1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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.
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.
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>
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.
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
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
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
48 * At the start of BPF program the register R1 contains a pointer to bpf_context
49 * and has type PTR_TO_CTX.
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.
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)
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.
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.
72 * registers used to pass values to function calls are checked against
73 * function argument constraints.
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'
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,
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.
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)
93 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
94 * void *key = (void *) (unsigned long) r2;
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.
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
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.
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().
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.
128 /* types of values stored in eBPF registers */
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 */
142 enum bpf_reg_type type;
144 /* valid when type == CONST_IMM | PTR_TO_STACK */
147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
148 * PTR_TO_MAP_VALUE_OR_NULL
150 struct bpf_map *map_ptr;
154 enum bpf_stack_slot_type {
155 STACK_INVALID, /* nothing was stored in this stack slot */
156 STACK_SPILL, /* register spilled into stack */
157 STACK_MISC /* BPF program wrote some data into this slot */
160 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
162 /* state of the program:
163 * type of all registers and stack info
165 struct verifier_state {
166 struct reg_state regs[MAX_BPF_REG];
167 u8 stack_slot_type[MAX_BPF_STACK];
168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
171 /* linked list of verifier states used to prune search */
172 struct verifier_state_list {
173 struct verifier_state state;
174 struct verifier_state_list *next;
177 /* verifier_state + insn_idx are pushed to stack when branch is encountered */
178 struct verifier_stack_elem {
179 /* verifer state is 'st'
180 * before processing instruction 'insn_idx'
181 * and after processing instruction 'prev_insn_idx'
183 struct verifier_state st;
186 struct verifier_stack_elem *next;
189 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
191 /* single container for all structs
192 * one verifier_env per bpf_check() call
194 struct verifier_env {
195 struct bpf_prog *prog; /* eBPF program being verified */
196 struct verifier_stack_elem *head; /* stack of verifier states to be processed */
197 int stack_size; /* number of states to be processed */
198 struct verifier_state cur_state; /* current verifier state */
199 struct verifier_state_list **explored_states; /* search pruning optimization */
200 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
201 u32 used_map_cnt; /* number of used maps */
202 bool allow_ptr_leaks;
205 /* verbose verifier prints what it's seeing
206 * bpf_check() is called under lock, so no race to access these global vars
208 static u32 log_level, log_size, log_len;
209 static char *log_buf;
211 static DEFINE_MUTEX(bpf_verifier_lock);
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
217 static __printf(1, 2) void verbose(const char *fmt, ...)
221 if (log_level == 0 || log_len >= log_size - 1)
225 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
229 /* string representation of 'enum bpf_reg_type' */
230 static const char * const reg_type_str[] = {
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",
238 [PTR_TO_STACK] = "fp",
242 static void print_verifier_state(struct verifier_env *env)
247 for (i = 0; i < MAX_BPF_REG; i++) {
248 t = env->cur_state.regs[i].type;
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);
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]);
268 static const char *const bpf_class_string[] = {
276 [BPF_ALU64] = "alu64",
279 static 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",
296 static const char *const bpf_ldst_string[] = {
297 [BPF_W >> 3] = "u32",
298 [BPF_H >> 3] = "u16",
300 [BPF_DW >> 3] = "u64",
303 static 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",
316 static void print_bpf_insn(struct bpf_insn *insn)
318 u8 class = BPF_CLASS(insn->code);
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) " : "",
325 bpf_alu_string[BPF_OP(insn->code) >> 4],
326 class == BPF_ALU ? "(u32) " : "",
329 verbose("(%02x) %sr%d %s %s%d\n",
330 insn->code, class == BPF_ALU ? "(u32) " : "",
332 bpf_alu_string[BPF_OP(insn->code) >> 4],
333 class == BPF_ALU ? "(u32) " : "",
335 } else if (class == BPF_STX) {
336 if (BPF_MODE(insn->code) == BPF_MEM)
337 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
339 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
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",
345 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
346 insn->dst_reg, insn->off,
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);
355 verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
357 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
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);
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",
373 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
375 } else if (BPF_MODE(insn->code) == BPF_IND) {
376 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
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);
384 verbose("BUG_ld_%02x\n", insn->code);
387 } else if (class == BPF_JMP) {
388 u8 opcode = BPF_OP(insn->code);
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);
