here kernel can access 'key' and 'map' pointers safely, knowing that
99 * [key, key + map->key_size) bytes are valid and were initialized on
100 * the stack of eBPF program.
103 * Corresponding eBPF program may look like:
104 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
105 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
106 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
107 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
108 * here verifier looks at prototype of map_lookup_elem() and sees:
109 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
110 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
112 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
113 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
114 * and were initialized prior to this call.
115 * If it's ok, then verifier allows this BPF_CALL insn and looks at
116 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
117 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
118 * returns ether pointer to map value or NULL.
120 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
121 * insn, the register holding that pointer in the true branch changes state to
122 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
123 * branch. See check_cond_jmp_op().
125 * After the call R0 is set to return type of the function and registers R1-R5
126 * are set to NOT_INIT to indicate that they are no longer readable.
130 enum bpf_reg_type type;
132 /* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */
135 /* valid when type == PTR_TO_PACKET* */
142 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
143 * PTR_TO_MAP_VALUE_OR_NULL
145 struct bpf_map *map_ptr;
149 enum bpf_stack_slot_type {
150 STACK_INVALID, /* nothing was stored in this stack slot */
151 STACK_SPILL, /* register spilled into stack */
152 STACK_MISC /* BPF program wrote some data into this slot */
155 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
157 /* state of the program:
158 * type of all registers and stack info
160 struct verifier_state {
161 struct reg_state regs[MAX_BPF_REG];
162 u8 stack_slot_type[MAX_BPF_STACK];
163 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
166 /* linked list of verifier states used to prune search */
167 struct verifier_state_list {
168 struct verifier_state state;
169 struct verifier_state_list *next;
172 /* verifier_state + insn_idx are pushed to stack when branch is encountered */
173 struct verifier_stack_elem {
174 /* verifer state is 'st'
175 * before processing instruction 'insn_idx'
176 * and after processing instruction 'prev_insn_idx'
178 struct verifier_state st;
181 struct verifier_stack_elem *next;
184 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
186 /* single container for all structs
187 * one verifier_env per bpf_check() call
189 struct verifier_env {
190 struct bpf_prog *prog; /* eBPF program being verified */
191 struct verifier_stack_elem *head; /* stack of verifier states to be processed */
192 int stack_size; /* number of states to be processed */
193 struct verifier_state cur_state; /* current verifier state */
194 struct verifier_state_list **explored_states; /* search pruning optimization */
195 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
196 u32 used_map_cnt; /* number of used maps */
197 bool allow_ptr_leaks;
200 #define BPF_COMPLEXITY_LIMIT_INSNS 65536
201 #define BPF_COMPLEXITY_LIMIT_STACK 1024
203 struct bpf_call_arg_meta {
204 struct bpf_map *map_ptr;
210 /* verbose verifier prints what it's seeing
211 * bpf_check() is called under lock, so no race to access these global vars
213 static u32 log_level, log_size, log_len;
214 static char *log_buf;
216 static DEFINE_MUTEX(bpf_verifier_lock);
218 /* log_level controls verbosity level of eBPF verifier.
219 * verbose() is used to dump the verification trace to the log, so the user
220 * can figure out what's wrong with the program
222 static __printf(1, 2) void verbose(const char *fmt, ...)
226 if (log_level == 0 || log_len >= log_size - 1)
230 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
234 /* string representation of 'enum bpf_reg_type' */
235 static const char * const reg_type_str[] = {
237 [UNKNOWN_VALUE] = "inv",
238 [PTR_TO_CTX] = "ctx",
239 [CONST_PTR_TO_MAP] = "map_ptr",
240 [PTR_TO_MAP_VALUE] = "map_value",
241 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
243 [PTR_TO_STACK] = "fp",
245 [PTR_TO_PACKET] = "pkt",
246 [PTR_TO_PACKET_END] = "pkt_end",
249 static void print_verifier_state(struct verifier_state *state)
251 struct reg_state *reg;
255 for (i = 0; i < MAX_BPF_REG; i++) {
256 reg = &state->regs[i];
260 verbose(" R%d=%s", i, reg_type_str[t]);
261 if (t == CONST_IMM || t == PTR_TO_STACK)
262 verbose("%lld", reg->imm);
263 else if (t == PTR_TO_PACKET)
264 verbose("(id=%d,off=%d,r=%d)",
265 reg->id, reg->off, reg->range);
266 else if (t == UNKNOWN_VALUE && reg->imm)
267 verbose("%lld", reg->imm);
268 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
269 t == PTR_TO_MAP_VALUE_OR_NULL)
270 verbose("(ks=%d,vs=%d)",
271 reg->map_ptr->key_size,
272 reg->map_ptr->value_size);
274 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
275 if (state->stack_slot_type[i] == STACK_SPILL)
276 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
277 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]);
282 static const char *const bpf_class_string[] = {
290 [BPF_ALU64] = "alu64",
293 static const char *const bpf_alu_string[16] = {
294 [BPF_ADD >> 4] = "+=",
295 [BPF_SUB >> 4] = "-=",
296 [BPF_MUL >> 4] = "*=",
297 [BPF_DIV >> 4] = "/=",
298 [BPF_OR >> 4] = "|=",
299 [BPF_AND >> 4] = "&=",
300 [BPF_LSH >> 4] = "<<=",
301 [BPF_RSH >> 4] = ">>=",
302 [BPF_NEG >> 4] = "neg",
303 [BPF_MOD >> 4] = "%=",
304 [BPF_XOR >> 4] = "^=",
305 [BPF_MOV >> 4] = "=",
306 [BPF_ARSH >> 4] = "s>>=",
307 [BPF_END >> 4] = "endian",
310 static const char *const bpf_ldst_string[] = {
311 [BPF_W >> 3] = "u32",
312 [BPF_H >> 3] = "u16",
314 [BPF_DW >> 3] = "u64",
317 static const char *const bpf_jmp_string[16] = {
318 [BPF_JA >> 4] = "jmp",
319 [BPF_JEQ >> 4] = "==",
320 [BPF_JGT >> 4] = ">",
321 [BPF_JGE >> 4] = ">=",
322 [BPF_JSET >> 4] = "&",
323 [BPF_JNE >> 4] = "!=",
324 [BPF_JSGT >> 4] = "s>",
325 [BPF_JSGE >> 4] = "s>=",
326 [BPF_CALL >> 4] = "call",
327 [BPF_EXIT >> 4] = "exit",
330 static void print_bpf_insn(struct bpf_insn *insn)
332 u8 class = BPF_CLASS(insn->code);
334 if (class == BPF_ALU || class == BPF_ALU64) {
335 if (BPF_SRC(insn->code) == BPF_X)
336 verbose("(%02x) %sr%d %s %sr%d\n",
337 insn->code, class == BPF_ALU ? "(u32) " : "",
339 bpf_alu_string[BPF_OP(insn->code) >> 4],
340 class == BPF_ALU ? "(u32) " : "",
343 verbose("(%02x) %sr%d %s %s%d\n",
344 insn->code, class == BPF_ALU ? "(u32) " : "",
346 bpf_alu_string[BPF_OP(insn->code) >> 4],
347 class == BPF_ALU ? "(u32) " : "",
349 } else if (class == BPF_STX) {
350 if (BPF_MODE(insn->code) == BPF_MEM)
351 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
353 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
355 insn->off, insn->src_reg);
356 else if (BPF_MODE(insn->code) == BPF_XADD)
