2 * Linux Socket Filter - Kernel level socket filtering
5 * Jay Schulist <jschlst@samba.org>
7 * Based on the design of:
8 * - The Berkeley Packet Filter
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version
13 * 2 of the License, or (at your option) any later version.
15 * Andi Kleen - Fix a few bad bugs and races.
16 * Kris Katterjohn - Added many additional checks in sk_chk_filter()
19 #include <linux/module.h>
20 #include <linux/types.h>
22 #include <linux/fcntl.h>
23 #include <linux/socket.h>
25 #include <linux/inet.h>
26 #include <linux/netdevice.h>
27 #include <linux/if_packet.h>
28 #include <linux/gfp.h>
30 #include <net/protocol.h>
31 #include <net/netlink.h>
32 #include <linux/skbuff.h>
34 #include <linux/errno.h>
35 #include <linux/timer.h>
36 #include <asm/uaccess.h>
37 #include <asm/unaligned.h>
38 #include <linux/filter.h>
39 #include <linux/reciprocal_div.h>
40 #include <linux/ratelimit.h>
41 #include <linux/seccomp.h>
43 /* No hurry in this branch
45 * Exported for the bpf jit load helper.
47 void *bpf_internal_load_pointer_neg_helper(const struct sk_buff
*skb
, int k
, unsigned int size
)
52 ptr
= skb_network_header(skb
) + k
- SKF_NET_OFF
;
53 else if (k
>= SKF_LL_OFF
)
54 ptr
= skb_mac_header(skb
) + k
- SKF_LL_OFF
;
56 if (ptr
>= skb
->head
&& ptr
+ size
<= skb_tail_pointer(skb
))
61 static inline void *load_pointer(const struct sk_buff
*skb
, int k
,
62 unsigned int size
, void *buffer
)
65 return skb_header_pointer(skb
, k
, size
, buffer
);
66 return bpf_internal_load_pointer_neg_helper(skb
, k
, size
);
70 * sk_filter - run a packet through a socket filter
71 * @sk: sock associated with &sk_buff
72 * @skb: buffer to filter
74 * Run the filter code and then cut skb->data to correct size returned by
75 * sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
76 * than pkt_len we keep whole skb->data. This is the socket level
77 * wrapper to sk_run_filter. It returns 0 if the packet should
78 * be accepted or -EPERM if the packet should be tossed.
81 int sk_filter(struct sock
*sk
, struct sk_buff
*skb
)
84 struct sk_filter
*filter
;
87 * If the skb was allocated from pfmemalloc reserves, only
88 * allow SOCK_MEMALLOC sockets to use it as this socket is
91 if (skb_pfmemalloc(skb
) && !sock_flag(sk
, SOCK_MEMALLOC
))
94 err
= security_sock_rcv_skb(sk
, skb
);
99 filter
= rcu_dereference(sk
->sk_filter
);
101 unsigned int pkt_len
= SK_RUN_FILTER(filter
, skb
);
103 err
= pkt_len
? pskb_trim(skb
, pkt_len
) : -EPERM
;
109 EXPORT_SYMBOL(sk_filter
);
112 * sk_run_filter - run a filter on a socket
113 * @skb: buffer to run the filter on
114 * @fentry: filter to apply
116 * Decode and apply filter instructions to the skb->data.
117 * Return length to keep, 0 for none. @skb is the data we are
118 * filtering, @filter is the array of filter instructions.
119 * Because all jumps are guaranteed to be before last instruction,
120 * and last instruction guaranteed to be a RET, we dont need to check
121 * flen. (We used to pass to this function the length of filter)
123 unsigned int sk_run_filter(const struct sk_buff
*skb
,
124 const struct sock_filter
*fentry
)
127 u32 A
= 0; /* Accumulator */
128 u32 X
= 0; /* Index Register */
129 u32 mem
[BPF_MEMWORDS
]; /* Scratch Memory Store */
134 * Process array of filter instructions.