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);
409 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
413 static int pop_stack(struct verifier_env *env, int *prev_insn_idx)
415 struct verifier_stack_elem *elem;
418 if (env->head == NULL)
421 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
422 insn_idx = env->head->insn_idx;
424 *prev_insn_idx = env->head->prev_insn_idx;
425 elem = env->head->next;
432 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx,
435 struct verifier_stack_elem *elem;
437 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL);
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;
447 if (env->stack_size > 1024) {
448 verbose("BPF program is too complex\n");
453 /* pop all elements and return */
454 while (pop_stack(env, NULL) >= 0);
458 #define CALLER_SAVED_REGS 6
459 static 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
463 static void init_reg_state(struct reg_state *regs)
467 for (i = 0; i < MAX_BPF_REG; i++) {
468 regs[i].type = NOT_INIT;
470 regs[i].map_ptr = NULL;
474 regs[BPF_REG_FP].type = FRAME_PTR;
476 /* 1st arg to a function */
477 regs[BPF_REG_1].type = PTR_TO_CTX;
480 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
482 BUG_ON(regno >= MAX_BPF_REG);
483 regs[regno].type = UNKNOWN_VALUE;
485 regs[regno].map_ptr = NULL;
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 */
494 static int check_reg_arg(struct reg_state *regs, u32 regno,
497 if (regno >= MAX_BPF_REG) {
498 verbose("R%d is invalid\n", regno);
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);
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");
515 mark_reg_unknown_value(regs, regno);
520 static int bpf_size_to_bytes(int bpf_size)
522 if (bpf_size == BPF_W)
524 else if (bpf_size == BPF_H)
526 else if (bpf_size == BPF_B)
528 else if (bpf_size == BPF_DW)
534 static bool is_spillable_regtype(enum bpf_reg_type type)
537 case PTR_TO_MAP_VALUE:
538 case PTR_TO_MAP_VALUE_OR_NULL:
542 case CONST_PTR_TO_MAP:
549 /* check_stack_read/write functions track spill/fill of registers,
550 * stack boundary and alignment are checked in check_mem_access()
552 static int check_stack_write(struct verifier_state *state, int off, int size,
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
560 if (value_regno >= 0 &&
561 is_spillable_regtype(state->regs[value_regno].type)) {
563 /* register containing pointer is being spilled into stack */
564 if (size != BPF_REG_SIZE) {
565 verbose("invalid size of register spill\n");
569 /* save register state */
570 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
571 state->regs[value_regno];
573 for (i = 0; i < BPF_REG_SIZE; i++)
574 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
576 /* regular write of data into stack */
577 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
578 (struct reg_state) {};
580 for (i = 0; i < size; i++)
581 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
586 static int check_stack_read(struct verifier_state *state, int off, int size,
592 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
594 if (slot_type[0] == STACK_SPILL) {
595 if (size != BPF_REG_SIZE) {
596 verbose("invalid size of register spill\n");
599 for (i = 1; i < BPF_REG_SIZE; i++) {
600 if (slot_type[i] != STACK_SPILL) {
601 verbose("corrupted spill memory\n");
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];
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",
619 if (value_regno >= 0)
620 /* have read misc data from the stack */
621 mark_reg_unknown_value(state->regs, value_regno);
626 /* check read/write into map element returned by bpf_map_lookup_elem() */
627 static int check_map_access(struct verifier_env *env, u32 regno, int off,
630 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
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);
640 /* check access to 'struct bpf_context' fields */
641 static int check_ctx_access(struct verifier_env *env, int off, int size,
642 enum bpf_access_type t)
644 if (env->prog->aux->ops->is_valid_access &&
645 env->prog->aux->ops->is_valid_access(off, size, t))
648 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
652 static bool is_pointer_value(struct verifier_env *env, int regno)
654 if (env->allow_ptr_leaks)
657 switch (env->cur_state.regs[regno].type) {
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
672 static int check_mem_access(struct verifier_env *env, u32 regno, int off,
673 int bpf_size, enum bpf_access_type t,
676 struct verifier_state *state = &env->cur_state;
679 if (state->regs[regno].type == PTR_TO_STACK)
680 off += state->regs[regno].imm;
682 size = bpf_size_to_bytes(bpf_size);
686 if (off % size != 0) {
687 verbose("misaligned access off %d size %d\n", off, size);
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);
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);
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);
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);
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);
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");
724 err = check_stack_write(state, off, size, value_regno);
726 err = check_stack_read(state, off, size, value_regno);
729 verbose("R%d invalid mem access '%s'\n",
730 regno, reg_type_str[state->regs[regno].type]);
736 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
738 struct reg_state *regs = env->cur_state.regs;
741 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
743 verbose("BPF_XADD uses reserved fields\n");
747 /* check src1 operand */
748 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
752 /* check src2 operand */
753 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
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);
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);
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
772 static int check_stack_boundary(struct verifier_env *env,
773 int regno, int access_size)
775 struct verifier_state *state = &env->cur_state;
776 struct reg_state *regs = state->regs;
779 if (regs[regno].type != PTR_TO_STACK)
782 off = regs[regno].imm;
783 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