357 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
359 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
360 insn->dst_reg, insn->off,
363 verbose("BUG_%02x\n", insn->code);
364 } else if (class == BPF_ST) {
365 if (BPF_MODE(insn->code) != BPF_MEM) {
366 verbose("BUG_st_%02x\n", insn->code);
369 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
371 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
373 insn->off, insn->imm);
374 } else if (class == BPF_LDX) {
375 if (BPF_MODE(insn->code) != BPF_MEM) {
376 verbose("BUG_ldx_%02x\n", insn->code);
379 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
380 insn->code, insn->dst_reg,
381 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
382 insn->src_reg, insn->off);
383 } else if (class == BPF_LD) {
384 if (BPF_MODE(insn->code) == BPF_ABS) {
385 verbose("(%02x) r0 = *(%s *)skb[%d]\n",
387 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
389 } else if (BPF_MODE(insn->code) == BPF_IND) {
390 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
392 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
393 insn->src_reg, insn->imm);
394 } else if (BPF_MODE(insn->code) == BPF_IMM) {
395 verbose("(%02x) r%d = 0x%x\n",
396 insn->code, insn->dst_reg, insn->imm);
398 verbose("BUG_ld_%02x\n", insn->code);
401 } else if (class == BPF_JMP) {
402 u8 opcode = BPF_OP(insn->code);
404 if (opcode == BPF_CALL) {
405 verbose("(%02x) call %d\n", insn->code, insn->imm);
406 } else if (insn->code == (BPF_JMP | BPF_JA)) {
407 verbose("(%02x) goto pc%+d\n",
408 insn->code, insn->off);
409 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
410 verbose("(%02x) exit\n", insn->code);
411 } else if (BPF_SRC(insn->code) == BPF_X) {
412 verbose("(%02x) if r%d %s r%d goto pc%+d\n",
413 insn->code, insn->dst_reg,
414 bpf_jmp_string[BPF_OP(insn->code) >> 4],
415 insn->src_reg, insn->off);
417 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
418 insn->code, insn->dst_reg,
419 bpf_jmp_string[BPF_OP(insn->code) >> 4],
420 insn->imm, insn->off);
423 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
427 static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
429 struct verifier_stack_elem *elem;
432 if (env->head == NULL)
435 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
436 insn_idx = env->head->insn_idx;
438 *prev_insn_idx = env->head->prev_insn_idx;
439 elem = env->head->next;
446 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
449 struct verifier_stack_elem *elem;
451 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
455 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
456 elem->insn_idx = insn_idx;
457 elem->prev_insn_idx = prev_insn_idx;
458 elem->next = env->head;
461 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
462 verbose("BPF program is too complex\n");
467 /* pop all elements and return */
468 while (pop_stack(env, NULL) >= 0);
472 #define CALLER_SAVED_REGS 6
473 static const int caller_saved[CALLER_SAVED_REGS] = {
474 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
477 static void init_reg_state(struct reg_state *regs)
481 for (i = 0; i < MAX_BPF_REG; i++) {
482 regs[i].type = NOT_INIT;
487 regs[BPF_REG_FP].type = FRAME_PTR;
489 /* 1st arg to a function */
490 regs[BPF_REG_1].type = PTR_TO_CTX;
493 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
495 BUG_ON(regno >= MAX_BPF_REG);
496 regs[regno].type = UNKNOWN_VALUE;
501 SRC_OP, /* register is used as source operand */
502 DST_OP, /* register is used as destination operand */
503 DST_OP_NO_MARK /* same as above, check only, don't mark */
506 static int check_reg_arg(struct reg_state *regs, u32 regno,
509 if (regno >= MAX_BPF_REG) {
510 verbose("R%d is invalid\n", regno);
515 /* check whether register used as source operand can be read */
516 if (regs[regno].type == NOT_INIT) {
517 verbose("R%d !read_ok\n", regno);
521 /* check whether register used as dest operand can be written to */
522 if (regno == BPF_REG_FP) {
523 verbose("frame pointer is read only\n");
527 mark_reg_unknown_value(regs, regno);
532 static int bpf_size_to_bytes(int bpf_size)
534 if (bpf_size == BPF_W)
536 else if (bpf_size == BPF_H)
538 else if (bpf_size == BPF_B)
540 else if (bpf_size == BPF_DW)
546 static bool is_spillable_regtype(enum bpf_reg_type type)
549 case PTR_TO_MAP_VALUE:
550 case PTR_TO_MAP_VALUE_OR_NULL:
554 case PTR_TO_PACKET_END:
556 case CONST_PTR_TO_MAP:
563 /* check_stack_read/write functions track spill/fill of registers,
564 * stack boundary and alignment are checked in check_mem_access()
566 static int check_stack_write(struct verifier_state *state, int off, int size,
570 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
571 * so it's aligned access and [off, off + size) are within stack limits
574 if (value_regno >= 0 &&
575 is_spillable_regtype(state->regs[value_regno].type)) {
577 /* register containing pointer is being spilled into stack */
578 if (size != BPF_REG_SIZE) {
579 verbose("invalid size of register spill\n");
583 /* save register state */
584 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
585 state->regs[value_regno];
587 for (i = 0; i < BPF_REG_SIZE; i++)
588 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
590 /* regular write of data into stack */
591 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
592 (struct reg_state) {};
594 for (i = 0; i < size; i++)
595 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
600 static int check_stack_read(struct verifier_state *state, int off, int size,
606 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
608 if (slot_type[0] == STACK_SPILL) {
609 if (size != BPF_REG_SIZE) {
610 verbose("invalid size of register spill\n");
613 for (i = 1; i < BPF_REG_SIZE; i++) {
614 if (slot_type[i] != STACK_SPILL) {
615 verbose("corrupted spill memory\n");
620 if (value_regno >= 0)
621 /* restore register state from stack */
622 state->regs[value_regno] =
623 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
626 for (i = 0; i < size; i++) {
627 if (slot_type[i] != STACK_MISC) {
628 verbose("invalid read from stack off %d+%d size %d\n",
633 if (value_regno >= 0)
634 /* have read misc data from the stack */
635 mark_reg_unknown_value(state->regs, value_regno);
640 /* check read/write into map element returned by bpf_map_lookup_elem() */
641 static int check_map_access(struct verifier_env *env, u32 regno, int off,
644 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
646 if (off < 0 || off + size > map->value_size) {
647 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
648 map->value_size, off, size);
654 #define MAX_PACKET_OFF 0xffff
656 static int check_packet_access(struct verifier_env *env, u32 regno, int off,
659 struct reg_state *regs = env->cur_state.regs;
660 struct reg_state *reg = ®s[regno];
663 if (off < 0 || off + size > reg->range) {
664 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
665 off, size, regno, reg->id, reg->off, reg->range);
671 /* check access to 'struct bpf_context' fields */
672 static int check_ctx_access(struct verifier_env *env, int off, int size,
673 enum bpf_access_type t, enum bpf_reg_type *reg_type)