137 #if defined(CONFIG_X86_32)
138 #define K (fentry->k)
140 const u32 K
= fentry
->k
;
143 switch (fentry
->code
) {
144 case BPF_S_ALU_ADD_X
:
147 case BPF_S_ALU_ADD_K
:
150 case BPF_S_ALU_SUB_X
:
153 case BPF_S_ALU_SUB_K
:
156 case BPF_S_ALU_MUL_X
:
159 case BPF_S_ALU_MUL_K
:
162 case BPF_S_ALU_DIV_X
:
167 case BPF_S_ALU_DIV_K
:
168 A
= reciprocal_divide(A
, K
);
170 case BPF_S_ALU_MOD_X
:
175 case BPF_S_ALU_MOD_K
:
178 case BPF_S_ALU_AND_X
:
181 case BPF_S_ALU_AND_K
:
190 case BPF_S_ANC_ALU_XOR_X
:
191 case BPF_S_ALU_XOR_X
:
194 case BPF_S_ALU_XOR_K
:
197 case BPF_S_ALU_LSH_X
:
200 case BPF_S_ALU_LSH_K
:
203 case BPF_S_ALU_RSH_X
:
206 case BPF_S_ALU_RSH_K
:
215 case BPF_S_JMP_JGT_K
:
216 fentry
+= (A
> K
) ? fentry
->jt
: fentry
->jf
;
218 case BPF_S_JMP_JGE_K
:
219 fentry
+= (A
>= K
) ? fentry
->jt
: fentry
->jf
;
221 case BPF_S_JMP_JEQ_K
:
222 fentry
+= (A
== K
) ? fentry
->jt
: fentry
->jf
;
224 case BPF_S_JMP_JSET_K
:
225 fentry
+= (A
& K
) ? fentry
->jt
: fentry
->jf
;
227 case BPF_S_JMP_JGT_X
:
228 fentry
+= (A
> X
) ? fentry
->jt
: fentry
->jf
;
230 case BPF_S_JMP_JGE_X
:
231 fentry
+= (A
>= X
) ? fentry
->jt
: fentry
->jf
;
233 case BPF_S_JMP_JEQ_X
:
234 fentry
+= (A
== X
) ? fentry
->jt
: fentry
->jf
;
236 case BPF_S_JMP_JSET_X
:
237 fentry
+= (A
& X
) ? fentry
->jt
: fentry
->jf
;
242 ptr
= load_pointer(skb
, k
, 4, &tmp
);
244 A
= get_unaligned_be32(ptr
);
251 ptr
= load_pointer(skb
, k
, 2, &tmp
);
253 A
= get_unaligned_be16(ptr
);
260 ptr
= load_pointer(skb
, k
, 1, &tmp
);
269 case BPF_S_LDX_W_LEN
:
281 case BPF_S_LDX_B_MSH
:
282 ptr
= load_pointer(skb
, K
, 1, &tmp
);
284 X
= (*(u8
*)ptr
& 0xf) << 2;
316 case BPF_S_ANC_PROTOCOL
:
317 A
= ntohs(skb
->protocol
);
319 case BPF_S_ANC_PKTTYPE
:
322 case BPF_S_ANC_IFINDEX
:
325 A
= skb
->dev
->ifindex
;
330 case BPF_S_ANC_QUEUE
:
331 A
= skb
->queue_mapping
;
333 case BPF_S_ANC_HATYPE
:
338 case BPF_S_ANC_RXHASH
:
342 A
= raw_smp_processor_id();
344 case BPF_S_ANC_NLATTR
: {
347 if (skb_is_nonlinear(skb
))
349 if (A
> skb
->len
- sizeof(struct nlattr
))
352 nla
= nla_find((struct nlattr
*)&skb
->data
[A
],
355 A
= (void *)nla
- (void *)skb
->data
;
360 case BPF_S_ANC_NLATTR_NEST
: {
363 if (skb_is_nonlinear(skb
))
365 if (A
> skb
->len
- sizeof(struct nlattr
))
368 nla
= (struct nlattr
*)&skb
->data
[A
];
369 if (nla
->nla_len
> A
- skb
->len
)
372 nla
= nla_find_nested(nla
, X
);
374 A
= (void *)nla
- (void *)skb
->data
;
379 #ifdef CONFIG_SECCOMP_FILTER
380 case BPF_S_ANC_SECCOMP_LD_W
:
381 A
= seccomp_bpf_load(fentry
->k
);
385 WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
386 fentry
->code
, fentry
->jt
,
387 fentry
->jf
, fentry
->k
);
394 EXPORT_SYMBOL(sk_run_filter
);
398 * A BPF program is able to use 16 cells of memory to store intermediate
399 * values (check u32 mem[BPF_MEMWORDS] in sk_run_filter())
400 * As we dont want to clear mem[] array for each packet going through
401 * sk_run_filter(), we check that filter loaded by user never try to read
402 * a cell if not previously written, and we check all branches to be sure
403 * a malicious user doesn't try to abuse us.