785 verbose("invalid stack type R%d off=%d access_size=%d\n",
786 regno, off, access_size);
790 for (i = 0; i < access_size; i++) {
791 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
792 verbose("invalid indirect read from stack off %d+%d size %d\n",
793 off, i, access_size);
800 static int check_func_arg(struct verifier_env *env, u32 regno,
801 enum bpf_arg_type arg_type, struct bpf_map **mapp)
803 struct reg_state *reg = env->cur_state.regs + regno;
804 enum bpf_reg_type expected_type;
807 if (arg_type == ARG_DONTCARE)
810 if (reg->type == NOT_INIT) {
811 verbose("R%d !read_ok\n", regno);
815 if (arg_type == ARG_ANYTHING) {
816 if (is_pointer_value(env, regno)) {
817 verbose("R%d leaks addr into helper function\n", regno);
823 if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
824 arg_type == ARG_PTR_TO_MAP_VALUE) {
825 expected_type = PTR_TO_STACK;
826 } else if (arg_type == ARG_CONST_STACK_SIZE) {
827 expected_type = CONST_IMM;
828 } else if (arg_type == ARG_CONST_MAP_PTR) {
829 expected_type = CONST_PTR_TO_MAP;
830 } else if (arg_type == ARG_PTR_TO_CTX) {
831 expected_type = PTR_TO_CTX;
833 verbose("unsupported arg_type %d\n", arg_type);
837 if (reg->type != expected_type) {
838 verbose("R%d type=%s expected=%s\n", regno,
839 reg_type_str[reg->type], reg_type_str[expected_type]);
843 if (arg_type == ARG_CONST_MAP_PTR) {
844 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
845 *mapp = reg->map_ptr;
847 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
848 /* bpf_map_xxx(..., map_ptr, ..., key) call:
849 * check that [key, key + map->key_size) are within
850 * stack limits and initialized
853 /* in function declaration map_ptr must come before
854 * map_key, so that it's verified and known before
855 * we have to check map_key here. Otherwise it means
856 * that kernel subsystem misconfigured verifier
858 verbose("invalid map_ptr to access map->key\n");
861 err = check_stack_boundary(env, regno, (*mapp)->key_size);
863 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
864 /* bpf_map_xxx(..., map_ptr, ..., value) call:
865 * check [value, value + map->value_size) validity
868 /* kernel subsystem misconfigured verifier */
869 verbose("invalid map_ptr to access map->value\n");
872 err = check_stack_boundary(env, regno, (*mapp)->value_size);
874 } else if (arg_type == ARG_CONST_STACK_SIZE) {
875 /* bpf_xxx(..., buf, len) call will access 'len' bytes
876 * from stack pointer 'buf'. Check it
877 * note: regno == len, regno - 1 == buf
880 /* kernel subsystem misconfigured verifier */
881 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
884 err = check_stack_boundary(env, regno - 1, reg->imm);
890 static int check_map_func_compatibility(struct bpf_map *map, int func_id)
895 /* We need a two way check, first is from map perspective ... */
896 switch (map->map_type) {
897 case BPF_MAP_TYPE_PROG_ARRAY:
898 if (func_id != BPF_FUNC_tail_call)
901 case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
902 if (func_id != BPF_FUNC_perf_event_read &&
903 func_id != BPF_FUNC_perf_event_output)
910 /* ... and second from the function itself. */
912 case BPF_FUNC_tail_call:
913 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
916 case BPF_FUNC_perf_event_read:
917 case BPF_FUNC_perf_event_output:
918 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
927 verbose("cannot pass map_type %d into func %d\n",
928 map->map_type, func_id);
932 static int check_call(struct verifier_env *env, int func_id)
934 struct verifier_state *state = &env->cur_state;
935 const struct bpf_func_proto *fn = NULL;
936 struct reg_state *regs = state->regs;
937 struct bpf_map *map = NULL;
938 struct reg_state *reg;
941 /* find function prototype */
942 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
943 verbose("invalid func %d\n", func_id);
947 if (env->prog->aux->ops->get_func_proto)
948 fn = env->prog->aux->ops->get_func_proto(func_id);
951 verbose("unknown func %d\n", func_id);
955 /* eBPF programs must be GPL compatible to use GPL-ed functions */
956 if (!env->prog->gpl_compatible && fn->gpl_only) {
957 verbose("cannot call GPL only function from proprietary program\n");
962 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map);
965 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map);
968 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map);
971 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map);
974 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map);
978 /* reset caller saved regs */
979 for (i = 0; i < CALLER_SAVED_REGS; i++) {
980 reg = regs + caller_saved[i];
981 reg->type = NOT_INIT;
985 /* update return register */
986 if (fn->ret_type == RET_INTEGER) {
987 regs[BPF_REG_0].type = UNKNOWN_VALUE;
988 } else if (fn->ret_type == RET_VOID) {
989 regs[BPF_REG_0].type = NOT_INIT;
990 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
991 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
992 /* remember map_ptr, so that check_map_access()
993 * can check 'value_size' boundary of memory access
994 * to map element returned from bpf_map_lookup_elem()
997 verbose("kernel subsystem misconfigured verifier\n");
1000 regs[BPF_REG_0].map_ptr = map;
1002 verbose("unknown return type %d of func %d\n",
1003 fn->ret_type, func_id);
1007 err = check_map_func_compatibility(map, func_id);
1014 /* check validity of 32-bit and 64-bit arithmetic operations */
1015 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn)
1017 struct reg_state *regs = env->cur_state.regs;
1018 u8 opcode = BPF_OP(insn->code);
1021 if (opcode == BPF_END || opcode == BPF_NEG) {
1022 if (opcode == BPF_NEG) {
1023 if (BPF_SRC(insn->code) != 0 ||
1024 insn->src_reg != BPF_REG_0 ||
1025 insn->off != 0 || insn->imm != 0) {
1026 verbose("BPF_NEG uses reserved fields\n");
1030 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1031 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1032 verbose("BPF_END uses reserved fields\n");
1037 /* check src operand */
1038 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1042 if (is_pointer_value(env, insn->dst_reg)) {
1043 verbose("R%d pointer arithmetic prohibited\n",