675 if (env->prog->aux->ops->is_valid_access &&
676 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) {
677 /* remember the offset of last byte accessed in ctx */
678 if (env->prog->aux->max_ctx_offset < off + size)
679 env->prog->aux->max_ctx_offset = off + size;
683 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
687 static bool is_pointer_value(struct verifier_env *env, int regno)
689 if (env->allow_ptr_leaks)
692 switch (env->cur_state.regs[regno].type) {
701 static int check_ptr_alignment(struct verifier_env *env, struct reg_state *reg,
704 if (reg->type != PTR_TO_PACKET) {
705 if (off % size != 0) {
706 verbose("misaligned access off %d size %d\n", off, size);
713 switch (env->prog->type) {
714 case BPF_PROG_TYPE_SCHED_CLS:
715 case BPF_PROG_TYPE_SCHED_ACT:
718 verbose("verifier is misconfigured\n");
722 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
723 /* misaligned access to packet is ok on x86,arm,arm64 */
726 if (reg->id && size != 1) {
727 verbose("Unknown packet alignment. Only byte-sized access allowed\n");
731 /* skb->data is NET_IP_ALIGN-ed */
732 if ((NET_IP_ALIGN + reg->off + off) % size != 0) {
733 verbose("misaligned packet access off %d+%d+%d size %d\n",
734 NET_IP_ALIGN, reg->off, off, size);
740 /* check whether memory at (regno + off) is accessible for t = (read | write)
741 * if t==write, value_regno is a register which value is stored into memory
742 * if t==read, value_regno is a register which will receive the value from memory
743 * if t==write && value_regno==-1, some unknown value is stored into memory
744 * if t==read && value_regno==-1, don't care what we read from memory
746 static int check_mem_access(struct verifier_env *env, u32 regno, int off,
747 int bpf_size, enum bpf_access_type t,
750 struct verifier_state *state = &env->cur_state;
751 struct reg_state *reg = &state->regs[regno];
754 if (reg->type == PTR_TO_STACK)
757 size = bpf_size_to_bytes(bpf_size);
761 err = check_ptr_alignment(env, reg, off, size);
765 if (reg->type == PTR_TO_MAP_VALUE) {
766 if (t == BPF_WRITE && value_regno >= 0 &&
767 is_pointer_value(env, value_regno)) {
768 verbose("R%d leaks addr into map\n", value_regno);
771 err = check_map_access(env, regno, off, size);
772 if (!err && t == BPF_READ && value_regno >= 0)
773 mark_reg_unknown_value(state->regs, value_regno);
775 } else if (reg->type == PTR_TO_CTX) {
776 enum bpf_reg_type reg_type = UNKNOWN_VALUE;
778 if (t == BPF_WRITE && value_regno >= 0 &&
779 is_pointer_value(env, value_regno)) {
780 verbose("R%d leaks addr into ctx\n", value_regno);
783 err = check_ctx_access(env, off, size, t, ®_type);
784 if (!err && t == BPF_READ && value_regno >= 0) {
785 mark_reg_unknown_value(state->regs, value_regno);
786 if (env->allow_ptr_leaks)
787 /* note that reg.[id|off|range] == 0 */
788 state->regs[value_regno].type = reg_type;
791 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {
792 if (off >= 0 || off < -MAX_BPF_STACK) {
793 verbose("invalid stack off=%d size=%d\n", off, size);
796 if (t == BPF_WRITE) {
797 if (!env->allow_ptr_leaks &&
798 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
799 size != BPF_REG_SIZE) {
800 verbose("attempt to corrupt spilled pointer on stack\n");
803 err = check_stack_write(state, off, size, value_regno);
805 err = check_stack_read(state, off, size, value_regno);
807 } else if (state->regs[regno].type == PTR_TO_PACKET) {
808 if (t == BPF_WRITE) {
809 verbose("cannot write into packet\n");
812 err = check_packet_access(env, regno, off, size);
813 if (!err && t == BPF_READ && value_regno >= 0)
814 mark_reg_unknown_value(state->regs, value_regno);
816 verbose("R%d invalid mem access '%s'\n",
817 regno, reg_type_str[reg->type]);
821 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks &&
822 state->regs[value_regno].type == UNKNOWN_VALUE) {
823 /* 1 or 2 byte load zero-extends, determine the number of
824 * zero upper bits. Not doing it fo 4 byte load, since
825 * such values cannot be added to ptr_to_packet anyway.
827 state->regs[value_regno].imm = 64 - size * 8;
832 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
834 struct reg_state *regs = env->cur_state.regs;
837 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
839 verbose("BPF_XADD uses reserved fields\n");
843 /* check src1 operand */
844 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
848 /* check src2 operand */
849 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
853 /* check whether atomic_add can read the memory */
854 err = check_mem_access(env, insn->dst_reg, insn->off,
855 BPF_SIZE(insn->code), BPF_READ, -1);
859 /* check whether atomic_add can write into the same memory */
860 return check_mem_access(env, insn->dst_reg, insn->off,
861 BPF_SIZE(insn->code), BPF_WRITE, -1);
864 /* when register 'regno' is passed into function that will read 'access_size'
865 * bytes from that pointer, make sure that it's within stack boundary
866 * and all elements of stack are initialized
868 static int check_stack_boundary(struct verifier_env *env, int regno,
869 int access_size, bool zero_size_allowed,
870 struct bpf_call_arg_meta *meta)
872 struct verifier_state *state = &env->cur_state;
873 struct reg_state *regs = state->regs;
876 if (regs[regno].type != PTR_TO_STACK) {
877 if (zero_size_allowed && access_size == 0 &&
878 regs[regno].type == CONST_IMM &&
879 regs[regno].imm == 0)
882 verbose("R%d type=%s expected=%s\n", regno,
883 reg_type_str[regs[regno].type],
884 reg_type_str[PTR_TO_STACK]);
888 off = regs[regno].imm;
889 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
891 verbose("invalid stack type R%d off=%d access_size=%d\n",
892 regno, off, access_size);
896 if (meta && meta->raw_mode) {
897 meta->access_size = access_size;
902 for (i = 0; i < access_size; i++) {
903 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
904 verbose("invalid indirect read from stack off %d+%d size %d\n",
905 off, i, access_size);
912 static int check_func_arg(struct verifier_env *env, u32 regno,
913 enum bpf_arg_type arg_type,
914 struct bpf_call_arg_meta *meta)
916 struct reg_state *reg = env->cur_state.regs + regno;
917 enum bpf_reg_type expected_type;
920 if (arg_type == ARG_DONTCARE)
923 if (reg->type == NOT_INIT) {
924 verbose("R%d !read_ok\n", regno);
928 if (arg_type == ARG_ANYTHING) {
929 if (is_pointer_value(env, regno)) {
930 verbose("R%d leaks addr into helper function\n", regno);
936 if (arg_type == ARG_PTR_TO_MAP_KEY ||
937 arg_type == ARG_PTR_TO_MAP_VALUE) {
938 expected_type = PTR_TO_STACK;
939 } else if (arg_type == ARG_CONST_STACK_SIZE ||
940 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
941 expected_type = CONST_IMM;
942 } else if (arg_type == ARG_CONST_MAP_PTR) {
943 expected_type = CONST_PTR_TO_MAP;
944 } else if (arg_type == ARG_PTR_TO_CTX) {
945 expected_type = PTR_TO_CTX;
946 } else if (arg_type == ARG_PTR_TO_STACK ||
947 arg_type == ARG_PTR_TO_RAW_STACK) {
948 expected_type = PTR_TO_STACK;
949 /* One exception here. In case function allows for NULL to be
950 * passed in as argument, it's a CONST_IMM type. Final test
951 * happens during stack boundary checking.