405 static int check_load_and_stores(struct sock_filter
*filter
, int flen
)
407 u16
*masks
, memvalid
= 0; /* one bit per cell, 16 cells */
410 BUILD_BUG_ON(BPF_MEMWORDS
> 16);
411 masks
= kmalloc(flen
* sizeof(*masks
), GFP_KERNEL
);
414 memset(masks
, 0xff, flen
* sizeof(*masks
));
416 for (pc
= 0; pc
< flen
; pc
++) {
417 memvalid
&= masks
[pc
];
419 switch (filter
[pc
].code
) {
422 memvalid
|= (1 << filter
[pc
].k
);
426 if (!(memvalid
& (1 << filter
[pc
].k
))) {
432 /* a jump must set masks on target */
433 masks
[pc
+ 1 + filter
[pc
].k
] &= memvalid
;
436 case BPF_S_JMP_JEQ_K
:
437 case BPF_S_JMP_JEQ_X
:
438 case BPF_S_JMP_JGE_K
:
439 case BPF_S_JMP_JGE_X
:
440 case BPF_S_JMP_JGT_K
:
441 case BPF_S_JMP_JGT_X
:
442 case BPF_S_JMP_JSET_X
:
443 case BPF_S_JMP_JSET_K
:
444 /* a jump must set masks on targets */
445 masks
[pc
+ 1 + filter
[pc
].jt
] &= memvalid
;
446 masks
[pc
+ 1 + filter
[pc
].jf
] &= memvalid
;
457 * sk_chk_filter - verify socket filter code
458 * @filter: filter to verify
459 * @flen: length of filter
461 * Check the user's filter code. If we let some ugly
462 * filter code slip through kaboom! The filter must contain
463 * no references or jumps that are out of range, no illegal
464 * instructions, and must end with a RET instruction.
466 * All jumps are forward as they are not signed.
468 * Returns 0 if the rule set is legal or -EINVAL if not.
470 int sk_chk_filter(struct sock_filter
*filter
, unsigned int flen
)
473 * Valid instructions are initialized to non-0.
474 * Invalid instructions are initialized to 0.