1048 /* check dest operand */
1049 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1053 } else if (opcode == BPF_MOV) {
1055 if (BPF_SRC(insn->code) == BPF_X) {
1056 if (insn->imm != 0 || insn->off != 0) {
1057 verbose("BPF_MOV uses reserved fields\n");
1061 /* check src operand */
1062 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1066 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1067 verbose("BPF_MOV uses reserved fields\n");
1072 /* check dest operand */
1073 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1077 if (BPF_SRC(insn->code) == BPF_X) {
1078 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1080 * copy register state to dest reg
1082 regs[insn->dst_reg] = regs[insn->src_reg];
1084 if (is_pointer_value(env, insn->src_reg)) {
1085 verbose("R%d partial copy of pointer\n",
1089 regs[insn->dst_reg].type = UNKNOWN_VALUE;
1090 regs[insn->dst_reg].map_ptr = NULL;
1094 * remember the value we stored into this reg
1096 regs[insn->dst_reg].type = CONST_IMM;
1097 regs[insn->dst_reg].imm = insn->imm;
1100 } else if (opcode > BPF_END) {
1101 verbose("invalid BPF_ALU opcode %x\n", opcode);
1104 } else { /* all other ALU ops: and, sub, xor, add, ... */
1106 bool stack_relative = false;
1108 if (BPF_SRC(insn->code) == BPF_X) {
1109 if (insn->imm != 0 || insn->off != 0) {
1110 verbose("BPF_ALU uses reserved fields\n");
1113 /* check src1 operand */
1114 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1118 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1119 verbose("BPF_ALU uses reserved fields\n");
1124 /* check src2 operand */
1125 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1129 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1130 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1131 verbose("div by zero\n");
1135 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1136 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1137 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1139 if (insn->imm < 0 || insn->imm >= size) {
1140 verbose("invalid shift %d\n", insn->imm);
1145 /* pattern match 'bpf_add Rx, imm' instruction */
1146 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1147 regs[insn->dst_reg].type == FRAME_PTR &&
1148 BPF_SRC(insn->code) == BPF_K) {
1149 stack_relative = true;
1150 } else if (is_pointer_value(env, insn->dst_reg)) {
1151 verbose("R%d pointer arithmetic prohibited\n",
1154 } else if (BPF_SRC(insn->code) == BPF_X &&
1155 is_pointer_value(env, insn->src_reg)) {
1156 verbose("R%d pointer arithmetic prohibited\n",
1161 /* check dest operand */
1162 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1166 if (stack_relative) {
1167 regs[insn->dst_reg].type = PTR_TO_STACK;
1168 regs[insn->dst_reg].imm = insn->imm;
1175 static int check_cond_jmp_op(struct verifier_env *env,
1176 struct bpf_insn *insn, int *insn_idx)
1178 struct reg_state *regs = env->cur_state.regs;
1179 struct verifier_state *other_branch;
1180 u8 opcode = BPF_OP(insn->code);
1183 if (opcode > BPF_EXIT) {
1184 verbose("invalid BPF_JMP opcode %x\n", opcode);
1188 if (BPF_SRC(insn->code) == BPF_X) {
1189 if (insn->imm != 0) {
1190 verbose("BPF_JMP uses reserved fields\n");
1194 /* check src1 operand */
1195 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1199 if (is_pointer_value(env, insn->src_reg)) {
1200 verbose("R%d pointer comparison prohibited\n",
1205 if (insn->src_reg != BPF_REG_0) {
1206 verbose("BPF_JMP uses reserved fields\n");
1211 /* check src2 operand */
1212 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1216 /* detect if R == 0 where R was initialized to zero earlier */
1217 if (BPF_SRC(insn->code) == BPF_K &&
1218 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1219 regs[insn->dst_reg].type == CONST_IMM &&
1220 regs[insn->dst_reg].imm == insn->imm) {
1221 if (opcode == BPF_JEQ) {
1222 /* if (imm == imm) goto pc+off;
1223 * only follow the goto, ignore fall-through
1225 *insn_idx += insn->off;
1228 /* if (imm != imm) goto pc+off;
1229 * only follow fall-through branch, since
1230 * that's where the program will go
1236 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1240 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1241 if (BPF_SRC(insn->code) == BPF_K &&
1242 insn->imm == 0 && (opcode == BPF_JEQ ||
1243 opcode == BPF_JNE) &&
1244 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1245 if (opcode == BPF_JEQ) {
1246 /* next fallthrough insn can access memory via
1249 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1250 /* branch targer cannot access it, since reg == 0 */
1251 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1252 other_branch->regs[insn->dst_reg].imm = 0;
1254 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1255 regs[insn->dst_reg].type = CONST_IMM;
1256 regs[insn->dst_reg].imm = 0;
1258 } else if (is_pointer_value(env, insn->dst_reg)) {
1259 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
1261 } else if (BPF_SRC(insn->code) == BPF_K &&
1262 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1264 if (opcode == BPF_JEQ) {
1265 /* detect if (R == imm) goto
1266 * and in the target state recognize that R = imm
1268 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1269 other_branch->regs[insn->dst_reg].imm = insn->imm;
1271 /* detect if (R != imm) goto
1272 * and in the fall-through state recognize that R = imm
1274 regs[insn->dst_reg].type = CONST_IMM;
1275 regs[insn->dst_reg].imm = insn->imm;
1279 print_verifier_state(env);
1283 /* return the map pointer stored inside BPF_LD_IMM64 instruction */
1284 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1286 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1288 return (struct bpf_map *) (unsigned long) imm64;
1291 /* verify BPF_LD_IMM64 instruction */
1292 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1294 struct reg_state *regs = env->cur_state.regs;
1297 if (BPF_SIZE(insn->code) != BPF_DW) {
1298 verbose("invalid BPF_LD_IMM insn\n");
1301 if (insn->off != 0) {
1302 verbose("BPF_LD_IMM64 uses reserved fields\n");
1306 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1310 if (insn->src_reg == 0)