953 if (reg->type == CONST_IMM && reg->imm == 0)
954 expected_type = CONST_IMM;
955 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK;
957 verbose("unsupported arg_type %d\n", arg_type);
961 if (reg->type != expected_type) {
962 verbose("R%d type=%s expected=%s\n", regno,
963 reg_type_str[reg->type], reg_type_str[expected_type]);
967 if (arg_type == ARG_CONST_MAP_PTR) {
968 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
969 meta->map_ptr = reg->map_ptr;
970 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
971 /* bpf_map_xxx(..., map_ptr, ..., key) call:
972 * check that [key, key + map->key_size) are within
973 * stack limits and initialized
975 if (!meta->map_ptr) {
976 /* in function declaration map_ptr must come before
977 * map_key, so that it's verified and known before
978 * we have to check map_key here. Otherwise it means
979 * that kernel subsystem misconfigured verifier
981 verbose("invalid map_ptr to access map->key\n");
984 err = check_stack_boundary(env, regno, meta->map_ptr->key_size,
986 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
987 /* bpf_map_xxx(..., map_ptr, ..., value) call:
988 * check [value, value + map->value_size) validity
990 if (!meta->map_ptr) {
991 /* kernel subsystem misconfigured verifier */
992 verbose("invalid map_ptr to access map->value\n");
995 err = check_stack_boundary(env, regno,
996 meta->map_ptr->value_size,
998 } else if (arg_type == ARG_CONST_STACK_SIZE ||
999 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
1000 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
1002 /* bpf_xxx(..., buf, len) call will access 'len' bytes
1003 * from stack pointer 'buf'. Check it
1004 * note: regno == len, regno - 1 == buf
1007 /* kernel subsystem misconfigured verifier */
1008 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
1011 err = check_stack_boundary(env, regno - 1, reg->imm,
1012 zero_size_allowed, meta);
1018 static int check_map_func_compatibility(struct bpf_map *map, int func_id)
1023 /* We need a two way check, first is from map perspective ... */
1024 switch (map->map_type) {
1025 case BPF_MAP_TYPE_PROG_ARRAY:
1026 if (func_id != BPF_FUNC_tail_call)
1029 case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
1030 if (func_id != BPF_FUNC_perf_event_read &&
1031 func_id != BPF_FUNC_perf_event_output)
1034 case BPF_MAP_TYPE_STACK_TRACE:
1035 if (func_id != BPF_FUNC_get_stackid)
1042 /* ... and second from the function itself. */
1044 case BPF_FUNC_tail_call:
1045 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
1048 case BPF_FUNC_perf_event_read:
1049 case BPF_FUNC_perf_event_output:
1050 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
1053 case BPF_FUNC_get_stackid:
1054 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
1063 verbose("cannot pass map_type %d into func %d\n",
1064 map->map_type, func_id);
1068 static int check_raw_mode(const struct bpf_func_proto *fn)
1072 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK)
1074 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK)
1076 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK)
1078 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK)
1080 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK)
1083 return count > 1 ? -EINVAL : 0;
1086 static void clear_all_pkt_pointers(struct verifier_env *env)
1088 struct verifier_state *state = &env->cur_state;
1089 struct reg_state *regs = state->regs, *reg;
1092 for (i = 0; i < MAX_BPF_REG; i++)
1093 if (regs[i].type == PTR_TO_PACKET ||
1094 regs[i].type == PTR_TO_PACKET_END)
1095 mark_reg_unknown_value(regs, i);
1097 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1098 if (state->stack_slot_type[i] != STACK_SPILL)
1100 reg = &state->spilled_regs[i / BPF_REG_SIZE];
1101 if (reg->type != PTR_TO_PACKET &&
1102 reg->type != PTR_TO_PACKET_END)
1104 reg->type = UNKNOWN_VALUE;
1109 static int check_call(struct verifier_env *env, int func_id)
1111 struct verifier_state *state = &env->cur_state;
1112 const struct bpf_func_proto *fn = NULL;
1113 struct reg_state *regs = state->regs;
1114 struct reg_state *reg;
1115 struct bpf_call_arg_meta meta;
1119 /* find function prototype */
1120 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
1121 verbose("invalid func %d\n", func_id);
1125 if (env->prog->aux->ops->get_func_proto)
1126 fn = env->prog->aux->ops->get_func_proto(func_id);
1129 verbose("unknown func %d\n", func_id);
1133 /* eBPF programs must be GPL compatible to use GPL-ed functions */
1134 if (!env->prog->gpl_compatible && fn->gpl_only) {
1135 verbose("cannot call GPL only function from proprietary program\n");
1139 changes_data = bpf_helper_changes_skb_data(fn->func);
1141 memset(&meta, 0, sizeof(meta));
1143 /* We only support one arg being in raw mode at the moment, which
1144 * is sufficient for the helper functions we have right now.
1146 err = check_raw_mode(fn);
1148 verbose("kernel subsystem misconfigured func %d\n", func_id);
1153 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
1156 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
1159 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
1162 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
1165 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
1169 /* Mark slots with STACK_MISC in case of raw mode, stack offset
1170 * is inferred from register state.
1172 for (i = 0; i < meta.access_size; i++) {
1173 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1);
1178 /* reset caller saved regs */
1179 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1180 reg = regs + caller_saved[i];
1181 reg->type = NOT_INIT;
1185 /* update return register */
1186 if (fn->ret_type == RET_INTEGER) {
1187 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1188 } else if (fn->ret_type == RET_VOID) {
1189 regs[BPF_REG_0].type = NOT_INIT;
1190 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
1191 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
1192 /* remember map_ptr, so that check_map_access()
1193 * can check 'value_size' boundary of memory access
1194 * to map element returned from bpf_map_lookup_elem()
1196 if (meta.map_ptr == NULL) {
1197 verbose("kernel subsystem misconfigured verifier\n");
1200 regs[BPF_REG_0].map_ptr = meta.map_ptr;
1202 verbose("unknown return type %d of func %d\n",
1203 fn->ret_type, func_id);
1207 err = check_map_func_compatibility(meta.map_ptr, func_id);
1212 clear_all_pkt_pointers(env);
1216 static int check_packet_ptr_add(struct verifier_env *env, struct bpf_insn *insn)
1218 struct reg_state *regs = env->cur_state.regs;
1219 struct reg_state *dst_reg = ®s[insn->dst_reg];
1220 struct reg_state *src_reg = ®s[insn->src_reg];
1221 struct reg_state tmp_reg;
1224 if (BPF_SRC(insn->code) == BPF_K) {
1225 /* pkt_ptr += imm */
1230 verbose("addition of negative constant to packet pointer is not allowed\n");
1233 if (imm >= MAX_PACKET_OFF ||
1234 imm + dst_reg->off >= MAX_PACKET_OFF) {
1235 verbose("constant %d is too large to add to packet pointer\n",
1239 /* a constant was added to pkt_ptr.
1240 * Remember it while keeping the same 'id'
1242 dst_reg->off += imm;
1244 if (src_reg->type == PTR_TO_PACKET) {
1245 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */
1246 tmp_reg = *dst_reg; /* save r7 state */
1247 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */
1248 src_reg = &tmp_reg; /* pretend it's src_reg state */
1249 /* if the checks below reject it, the copy won't matter,
1250 * since we're rejecting the whole program. If all ok,
1251 * then imm22 state will be added to r7
1252 * and r7 will be pkt(id=0,off=22,r=62) while
1253 * r6 will stay as pkt(id=0,off=0,r=62)
1257 if (src_reg->type == CONST_IMM) {
1258 /* pkt_ptr += reg where reg is known constant */
1262 /* disallow pkt_ptr += reg
1263 * if reg is not uknown_value with guaranteed zero upper bits
1264 * otherwise pkt_ptr may overflow and addition will become
1265 * subtraction which is not allowed
1267 if (src_reg->type != UNKNOWN_VALUE) {
1268 verbose("cannot add '%s' to ptr_to_packet\n",
1269 reg_type_str[src_reg->type]);
1272 if (src_reg->imm < 48) {
1273 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n",
1277 /* dst_reg stays as pkt_ptr type and since some positive
1278 * integer value was added to the pointer, increment its 'id'
1282 /* something was added to pkt_ptr, set range and off to zero */
1289 static int evaluate_reg_alu(struct verifier_env *env, struct bpf_insn *insn)
1291 struct reg_state *regs = env->cur_state.regs;
1292 struct reg_state *dst_reg = ®s[insn->dst_reg];
1293 u8 opcode = BPF_OP(insn->code);
1296 /* for type == UNKNOWN_VALUE:
1297 * imm > 0 -> number of zero upper bits
1298 * imm == 0 -> don't track which is the same as all bits can be non-zero
1301 if (BPF_SRC(insn->code) == BPF_X) {
1302 struct reg_state *src_reg = ®s[insn->src_reg];
1304 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 &&
1305 dst_reg->imm && opcode == BPF_ADD) {
1307 * where both have zero upper bits. Adding them
1308 * can only result making one more bit non-zero
1309 * in the larger value.
1310 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47)
1311 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47)
1313 dst_reg->imm = min(dst_reg->imm, src_reg->imm);
1317 if (src_reg->type == CONST_IMM && src_reg->imm > 0 &&
1318 dst_reg->imm && opcode == BPF_ADD) {
1320 * where dreg has zero upper bits and sreg is const.
1321 * Adding them can only result making one more bit
1322 * non-zero in the larger value.
1324 imm_log2 = __ilog2_u64((long long)src_reg->imm);
1325 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
1329 /* all other cases non supported yet, just mark dst_reg */
1334 /* sign extend 32-bit imm into 64-bit to make sure that
1335 * negative values occupy bit 63. Note ilog2() would have
1336 * been incorrect, since sizeof(insn->imm) == 4
1338 imm_log2 = __ilog2_u64((long long)insn->imm);
1340 if (dst_reg->imm && opcode == BPF_LSH) {
1342 * if reg was a result of 2 byte load, then its imm == 48
1343 * which means that upper 48 bits are zero and shifting this reg
1344 * left by 4 would mean that upper 44 bits are still zero
1346 dst_reg->imm -= insn->imm;
1347 } else if (dst_reg->imm && opcode == BPF_MUL) {
1349 * if multiplying by 14 subtract 4
1350 * This is conservative calculation of upper zero bits.