476 static const u8 codes
[] = {
477 [BPF_ALU
|BPF_ADD
|BPF_K
] = BPF_S_ALU_ADD_K
,
478 [BPF_ALU
|BPF_ADD
|BPF_X
] = BPF_S_ALU_ADD_X
,
479 [BPF_ALU
|BPF_SUB
|BPF_K
] = BPF_S_ALU_SUB_K
,
480 [BPF_ALU
|BPF_SUB
|BPF_X
] = BPF_S_ALU_SUB_X
,
481 [BPF_ALU
|BPF_MUL
|BPF_K
] = BPF_S_ALU_MUL_K
,
482 [BPF_ALU
|BPF_MUL
|BPF_X
] = BPF_S_ALU_MUL_X
,
483 [BPF_ALU
|BPF_DIV
|BPF_X
] = BPF_S_ALU_DIV_X
,
484 [BPF_ALU
|BPF_MOD
|BPF_K
] = BPF_S_ALU_MOD_K
,
485 [BPF_ALU
|BPF_MOD
|BPF_X
] = BPF_S_ALU_MOD_X
,
486 [BPF_ALU
|BPF_AND
|BPF_K
] = BPF_S_ALU_AND_K
,
487 [BPF_ALU
|BPF_AND
|BPF_X
] = BPF_S_ALU_AND_X
,
488 [BPF_ALU
|BPF_OR
|BPF_K
] = BPF_S_ALU_OR_K
,
489 [BPF_ALU
|BPF_OR
|BPF_X
] = BPF_S_ALU_OR_X
,
490 [BPF_ALU
|BPF_XOR
|BPF_K
] = BPF_S_ALU_XOR_K
,
491 [BPF_ALU
|BPF_XOR
|BPF_X
] = BPF_S_ALU_XOR_X
,
492 [BPF_ALU
|BPF_LSH
|BPF_K
] = BPF_S_ALU_LSH_K
,
493 [BPF_ALU
|BPF_LSH
|BPF_X
] = BPF_S_ALU_LSH_X
,
494 [BPF_ALU
|BPF_RSH
|BPF_K
] = BPF_S_ALU_RSH_K
,
495 [BPF_ALU
|BPF_RSH
|BPF_X
] = BPF_S_ALU_RSH_X
,
496 [BPF_ALU
|BPF_NEG
] = BPF_S_ALU_NEG
,
497 [BPF_LD
|BPF_W
|BPF_ABS
] = BPF_S_LD_W_ABS
,
498 [BPF_LD
|BPF_H
|BPF_ABS
] = BPF_S_LD_H_ABS
,
499 [BPF_LD
|BPF_B
|BPF_ABS
] = BPF_S_LD_B_ABS
,
500 [BPF_LD
|BPF_W
|BPF_LEN
] = BPF_S_LD_W_LEN
,
501 [BPF_LD
|BPF_W
|BPF_IND
] = BPF_S_LD_W_IND
,
502 [BPF_LD
|BPF_H
|BPF_IND
] = BPF_S_LD_H_IND
,
503 [BPF_LD
|BPF_B
|BPF_IND
] = BPF_S_LD_B_IND
,
504 [BPF_LD
|BPF_IMM
] = BPF_S_LD_IMM
,
505 [BPF_LDX
|BPF_W
|BPF_LEN
] = BPF_S_LDX_W_LEN
,
506 [BPF_LDX
|BPF_B
|BPF_MSH
] = BPF_S_LDX_B_MSH
,
507 [BPF_LDX
|BPF_IMM
] = BPF_S_LDX_IMM
,
508 [BPF_MISC
|BPF_TAX
] = BPF_S_MISC_TAX
,
509 [BPF_MISC
|BPF_TXA
] = BPF_S_MISC_TXA
,
510 [BPF_RET
|BPF_K
] = BPF_S_RET_K
,
511 [BPF_RET
|BPF_A
] = BPF_S_RET_A
,
512 [BPF_ALU
|BPF_DIV
|BPF_K
] = BPF_S_ALU_DIV_K
,
513 [BPF_LD
|BPF_MEM
] = BPF_S_LD_MEM
,
514 [BPF_LDX
|BPF_MEM
] = BPF_S_LDX_MEM
,
516 [BPF_STX
] = BPF_S_STX
,
517 [BPF_JMP
|BPF_JA
] = BPF_S_JMP_JA
,
518 [BPF_JMP
|BPF_JEQ
|BPF_K
] = BPF_S_JMP_JEQ_K
,
519 [BPF_JMP
|BPF_JEQ
|BPF_X
] = BPF_S_JMP_JEQ_X
,
520 [BPF_JMP
|BPF_JGE
|BPF_K
] = BPF_S_JMP_JGE_K
,
521 [BPF_JMP
|BPF_JGE
|BPF_X
] = BPF_S_JMP_JGE_X
,
522 [BPF_JMP
|BPF_JGT
|BPF_K
] = BPF_S_JMP_JGT_K
,
523 [BPF_JMP
|BPF_JGT
|BPF_X
] = BPF_S_JMP_JGT_X
,
524 [BPF_JMP
|BPF_JSET
|BPF_K
] = BPF_S_JMP_JSET_K
,
525 [BPF_JMP
|BPF_JSET
|BPF_X
] = BPF_S_JMP_JSET_X
,
529 if (flen
== 0 || flen
> BPF_MAXINSNS
)
532 /* check the filter code now */
533 for (pc
= 0; pc
< flen
; pc
++) {
534 struct sock_filter
*ftest
= &filter
[pc
];