1311 /* generic move 64-bit immediate into a register */
1314 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1315 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1317 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1318 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1322 static bool may_access_skb(enum bpf_prog_type type)
1325 case BPF_PROG_TYPE_SOCKET_FILTER:
1326 case BPF_PROG_TYPE_SCHED_CLS:
1327 case BPF_PROG_TYPE_SCHED_ACT:
1334 /* verify safety of LD_ABS|LD_IND instructions:
1335 * - they can only appear in the programs where ctx == skb
1336 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1337 * preserve R6-R9, and store return value into R0
1340 * ctx == skb == R6 == CTX
1343 * SRC == any register
1344 * IMM == 32-bit immediate
1347 * R0 - 8/16/32-bit skb data converted to cpu endianness
1349 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1351 struct reg_state *regs = env->cur_state.regs;
1352 u8 mode = BPF_MODE(insn->code);
1353 struct reg_state *reg;
1356 if (!may_access_skb(env->prog->type)) {
1357 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n");
1361 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
1362 BPF_SIZE(insn->code) == BPF_DW ||
1363 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1364 verbose("BPF_LD_ABS uses reserved fields\n");
1368 /* check whether implicit source operand (register R6) is readable */
1369 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1373 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1374 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1378 if (mode == BPF_IND) {
1379 /* check explicit source operand */
1380 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1385 /* reset caller saved regs to unreadable */
1386 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1387 reg = regs + caller_saved[i];
1388 reg->type = NOT_INIT;
1392 /* mark destination R0 register as readable, since it contains
1393 * the value fetched from the packet
1395 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1399 /* non-recursive DFS pseudo code
1400 * 1 procedure DFS-iterative(G,v):
1401 * 2 label v as discovered
1402 * 3 let S be a stack
1404 * 5 while S is not empty
1406 * 7 if t is what we're looking for:
1408 * 9 for all edges e in G.adjacentEdges(t) do
1409 * 10 if edge e is already labelled
1410 * 11 continue with the next edge
1411 * 12 w <- G.adjacentVertex(t,e)
1412 * 13 if vertex w is not discovered and not explored
1413 * 14 label e as tree-edge
1414 * 15 label w as discovered
1417 * 18 else if vertex w is discovered
1418 * 19 label e as back-edge
1420 * 21 // vertex w is explored
1421 * 22 label e as forward- or cross-edge
1422 * 23 label t as explored
1427 * 0x11 - discovered and fall-through edge labelled
1428 * 0x12 - discovered and fall-through and branch edges labelled
1439 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1441 static int *insn_stack; /* stack of insns to process */
1442 static int cur_stack; /* current stack index */
1443 static int *insn_state;
1445 /* t, w, e - match pseudo-code above:
1446 * t - index of current instruction
1447 * w - next instruction
1450 static int push_insn(int t, int w, int e, struct verifier_env *env)
1452 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1455 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1458 if (w < 0 || w >= env->prog->len) {
1459 verbose("jump out of range from insn %d to %d\n", t, w);
1464 /* mark branch target for state pruning */
1465 env->explored_states[w] = STATE_LIST_MARK;
1467 if (insn_state[w] == 0) {
1469 insn_state[t] = DISCOVERED | e;
1470 insn_state[w] = DISCOVERED;
1471 if (cur_stack >= env->prog->len)
1473 insn_stack[cur_stack++] = w;
1475 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1476 verbose("back-edge from insn %d to %d\n", t, w);
1478 } else if (insn_state[w] == EXPLORED) {
1479 /* forward- or cross-edge */
1480 insn_state[t] = DISCOVERED | e;
1482 verbose("insn state internal bug\n");
1488 /* non-recursive depth-first-search to detect loops in BPF program
1489 * loop == back-edge in directed graph
1491 static int check_cfg(struct verifier_env *env)
1493 struct bpf_insn *insns = env->prog->insnsi;
1494 int insn_cnt = env->prog->len;
1498 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1502 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1508 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1509 insn_stack[0] = 0; /* 0 is the first instruction */
1515 t = insn_stack[cur_stack - 1];
1517 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1518 u8 opcode = BPF_OP(insns[t].code);
1520 if (opcode == BPF_EXIT) {
1522 } else if (opcode == BPF_CALL) {
1523 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1528 } else if (opcode == BPF_JA) {
1529 if (BPF_SRC(insns[t].code) != BPF_K) {
1533 /* unconditional jump with single edge */
1534 ret = push_insn(t, t + insns[t].off + 1,
1540 /* tell verifier to check for equivalent states
1541 * after every call and jump
1543 if (t + 1 < insn_cnt)
1544 env->explored_states[t + 1] = STATE_LIST_MARK;
1546 /* conditional jump with two edges */
1547 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1553 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1560 /* all other non-branch instructions with single
1563 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1571 insn_state[t] = EXPLORED;
1572 if (cur_stack-- <= 0) {
1573 verbose("pop stack internal bug\n");
1580 for (i = 0; i < insn_cnt; i++) {
1581 if (insn_state[i] != EXPLORED) {
1582 verbose("unreachable insn %d\n", i);
1587 ret = 0; /* cfg looks good */
1595 /* compare two verifier states
1597 * all states stored in state_list are known to be valid, since
1598 * verifier reached 'bpf_exit' instruction through them
1600 * this function is called when verifier exploring different branches of
1601 * execution popped from the state stack. If it sees an old state that has
1602 * more strict register state and more strict stack state then this execution
1603 * branch doesn't need to be explored further, since verifier already
1604 * concluded that more strict state leads to valid finish.