1351 * It's not trying to special case insn->imm == 1 or 0 cases
1353 dst_reg->imm -= imm_log2 + 1;
1354 } else if (opcode == BPF_AND) {
1356 dst_reg->imm = 63 - imm_log2;
1357 } else if (dst_reg->imm && opcode == BPF_ADD) {
1359 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
1361 } else if (opcode == BPF_RSH) {
1363 * which means that after right shift, upper bits will be zero
1364 * note that verifier already checked that
1365 * 0 <= imm < 64 for shift insn
1367 dst_reg->imm += insn->imm;
1368 if (unlikely(dst_reg->imm > 64))
1369 /* some dumb code did:
1372 * and all bits are zero now */
1375 /* all other alu ops, means that we don't know what will
1376 * happen to the value, mark it with unknown number of zero bits
1381 if (dst_reg->imm < 0) {
1382 /* all 64 bits of the register can contain non-zero bits
1383 * and such value cannot be added to ptr_to_packet, since it
1384 * may overflow, mark it as unknown to avoid further eval
1391 static int evaluate_reg_imm_alu(struct verifier_env *env, struct bpf_insn *insn)
1393 struct reg_state *regs = env->cur_state.regs;
1394 struct reg_state *dst_reg = ®s[insn->dst_reg];
1395 struct reg_state *src_reg = ®s[insn->src_reg];
1396 u8 opcode = BPF_OP(insn->code);
1398 /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn.
1399 * Don't care about overflow or negative values, just add them
1401 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K)
1402 dst_reg->imm += insn->imm;
1403 else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X &&
1404 src_reg->type == CONST_IMM)
1405 dst_reg->imm += src_reg->imm;
1407 mark_reg_unknown_value(regs, insn->dst_reg);
1411 /* check validity of 32-bit and 64-bit arithmetic operations */
1412 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn)
1414 struct reg_state *regs = env->cur_state.regs, *dst_reg;
1415 u8 opcode = BPF_OP(insn->code);
1418 if (opcode == BPF_END || opcode == BPF_NEG) {
1419 if (opcode == BPF_NEG) {
1420 if (BPF_SRC(insn->code) != 0 ||
1421 insn->src_reg != BPF_REG_0 ||
1422 insn->off != 0 || insn->imm != 0) {
1423 verbose("BPF_NEG uses reserved fields\n");
1427 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1428 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1429 verbose("BPF_END uses reserved fields\n");
1434 /* check src operand */
1435 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1439 if (is_pointer_value(env, insn->dst_reg)) {
1440 verbose("R%d pointer arithmetic prohibited\n",
1445 /* check dest operand */
1446 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1450 } else if (opcode == BPF_MOV) {
1452 if (BPF_SRC(insn->code) == BPF_X) {
1453 if (insn->imm != 0 || insn->off != 0) {
1454 verbose("BPF_MOV uses reserved fields\n");
1458 /* check src operand */
1459 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1463 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1464 verbose("BPF_MOV uses reserved fields\n");
1469 /* check dest operand */
1470 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1474 if (BPF_SRC(insn->code) == BPF_X) {
1475 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1477 * copy register state to dest reg
1479 regs[insn->dst_reg] = regs[insn->src_reg];
1481 if (is_pointer_value(env, insn->src_reg)) {
1482 verbose("R%d partial copy of pointer\n",
1486 regs[insn->dst_reg].type = UNKNOWN_VALUE;
1487 regs[insn->dst_reg].map_ptr = NULL;
1491 * remember the value we stored into this reg
1493 regs[insn->dst_reg].type = CONST_IMM;
1494 regs[insn->dst_reg].imm = insn->imm;
1497 } else if (opcode > BPF_END) {
1498 verbose("invalid BPF_ALU opcode %x\n", opcode);
1501 } else { /* all other ALU ops: and, sub, xor, add, ... */
1503 if (BPF_SRC(insn->code) == BPF_X) {
1504 if (insn->imm != 0 || insn->off != 0) {
1505 verbose("BPF_ALU uses reserved fields\n");
1508 /* check src1 operand */
1509 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1513 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1514 verbose("BPF_ALU uses reserved fields\n");
1519 /* check src2 operand */
1520 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1524 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1525 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1526 verbose("div by zero\n");
1530 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1531 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1532 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1534 if (insn->imm < 0 || insn->imm >= size) {
1535 verbose("invalid shift %d\n", insn->imm);
1540 /* check dest operand */
1541 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1545 dst_reg = ®s[insn->dst_reg];
1547 /* pattern match 'bpf_add Rx, imm' instruction */
1548 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1549 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) {
1550 dst_reg->type = PTR_TO_STACK;
1551 dst_reg->imm = insn->imm;
1553 } else if (opcode == BPF_ADD &&
1554 BPF_CLASS(insn->code) == BPF_ALU64 &&
1555 (dst_reg->type == PTR_TO_PACKET ||
1556 (BPF_SRC(insn->code) == BPF_X &&
1557 regs[insn->src_reg].type == PTR_TO_PACKET))) {
1558 /* ptr_to_packet += K|X */
1559 return check_packet_ptr_add(env, insn);
1560 } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
1561 dst_reg->type == UNKNOWN_VALUE &&
1562 env->allow_ptr_leaks) {
1563 /* unknown += K|X */
1564 return evaluate_reg_alu(env, insn);
1565 } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
1566 dst_reg->type == CONST_IMM &&
1567 env->allow_ptr_leaks) {
1568 /* reg_imm += K|X */
1569 return evaluate_reg_imm_alu(env, insn);
1570 } else if (is_pointer_value(env, insn->dst_reg)) {
1571 verbose("R%d pointer arithmetic prohibited\n",
1574 } else if (BPF_SRC(insn->code) == BPF_X &&
1575 is_pointer_value(env, insn->src_reg)) {
1576 verbose("R%d pointer arithmetic prohibited\n",
1581 /* mark dest operand */
1582 mark_reg_unknown_value(regs, insn->dst_reg);
1588 static void find_good_pkt_pointers(struct verifier_env *env,
1589 struct reg_state *dst_reg)
1591 struct verifier_state *state = &env->cur_state;
1592 struct reg_state *regs = state->regs, *reg;
1596 * if (r2 > pkt_end) goto somewhere
1597 * r2 == dst_reg, pkt_end == src_reg,
1598 * r2=pkt(id=n,off=8,r=0)
1599 * r3=pkt(id=n,off=0,r=0)
1600 * find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
1601 * so that range of bytes [r3, r3 + 8) is safe to access
1603 for (i = 0; i < MAX_BPF_REG; i++)
1604 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
1605 regs[i].range = dst_reg->off;
1607 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
1608 if (state->stack_slot_type[i] != STACK_SPILL)
1610 reg = &state->spilled_regs[i / BPF_REG_SIZE];
1611 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
1612 reg->range = dst_reg->off;
1616 static int check_cond_jmp_op(struct verifier_env *env,
1617 struct bpf_insn *insn, int *insn_idx)
1619 struct reg_state *regs = env->cur_state.regs, *dst_reg;
1620 struct verifier_state *other_branch;
1621 u8 opcode = BPF_OP(insn->code);
1624 if (opcode > BPF_EXIT) {
1625 verbose("invalid BPF_JMP opcode %x\n", opcode);
1629 if (BPF_SRC(insn->code) == BPF_X) {
1630 if (insn->imm != 0) {
1631 verbose("BPF_JMP uses reserved fields\n");
1635 /* check src1 operand */
1636 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1640 if (is_pointer_value(env, insn->src_reg)) {
1641 verbose("R%d pointer comparison prohibited\n",
1646 if (insn->src_reg != BPF_REG_0) {
1647 verbose("BPF_JMP uses reserved fields\n");
1652 /* check src2 operand */
1653 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1657 dst_reg = ®s[insn->dst_reg];
1659 /* detect if R == 0 where R was initialized to zero earlier */
1660 if (BPF_SRC(insn->code) == BPF_K &&
1661 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1662 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) {
1663 if (opcode == BPF_JEQ) {
1664 /* if (imm == imm) goto pc+off;
1665 * only follow the goto, ignore fall-through
1667 *insn_idx += insn->off;
1670 /* if (imm != imm) goto pc+off;
1671 * only follow fall-through branch, since
1672 * that's where the program will go
1678 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1682 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1683 if (BPF_SRC(insn->code) == BPF_K &&
1684 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1685 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
1686 if (opcode == BPF_JEQ) {
1687 /* next fallthrough insn can access memory via
