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
);