1606 * Therefore two states are equivalent if register state is more conservative
1607 * and explored stack state is more conservative than the current one.
1610 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1611 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1613 * In other words if current stack state (one being explored) has more
1614 * valid slots than old one that already passed validation, it means
1615 * the verifier can stop exploring and conclude that current state is valid too
1617 * Similarly with registers. If explored state has register type as invalid
1618 * whereas register type in current state is meaningful, it means that
1619 * the current state will reach 'bpf_exit' instruction safely
1621 static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1625 for (i = 0; i < MAX_BPF_REG; i++) {
1626 if (memcmp(&old->regs[i], &cur->regs[i],
1627 sizeof(old->regs[0])) != 0) {
1628 if (old->regs[i].type == NOT_INIT ||
1629 (old->regs[i].type == UNKNOWN_VALUE &&
1630 cur->regs[i].type != NOT_INIT))
1636 for (i = 0; i < MAX_BPF_STACK; i++) {
1637 if (old->stack_slot_type[i] == STACK_INVALID)
1639 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1640 /* Ex: old explored (safe) state has STACK_SPILL in
1641 * this stack slot, but current has has STACK_MISC ->
1642 * this verifier states are not equivalent,
1643 * return false to continue verification of this path
1646 if (i % BPF_REG_SIZE)
1648 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1649 &cur->spilled_regs[i / BPF_REG_SIZE],
1650 sizeof(old->spilled_regs[0])))
1651 /* when explored and current stack slot types are
1652 * the same, check that stored pointers types
1653 * are the same as well.
1654 * Ex: explored safe path could have stored
1655 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1656 * but current path has stored:
1657 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1658 * such verifier states are not equivalent.
1659 * return false to continue verification of this path
1668 static int is_state_visited(struct verifier_env *env, int insn_idx)
1670 struct verifier_state_list *new_sl;
1671 struct verifier_state_list *sl;
1673 sl = env->explored_states[insn_idx];
1675 /* this 'insn_idx' instruction wasn't marked, so we will not
1676 * be doing state search here
1680 while (sl != STATE_LIST_MARK) {
1681 if (states_equal(&sl->state, &env->cur_state))
1682 /* reached equivalent register/stack state,
1689 /* there were no equivalent states, remember current one.
1690 * technically the current state is not proven to be safe yet,
1691 * but it will either reach bpf_exit (which means it's safe) or
1692 * it will be rejected. Since there are no loops, we won't be
1693 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1695 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1699 /* add new state to the head of linked list */
1700 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1701 new_sl->next = env->explored_states[insn_idx];
1702 env->explored_states[insn_idx] = new_sl;
1706 static int do_check(struct verifier_env *env)
1708 struct verifier_state *state = &env->cur_state;
1709 struct bpf_insn *insns = env->prog->insnsi;
1710 struct reg_state *regs = state->regs;
1711 int insn_cnt = env->prog->len;
1712 int insn_idx, prev_insn_idx = 0;
1713 int insn_processed = 0;
1714 bool do_print_state = false;
1716 init_reg_state(regs);
1719 struct bpf_insn *insn;
1723 if (insn_idx >= insn_cnt) {
1724 verbose("invalid insn idx %d insn_cnt %d\n",
1725 insn_idx, insn_cnt);
1729 insn = &insns[insn_idx];
1730 class = BPF_CLASS(insn->code);
1732 if (++insn_processed > 32768) {
1733 verbose("BPF program is too large. Proccessed %d insn\n",
1738 err = is_state_visited(env, insn_idx);
1742 /* found equivalent state, can prune the search */
1745 verbose("\nfrom %d to %d: safe\n",
1746 prev_insn_idx, insn_idx);
1748 verbose("%d: safe\n", insn_idx);
1750 goto process_bpf_exit;
1753 if (log_level && do_print_state) {
1754 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1755 print_verifier_state(env);
1756 do_print_state = false;
1760 verbose("%d: ", insn_idx);
1761 print_bpf_insn(insn);
1764 if (class == BPF_ALU || class == BPF_ALU64) {
1765 err = check_alu_op(env, insn);
1769 } else if (class == BPF_LDX) {
1770 enum bpf_reg_type src_reg_type;
1772 /* check for reserved fields is already done */
1774 /* check src operand */
1775 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1779 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1783 src_reg_type = regs[insn->src_reg].type;
1785 /* check that memory (src_reg + off) is readable,
1786 * the state of dst_reg will be updated by this func
1788 err = check_mem_access(env, insn->src_reg, insn->off,
1789 BPF_SIZE(insn->code), BPF_READ,
1794 if (BPF_SIZE(insn->code) != BPF_W) {
1799 if (insn->imm == 0) {
1801 * dst_reg = *(u32 *)(src_reg + off)
1802 * use reserved 'imm' field to mark this insn
1804 insn->imm = src_reg_type;
1806 } else if (src_reg_type != insn->imm &&
1807 (src_reg_type == PTR_TO_CTX ||
1808 insn->imm == PTR_TO_CTX)) {
1809 /* ABuser program is trying to use the same insn
1810 * dst_reg = *(u32*) (src_reg + off)
1811 * with different pointer types:
1812 * src_reg == ctx in one branch and
1813 * src_reg == stack|map in some other branch.