1690 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1691 /* branch targer cannot access it, since reg == 0 */
1692 mark_reg_unknown_value(other_branch->regs,
1695 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1696 mark_reg_unknown_value(regs, insn->dst_reg);
1698 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
1699 dst_reg->type == PTR_TO_PACKET &&
1700 regs[insn->src_reg].type == PTR_TO_PACKET_END) {
1701 find_good_pkt_pointers(env, dst_reg);
1702 } else if (is_pointer_value(env, insn->dst_reg)) {
1703 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
1707 print_verifier_state(&env->cur_state);
1711 /* return the map pointer stored inside BPF_LD_IMM64 instruction */
1712 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1714 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1716 return (struct bpf_map *) (unsigned long) imm64;
1719 /* verify BPF_LD_IMM64 instruction */
1720 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1722 struct reg_state *regs = env->cur_state.regs;
1725 if (BPF_SIZE(insn->code) != BPF_DW) {
1726 verbose("invalid BPF_LD_IMM insn\n");
1729 if (insn->off != 0) {
1730 verbose("BPF_LD_IMM64 uses reserved fields\n");
1734 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1738 if (insn->src_reg == 0)
1739 /* generic move 64-bit immediate into a register */
1742 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1743 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1745 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1746 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1750 static bool may_access_skb(enum bpf_prog_type type)
1753 case BPF_PROG_TYPE_SOCKET_FILTER:
1754 case BPF_PROG_TYPE_SCHED_CLS:
1755 case BPF_PROG_TYPE_SCHED_ACT:
1762 /* verify safety of LD_ABS|LD_IND instructions:
1763 * - they can only appear in the programs where ctx == skb
1764 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1765 * preserve R6-R9, and store return value into R0
1768 * ctx == skb == R6 == CTX
1771 * SRC == any register
1772 * IMM == 32-bit immediate
1775 * R0 - 8/16/32-bit skb data converted to cpu endianness
1777 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1779 struct reg_state *regs = env->cur_state.regs;
1780 u8 mode = BPF_MODE(insn->code);
1781 struct reg_state *reg;
1784 if (!may_access_skb(env->prog->type)) {
1785 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
1789 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1790 BPF_SIZE(insn->code) == BPF_DW ||
1791 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1792 verbose("BPF_LD_[ABS|IND] uses reserved fields\n");
1796 /* check whether implicit source operand (register R6) is readable */
1797 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1801 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1802 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1806 if (mode == BPF_IND) {
1807 /* check explicit source operand */
1808 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1813 /* reset caller saved regs to unreadable */
1814 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1815 reg = regs + caller_saved[i];
1816 reg->type = NOT_INIT;
1820 /* mark destination R0 register as readable, since it contains
1821 * the value fetched from the packet
1823 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1827 /* non-recursive DFS pseudo code
1828 * 1 procedure DFS-iterative(G,v):
1829 * 2 label v as discovered
1830 * 3 let S be a stack
1832 * 5 while S is not empty
1834 * 7 if t is what we're looking for:
1836 * 9 for all edges e in G.adjacentEdges(t) do
1837 * 10 if edge e is already labelled
1838 * 11 continue with the next edge
1839 * 12 w <- G.adjacentVertex(t,e)
1840 * 13 if vertex w is not discovered and not explored
1841 * 14 label e as tree-edge
1842 * 15 label w as discovered
1845 * 18 else if vertex w is discovered
1846 * 19 label e as back-edge
1848 * 21 // vertex w is explored
1849 * 22 label e as forward- or cross-edge
1850 * 23 label t as explored
1855 * 0x11 - discovered and fall-through edge labelled
1856 * 0x12 - discovered and fall-through and branch edges labelled
1867 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1869 static int *insn_stack; /* stack of insns to process */
1870 static int cur_stack; /* current stack index */
1871 static int *insn_state;
1873 /* t, w, e - match pseudo-code above:
1874 * t - index of current instruction
1875 * w - next instruction
1878 static int push_insn(int t, int w, int e, struct verifier_env *env)
1880 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1883 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1886 if (w < 0 || w >= env->prog->len) {
1887 verbose("jump out of range from insn %d to %d\n", t, w);
1892 /* mark branch target for state pruning */
1893 env->explored_states[w] = STATE_LIST_MARK;
1895 if (insn_state[w] == 0) {
1897 insn_state[t] = DISCOVERED | e;
1898 insn_state[w] = DISCOVERED;
1899 if (cur_stack >= env->prog->len)
1901 insn_stack[cur_stack++] = w;
1903 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1904 verbose("back-edge from insn %d to %d\n", t, w);
1906 } else if (insn_state[w] == EXPLORED) {
1907 /* forward- or cross-edge */
1908 insn_state[t] = DISCOVERED | e;
1910 verbose("insn state internal bug\n");
1916 /* non-recursive depth-first-search to detect loops in BPF program
1917 * loop == back-edge in directed graph
1919 static int check_cfg(struct verifier_env *env)
1921 struct bpf_insn *insns = env->prog->insnsi;
1922 int insn_cnt = env->prog->len;
1926 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1930 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1936 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1937 insn_stack[0] = 0; /* 0 is the first instruction */
1943 t = insn_stack[cur_stack - 1];
1945 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1946 u8 opcode = BPF_OP(insns[t].code);
1948 if (opcode == BPF_EXIT) {
1950 } else if (opcode == BPF_CALL) {
1951 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1956 if (t + 1 < insn_cnt)
1957 env->explored_states[t + 1] = STATE_LIST_MARK;
1958 } else if (opcode == BPF_JA) {
1959 if (BPF_SRC(insns[t].code) != BPF_K) {
1963 /* unconditional jump with single edge */
1964 ret = push_insn(t, t + insns[t].off + 1,
1970 /* tell verifier to check for equivalent states
1971 * after every call and jump
1973 if (t + 1 < insn_cnt)
1974 env->explored_states[t + 1] = STATE_LIST_MARK;
1976 /* conditional jump with two edges */
1977 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1983 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1990 /* all other non-branch instructions with single
1993 ret = push_insn(t, t + 1, FALLTHROUGH, env);
2001 insn_state[t] = EXPLORED;
2002 if (cur_stack-- <= 0) {
2003 verbose("pop stack internal bug\n");
2010 for (i = 0; i < insn_cnt; i++) {
2011 if (insn_state[i] != EXPLORED) {
2012 verbose("unreachable insn %d\n", i);
2017 ret = 0; /* cfg looks good */
2025 /* the following conditions reduce the number of explored insns
2026 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet
2028 static bool compare_ptrs_to_packet(struct reg_state *old, struct reg_state *cur)
2030 if (old->id != cur->id)
2033 /* old ptr_to_packet is more conservative, since it allows smaller
2035 * old(off=0,r=10) is equal to cur(off=0,r=20), because
2036 * old(off=0,r=10) means that with range=10 the verifier proceeded
2037 * further and found no issues with the program. Now we're in the same
2038 * spot with cur(off=0,r=20), so we're safe too, since anything further
2039 * will only be looking at most 10 bytes after this pointer.
2041 if (old->off == cur->off && old->range < cur->range)
2044 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0)
2045 * since both cannot be used for packet access and safe(old)
2046 * pointer has smaller off that could be used for further
2047 * 'if (ptr > data_end)' check
2049 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean
2050 * that we cannot access the packet.
2051 * The safe range is:
2052 * [ptr, ptr + range - off)
2053 * so whenever off >=range, it means no safe bytes from this pointer.
2054 * When comparing old->off <= cur->off, it means that older code
2055 * went with smaller offset and that offset was later
2056 * used to figure out the safe range after 'if (ptr > data_end)' check
2057 * Say, 'old' state was explored like:
2058 * ... R3(off=0, r=0)
2060 * ... now R4(off=20,r=0) <-- here
2061 * if (R4 > data_end)
2062 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access.