1816 verbose("same insn cannot be used with different pointers\n");
1820 } else if (class == BPF_STX) {
1821 enum bpf_reg_type dst_reg_type;
1823 if (BPF_MODE(insn->code) == BPF_XADD) {
1824 err = check_xadd(env, insn);
1831 /* check src1 operand */
1832 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1835 /* check src2 operand */
1836 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1840 dst_reg_type = regs[insn->dst_reg].type;
1842 /* check that memory (dst_reg + off) is writeable */
1843 err = check_mem_access(env, insn->dst_reg, insn->off,
1844 BPF_SIZE(insn->code), BPF_WRITE,
1849 if (insn->imm == 0) {
1850 insn->imm = dst_reg_type;
1851 } else if (dst_reg_type != insn->imm &&
1852 (dst_reg_type == PTR_TO_CTX ||
1853 insn->imm == PTR_TO_CTX)) {
1854 verbose("same insn cannot be used with different pointers\n");
1858 } else if (class == BPF_ST) {
1859 if (BPF_MODE(insn->code) != BPF_MEM ||
1860 insn->src_reg != BPF_REG_0) {
1861 verbose("BPF_ST uses reserved fields\n");
1864 /* check src operand */
1865 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1869 /* check that memory (dst_reg + off) is writeable */
1870 err = check_mem_access(env, insn->dst_reg, insn->off,
1871 BPF_SIZE(insn->code), BPF_WRITE,
1876 } else if (class == BPF_JMP) {
1877 u8 opcode = BPF_OP(insn->code);
1879 if (opcode == BPF_CALL) {
1880 if (BPF_SRC(insn->code) != BPF_K ||
1882 insn->src_reg != BPF_REG_0 ||
1883 insn->dst_reg != BPF_REG_0) {
1884 verbose("BPF_CALL uses reserved fields\n");
1888 err = check_call(env, insn->imm);
1892 } else if (opcode == BPF_JA) {
1893 if (BPF_SRC(insn->code) != BPF_K ||
1895 insn->src_reg != BPF_REG_0 ||
1896 insn->dst_reg != BPF_REG_0) {
1897 verbose("BPF_JA uses reserved fields\n");
1901 insn_idx += insn->off + 1;
1904 } else if (opcode == BPF_EXIT) {
1905 if (BPF_SRC(insn->code) != BPF_K ||
1907 insn->src_reg != BPF_REG_0 ||
1908 insn->dst_reg != BPF_REG_0) {
1909 verbose("BPF_EXIT uses reserved fields\n");
1913 /* eBPF calling convetion is such that R0 is used
1914 * to return the value from eBPF program.
1915 * Make sure that it's readable at this time
1916 * of bpf_exit, which means that program wrote
1917 * something into it earlier
1919 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
1923 if (is_pointer_value(env, BPF_REG_0)) {
1924 verbose("R0 leaks addr as return value\n");
1929 insn_idx = pop_stack(env, &prev_insn_idx);
1933 do_print_state = true;
1937 err = check_cond_jmp_op(env, insn, &insn_idx);
1941 } else if (class == BPF_LD) {
1942 u8 mode = BPF_MODE(insn->code);
1944 if (mode == BPF_ABS || mode == BPF_IND) {
1945 err = check_ld_abs(env, insn);
1949 } else if (mode == BPF_IMM) {
1950 err = check_ld_imm(env, insn);
1956 verbose("invalid BPF_LD mode\n");
1960 verbose("unknown insn class %d\n", class);
1970 /* look for pseudo eBPF instructions that access map FDs and
1971 * replace them with actual map pointers
1973 static int replace_map_fd_with_map_ptr(struct verifier_env *env)
1975 struct bpf_insn *insn = env->prog->insnsi;
1976 int insn_cnt = env->prog->len;
1979 for (i = 0; i < insn_cnt; i++, insn++) {
1980 if (BPF_CLASS(insn->code) == BPF_LDX &&
1981 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
1982 verbose("BPF_LDX uses reserved fields\n");
1986 if (BPF_CLASS(insn->code) == BPF_STX &&
1987 ((BPF_MODE(insn->code) != BPF_MEM &&
1988 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
1989 verbose("BPF_STX uses reserved fields\n");
1993 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
1994 struct bpf_map *map;
1997 if (i == insn_cnt - 1 || insn[1].code != 0 ||
1998 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2000 verbose("invalid bpf_ld_imm64 insn\n");
2004 if (insn->src_reg == 0)
2005 /* valid generic load 64-bit imm */
2008 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2009 verbose("unrecognized bpf_ld_imm64 insn\n");
2013 f = fdget(insn->imm);
2014 map = __bpf_map_get(f);
2016 verbose("fd %d is not pointing to valid bpf_map\n",
2018 return PTR_ERR(map);
2021 /* store map pointer inside BPF_LD_IMM64 instruction */
2022 insn[0].imm = (u32) (unsigned long) map;
2023 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2025 /* check whether we recorded this map already */
2026 for (j = 0; j < env->used_map_cnt; j++)
2027 if (env->used_maps[j] == map) {
2032 if (env->used_map_cnt >= MAX_USED_MAPS) {
2037 /* hold the map. If the program is rejected by verifier,
2038 * the map will be released by release_maps() or it
2039 * will be used by the valid program until it's unloaded
2040 * and all maps are released in free_bpf_prog_info()
2042 map = bpf_map_inc(map, false);
2045 return PTR_ERR(map);
2047 env->used_maps[env->used_map_cnt++] = map;
2056 /* now all pseudo BPF_LD_IMM64 instructions load valid
2057 * 'struct bpf_map *' into a register instead of user map_fd.
2058 * These pointers will be used later by verifier to validate map access.