2063 * ... the code further went all the way to bpf_exit.
2064 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0).
2065 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier
2066 * goes further, such cur_R4 will give larger safe packet range after
2067 * 'if (R4 > data_end)' and all further insn were already good with r=20,
2068 * so they will be good with r=30 and we can prune the search.
2070 if (old->off <= cur->off &&
2071 old->off >= old->range && cur->off >= cur->range)
2077 /* compare two verifier states
2079 * all states stored in state_list are known to be valid, since
2080 * verifier reached 'bpf_exit' instruction through them
2082 * this function is called when verifier exploring different branches of
2083 * execution popped from the state stack. If it sees an old state that has
2084 * more strict register state and more strict stack state then this execution
2085 * branch doesn't need to be explored further, since verifier already
2086 * concluded that more strict state leads to valid finish.
2088 * Therefore two states are equivalent if register state is more conservative
2089 * and explored stack state is more conservative than the current one.
2092 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
2093 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
2095 * In other words if current stack state (one being explored) has more
2096 * valid slots than old one that already passed validation, it means
2097 * the verifier can stop exploring and conclude that current state is valid too
2099 * Similarly with registers. If explored state has register type as invalid
2100 * whereas register type in current state is meaningful, it means that
2101 * the current state will reach 'bpf_exit' instruction safely
2103 static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
2105 struct reg_state *rold, *rcur;
2108 for (i = 0; i < MAX_BPF_REG; i++) {
2109 rold = &old->regs[i];
2110 rcur = &cur->regs[i];
2112 if (memcmp(rold, rcur, sizeof(*rold)) == 0)
2115 if (rold->type == NOT_INIT ||
2116 (rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT))
2119 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET &&
2120 compare_ptrs_to_packet(rold, rcur))
2126 for (i = 0; i < MAX_BPF_STACK; i++) {
2127 if (old->stack_slot_type[i] == STACK_INVALID)
2129 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
2130 /* Ex: old explored (safe) state has STACK_SPILL in
2131 * this stack slot, but current has has STACK_MISC ->
2132 * this verifier states are not equivalent,
2133 * return false to continue verification of this path
2136 if (i % BPF_REG_SIZE)
2138 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
2139 &cur->spilled_regs[i / BPF_REG_SIZE],
2140 sizeof(old->spilled_regs[0])))
2141 /* when explored and current stack slot types are
2142 * the same, check that stored pointers types
2143 * are the same as well.
2144 * Ex: explored safe path could have stored
2145 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
2146 * but current path has stored:
2147 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
2148 * such verifier states are not equivalent.
2149 * return false to continue verification of this path
2158 static int is_state_visited(struct verifier_env *env, int insn_idx)
2160 struct verifier_state_list *new_sl;
2161 struct verifier_state_list *sl;
2163 sl = env->explored_states[insn_idx];
2165 /* this 'insn_idx' instruction wasn't marked, so we will not
2166 * be doing state search here
2170 while (sl != STATE_LIST_MARK) {
2171 if (states_equal(&sl->state, &env->cur_state))
2172 /* reached equivalent register/stack state,
2179 /* there were no equivalent states, remember current one.
2180 * technically the current state is not proven to be safe yet,
2181 * but it will either reach bpf_exit (which means it's safe) or
2182 * it will be rejected. Since there are no loops, we won't be
2183 * seeing this 'insn_idx' instruction again on the way to bpf_exit
2185 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
2189 /* add new state to the head of linked list */
2190 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
2191 new_sl->next = env->explored_states[insn_idx];
2192 env->explored_states[insn_idx] = new_sl;
2196 static int do_check(struct verifier_env *env)
2198 struct verifier_state *state = &env->cur_state;
2199 struct bpf_insn *insns = env->prog->insnsi;
2200 struct reg_state *regs = state->regs;
2201 int insn_cnt = env->prog->len;
2202 int insn_idx, prev_insn_idx = 0;
2203 int insn_processed = 0;
2204 bool do_print_state = false;
2206 init_reg_state(regs);
2209 struct bpf_insn *insn;
2213 if (insn_idx >= insn_cnt) {
2214 verbose("invalid insn idx %d insn_cnt %d\n",
2215 insn_idx, insn_cnt);
2219 insn = &insns[insn_idx];
2220 class = BPF_CLASS(insn->code);
2222 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
2223 verbose("BPF program is too large. Proccessed %d insn\n",
2228 err = is_state_visited(env, insn_idx);
2232 /* found equivalent state, can prune the search */
2235 verbose("\nfrom %d to %d: safe\n",
2236 prev_insn_idx, insn_idx);
2238 verbose("%d: safe\n", insn_idx);
2240 goto process_bpf_exit;
2243 if (log_level && do_print_state) {
2244 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
2245 print_verifier_state(&env->cur_state);
2246 do_print_state = false;
2250 verbose("%d: ", insn_idx);
2251 print_bpf_insn(insn);
2254 if (class == BPF_ALU || class == BPF_ALU64) {
2255 err = check_alu_op(env, insn);
2259 } else if (class == BPF_LDX) {
2260 enum bpf_reg_type src_reg_type;
2262 /* check for reserved fields is already done */
2264 /* check src operand */
2265 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2269 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
2273 src_reg_type = regs[insn->src_reg].type;
2275 /* check that memory (src_reg + off) is readable,
2276 * the state of dst_reg will be updated by this func
2278 err = check_mem_access(env, insn->src_reg, insn->off,
2279 BPF_SIZE(insn->code), BPF_READ,
2284 if (BPF_SIZE(insn->code) != BPF_W) {
2289 if (insn->imm == 0) {
2291 * dst_reg = *(u32 *)(src_reg + off)
2292 * use reserved 'imm' field to mark this insn
2294 insn->imm = src_reg_type;
2296 } else if (src_reg_type != insn->imm &&
2297 (src_reg_type == PTR_TO_CTX ||
2298 insn->imm == PTR_TO_CTX)) {
2299 /* ABuser program is trying to use the same insn
2300 * dst_reg = *(u32*) (src_reg + off)
2301 * with different pointer types:
2302 * src_reg == ctx in one branch and
2303 * src_reg == stack|map in some other branch.
2306 verbose("same insn cannot be used with different pointers\n");
2310 } else if (class == BPF_STX) {
2311 enum bpf_reg_type dst_reg_type;
2313 if (BPF_MODE(insn->code) == BPF_XADD) {
2314 err = check_xadd(env, insn);
2321 /* check src1 operand */
2322 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
2325 /* check src2 operand */
2326 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2330 dst_reg_type = regs[insn->dst_reg].type;
2332 /* check that memory (dst_reg + off) is writeable */
2333 err = check_mem_access(env, insn->dst_reg, insn->off,
2334 BPF_SIZE(insn->code), BPF_WRITE,
2339 if (insn->imm == 0) {
2340 insn->imm = dst_reg_type;
2341 } else if (dst_reg_type != insn->imm &&
2342 (dst_reg_type == PTR_TO_CTX ||
2343 insn->imm == PTR_TO_CTX)) {
2344 verbose("same insn cannot be used with different pointers\n");
2348 } else if (class == BPF_ST) {
2349 if (BPF_MODE(insn->code) != BPF_MEM ||
2350 insn->src_reg != BPF_REG_0) {
2351 verbose("BPF_ST uses reserved fields\n");
2354 /* check src operand */
2355 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
2359 /* check that memory (dst_reg + off) is writeable */
2360 err = check_mem_access(env, insn->dst_reg, insn->off,
2361 BPF_SIZE(insn->code), BPF_WRITE,
2366 } else if (class == BPF_JMP) {
2367 u8 opcode = BPF_OP(insn->code);
2369 if (opcode == BPF_CALL) {
2370 if (BPF_SRC(insn->code) != BPF_K ||
2372 insn->src_reg != BPF_REG_0 ||
2373 insn->dst_reg != BPF_REG_0) {
2374 verbose("BPF_CALL uses reserved fields\n");
2378 err = check_call(env, insn->imm);
2382 } else if (opcode == BPF_JA) {
2383 if (BPF_SRC(insn->code) != BPF_K ||
2385 insn->src_reg != BPF_REG_0 ||
2386 insn->dst_reg != BPF_REG_0) {
2387 verbose("BPF_JA uses reserved fields\n");
2391 insn_idx += insn->off + 1;
2394 } else if (opcode == BPF_EXIT) {
2395 if (BPF_SRC(insn->code) != BPF_K ||
2397 insn->src_reg != BPF_REG_0 ||
2398 insn->dst_reg != BPF_REG_0) {
2399 verbose("BPF_EXIT uses reserved fields\n");
2403 /* eBPF calling convetion is such that R0 is used
2404 * to return the value from eBPF program.
2405 * Make sure that it's readable at this time
2406 * of bpf_exit, which means that program wrote
2407 * something into it earlier
2409 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
2413 if (is_pointer_value(env, BPF_REG_0)) {
2414 verbose("R0 leaks addr as return value\n");
2419 insn_idx = pop_stack(env, &prev_insn_idx);
2423 do_print_state = true;
2427 err = check_cond_jmp_op(env, insn, &insn_idx);
2431 } else if (class == BPF_LD) {
2432 u8 mode = BPF_MODE(insn->code);
2434 if (mode == BPF_ABS || mode == BPF_IND) {
2435 err = check_ld_abs(env, insn);
2439 } else if (mode == BPF_IMM) {
2440 err = check_ld_imm(env, insn);
2446 verbose("invalid BPF_LD mode\n");
2450 verbose("unknown insn class %d\n", class);
2457 verbose("processed %d insns\n", insn_processed);
2461 /* look for pseudo eBPF instructions that access map FDs and
2462 * replace them with actual map pointers
2464 static int replace_map_fd_with_map_ptr(struct verifier_env *env)
2466 struct bpf_insn *insn = env->prog->insnsi;
2467 int insn_cnt = env->prog->len;
2470 for (i = 0; i < insn_cnt; i++, insn++) {
2471 if (BPF_CLASS(insn->code) == BPF_LDX &&
2472 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
2473 verbose("BPF_LDX uses reserved fields\n");
2477 if (BPF_CLASS(insn->code) == BPF_STX &&
2478 ((BPF_MODE(insn->code) != BPF_MEM &&
2479 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2480 verbose("BPF_STX uses reserved fields\n");
2484 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2485 struct bpf_map *map;
2488 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2489 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2491 verbose("invalid bpf_ld_imm64 insn\n");
2495 if (insn->src_reg == 0)
2496 /* valid generic load 64-bit imm */
2499 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2500 verbose("unrecognized bpf_ld_imm64 insn\n");
2504 f = fdget(insn->imm);
2505 map = __bpf_map_get(f);
2507 verbose("fd %d is not pointing to valid bpf_map\n",
2509 return PTR_ERR(map);
2512 /* store map pointer inside BPF_LD_IMM64 instruction */
2513 insn[0].imm = (u32) (unsigned long) map;
2514 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2516 /* check whether we recorded this map already */
2517 for (j = 0; j < env->used_map_cnt; j++)
2518 if (env->used_maps[j] == map) {
2523 if (env->used_map_cnt >= MAX_USED_MAPS) {
2528 /* hold the map. If the program is rejected by verifier,
2529 * the map will be released by release_maps() or it
2530 * will be used by the valid program until it's unloaded
2531 * and all maps are released in free_bpf_prog_info()
2533 map = bpf_map_inc(map, false);
2536 return PTR_ERR(map);
2538 env->used_maps[env->used_map_cnt++] = map;
2547 /* now all pseudo BPF_LD_IMM64 instructions load valid
2548 * 'struct bpf_map *' into a register instead of user map_fd.
2549 * These pointers will be used later by verifier to validate map access.
2554 /* drop refcnt of maps used by the rejected program */
2555 static void release_maps(struct verifier_env *env)
2559 for (i = 0; i < env->used_map_cnt; i++)
2560 bpf_map_put(env->used_maps[i]);
2563 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2564 static void convert_pseudo_ld_imm64(struct verifier_env *env)
2566 struct bpf_insn *insn = env->prog->insnsi;
2567 int insn_cnt = env->prog->len;
2570 for (i = 0; i < insn_cnt; i++, insn++)
2571 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2575 /* convert load instructions that access fields of 'struct __sk_buff'
2576 * into sequence of instructions that access fields of 'struct sk_buff'
2578 static int convert_ctx_accesses(struct verifier_env *env)
2580 struct bpf_insn *insn = env->prog->insnsi;
2581 int insn_cnt = env->prog->len;
2582 struct bpf_insn insn_buf[16];
2583 struct bpf_prog *new_prog;
2584 enum bpf_access_type type;
2587 if (!env->prog->aux->ops->convert_ctx_access)
2590 for (i = 0; i < insn_cnt; i++, insn++) {
2591 u32 insn_delta, cnt;
2593 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2595 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2600 if (insn->imm != PTR_TO_CTX) {
2601 /* clear internal mark */
2606 cnt = env->prog->aux->ops->
2607 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
2608 insn->off, insn_buf, env->prog);
2609 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2610 verbose("bpf verifier is misconfigured\n");
2614 new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt);
2618 insn_delta = cnt - 1;
2620 /* keep walking new program and skip insns we just inserted */
2621 env->prog = new_prog;
2622 insn = new_prog->insnsi + i + insn_delta;
2624 insn_cnt += insn_delta;
2631 static void free_states(struct verifier_env *env)
2633 struct verifier_state_list *sl, *sln;
2636 if (!env->explored_states)
2639 for (i = 0; i < env->prog->len; i++) {
2640 sl = env->explored_states[i];
2643 while (sl != STATE_LIST_MARK) {
2650 kfree(env->explored_states);
2653 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
2655 char __user *log_ubuf = NULL;
2656 struct verifier_env *env;
2659 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
2662 /* 'struct verifier_env' can be global, but since it's not small,
2663 * allocate/free it every time bpf_check() is called
2665 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2671 /* grab the mutex to protect few globals used by verifier */
2672 mutex_lock(&bpf_verifier_lock);
2674 if (attr->log_level || attr->log_buf || attr->log_size) {
2675 /* user requested verbose verifier output
2676 * and supplied buffer to store the verification trace
2678 log_level = attr->log_level;
2679 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2680 log_size = attr->log_size;
2684 /* log_* values have to be sane */
2685 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2686 log_level == 0 || log_ubuf == NULL)
2690 log_buf = vmalloc(log_size);
2697 ret = replace_map_fd_with_map_ptr(env);
2699 goto skip_full_check;
2701 env->explored_states = kcalloc(env->prog->len,
2702 sizeof(struct verifier_state_list *),
2705 if (!env->explored_states)
2706 goto skip_full_check;
2708 ret = check_cfg(env);
2710 goto skip_full_check;
2712 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2714 ret = do_check(env);
2717 while (pop_stack(env, NULL) >= 0);
2721 /* program is valid, convert *(u32*)(ctx + off) accesses */
2722 ret = convert_ctx_accesses(env);
2724 if (log_level && log_len >= log_size - 1) {
2725 BUG_ON(log_len >= log_size);
2726 /* verifier log exceeded user supplied buffer */
2728 /* fall through to return what was recorded */
2731 /* copy verifier log back to user space including trailing zero */
2732 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2737 if (ret == 0 && env->used_map_cnt) {
2738 /* if program passed verifier, update used_maps in bpf_prog_info */
2739 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2740 sizeof(env->used_maps[0]),
2743 if (!env->prog->aux->used_maps) {
2748 memcpy(env->prog->aux->used_maps, env->used_maps,
2749 sizeof(env->used_maps[0]) * env->used_map_cnt);
2750 env->prog->aux->used_map_cnt = env->used_map_cnt;
2752 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2753 * bpf_ld_imm64 instructions
2755 convert_pseudo_ld_imm64(env);
2762 if (!env->prog->aux->used_maps)
2763 /* if we didn't copy map pointers into bpf_prog_info, release
2764 * them now. Otherwise free_bpf_prog_info() will release them.
2769 mutex_unlock(&bpf_verifier_lock);