2063 /* drop refcnt of maps used by the rejected program */
2064 static void release_maps(struct verifier_env *env)
2068 for (i = 0; i < env->used_map_cnt; i++)
2069 bpf_map_put(env->used_maps[i]);
2072 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2073 static void convert_pseudo_ld_imm64(struct verifier_env *env)
2075 struct bpf_insn *insn = env->prog->insnsi;
2076 int insn_cnt = env->prog->len;
2079 for (i = 0; i < insn_cnt; i++, insn++)
2080 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2084 static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
2086 struct bpf_insn *insn = prog->insnsi;
2087 int insn_cnt = prog->len;
2090 for (i = 0; i < insn_cnt; i++, insn++) {
2091 if (BPF_CLASS(insn->code) != BPF_JMP ||
2092 BPF_OP(insn->code) == BPF_CALL ||
2093 BPF_OP(insn->code) == BPF_EXIT)
2096 /* adjust offset of jmps if necessary */
2097 if (i < pos && i + insn->off + 1 > pos)
2099 else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
2104 /* convert load instructions that access fields of 'struct __sk_buff'
2105 * into sequence of instructions that access fields of 'struct sk_buff'
2107 static int convert_ctx_accesses(struct verifier_env *env)
2109 struct bpf_insn *insn = env->prog->insnsi;
2110 int insn_cnt = env->prog->len;
2111 struct bpf_insn insn_buf[16];
2112 struct bpf_prog *new_prog;
2115 enum bpf_access_type type;
2117 if (!env->prog->aux->ops->convert_ctx_access)
2120 for (i = 0; i < insn_cnt; i++, insn++) {
2121 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2123 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2128 if (insn->imm != PTR_TO_CTX) {
2129 /* clear internal mark */
2134 cnt = env->prog->aux->ops->
2135 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
2136 insn->off, insn_buf, env->prog);
2137 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2138 verbose("bpf verifier is misconfigured\n");
2143 memcpy(insn, insn_buf, sizeof(*insn));
2147 /* several new insns need to be inserted. Make room for them */
2148 insn_cnt += cnt - 1;
2149 new_prog = bpf_prog_realloc(env->prog,
2150 bpf_prog_size(insn_cnt),
2155 new_prog->len = insn_cnt;
2157 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2158 sizeof(*insn) * (insn_cnt - i - cnt));
2160 /* copy substitute insns in place of load instruction */
2161 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2163 /* adjust branches in the whole program */
2164 adjust_branches(new_prog, i, cnt - 1);
2166 /* keep walking new program and skip insns we just inserted */
2167 env->prog = new_prog;
2168 insn = new_prog->insnsi + i + cnt - 1;
2175 static void free_states(struct verifier_env *env)
2177 struct verifier_state_list *sl, *sln;
2180 if (!env->explored_states)
2183 for (i = 0; i < env->prog->len; i++) {
2184 sl = env->explored_states[i];
2187 while (sl != STATE_LIST_MARK) {
2194 kfree(env->explored_states);
2197 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
2199 char __user *log_ubuf = NULL;
2200 struct verifier_env *env;
2203 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
2206 /* 'struct verifier_env' can be global, but since it's not small,
2207 * allocate/free it every time bpf_check() is called
2209 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2215 /* grab the mutex to protect few globals used by verifier */
2216 mutex_lock(&bpf_verifier_lock);
2218 if (attr->log_level || attr->log_buf || attr->log_size) {
2219 /* user requested verbose verifier output
2220 * and supplied buffer to store the verification trace
2222 log_level = attr->log_level;
2223 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2224 log_size = attr->log_size;
2228 /* log_* values have to be sane */
2229 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2230 log_level == 0 || log_ubuf == NULL)
2234 log_buf = vmalloc(log_size);
2241 ret = replace_map_fd_with_map_ptr(env);
2243 goto skip_full_check;
2245 env->explored_states = kcalloc(env->prog->len,
2246 sizeof(struct verifier_state_list *),
2249 if (!env->explored_states)
2250 goto skip_full_check;
2252 ret = check_cfg(env);
2254 goto skip_full_check;
2256 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2258 ret = do_check(env);
2261 while (pop_stack(env, NULL) >= 0);
2265 /* program is valid, convert *(u32*)(ctx + off) accesses */
2266 ret = convert_ctx_accesses(env);
2268 if (log_level && log_len >= log_size - 1) {
2269 BUG_ON(log_len >= log_size);
2270 /* verifier log exceeded user supplied buffer */
2272 /* fall through to return what was recorded */
2275 /* copy verifier log back to user space including trailing zero */
2276 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2281 if (ret == 0 && env->used_map_cnt) {
2282 /* if program passed verifier, update used_maps in bpf_prog_info */
2283 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2284 sizeof(env->used_maps[0]),
2287 if (!env->prog->aux->used_maps) {
2292 memcpy(env->prog->aux->used_maps, env->used_maps,
2293 sizeof(env->used_maps[0]) * env->used_map_cnt);
2294 env->prog->aux->used_map_cnt = env->used_map_cnt;
2296 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2297 * bpf_ld_imm64 instructions
2299 convert_pseudo_ld_imm64(env);
2306 if (!env->prog->aux->used_maps)
2307 /* if we didn't copy map pointers into bpf_prog_info, release
2308 * them now. Otherwise free_bpf_prog_info() will release them.
2313 mutex_unlock(&bpf_verifier_lock);