535 u16 code
= ftest
->code
;
537 if (code
>= ARRAY_SIZE(codes
))
542 /* Some instructions need special checks */
544 case BPF_S_ALU_DIV_K
:
545 /* check for division by zero */
548 ftest
->k
= reciprocal_value(ftest
->k
);
550 case BPF_S_ALU_MOD_K
:
551 /* check for division by zero */
559 /* check for invalid memory addresses */
560 if (ftest
->k
>= BPF_MEMWORDS
)
565 * Note, the large ftest->k might cause loops.
566 * Compare this with conditional jumps below,
567 * where offsets are limited. --ANK (981016)
569 if (ftest
->k
>= (unsigned int)(flen
-pc
-1))
572 case BPF_S_JMP_JEQ_K
:
573 case BPF_S_JMP_JEQ_X
:
574 case BPF_S_JMP_JGE_K
:
575 case BPF_S_JMP_JGE_X
:
576 case BPF_S_JMP_JGT_K
:
577 case BPF_S_JMP_JGT_X
:
578 case BPF_S_JMP_JSET_X
:
579 case BPF_S_JMP_JSET_K
:
580 /* for conditionals both must be safe */
581 if (pc
+ ftest
->jt
+ 1 >= flen
||
582 pc
+ ftest
->jf
+ 1 >= flen
)
588 #define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE: \
589 code = BPF_S_ANC_##CODE; \
596 ANCILLARY(NLATTR_NEST
);
602 ANCILLARY(ALU_XOR_X
);
608 /* last instruction must be a RET code */
609 switch (filter
[flen
- 1].code
) {
612 return check_load_and_stores(filter
, flen
);
616 EXPORT_SYMBOL(sk_chk_filter
);
619 * sk_filter_release_rcu - Release a socket filter by rcu_head
620 * @rcu: rcu_head that contains the sk_filter to free
622 void sk_filter_release_rcu(struct rcu_head
*rcu
)
624 struct sk_filter
*fp
= container_of(rcu
, struct sk_filter
, rcu
);
629 EXPORT_SYMBOL(sk_filter_release_rcu
);
631 static int __sk_prepare_filter(struct sk_filter
*fp
)
635 fp
->bpf_func
= sk_run_filter
;
637 err
= sk_chk_filter(fp
->insns
, fp
->len
);
646 * sk_unattached_filter_create - create an unattached filter
647 * @fprog: the filter program
648 * @pfp: the unattached filter that is created
650 * Create a filter independent of any socket. We first run some
651 * sanity checks on it to make sure it does not explode on us later.
652 * If an error occurs or there is insufficient memory for the filter
653 * a negative errno code is returned. On success the return is zero.
655 int sk_unattached_filter_create(struct sk_filter
**pfp
,
656 struct sock_fprog
*fprog
)
658 struct sk_filter
*fp
;
659 unsigned int fsize
= sizeof(struct sock_filter
) * fprog
->len
;
662 /* Make sure new filter is there and in the right amounts. */
663 if (fprog
->filter
== NULL
)
666 fp
= kmalloc(fsize
+ sizeof(*fp
), GFP_KERNEL
);
669 memcpy(fp
->insns
, fprog
->filter
, fsize
);
671 atomic_set(&fp
->refcnt
, 1);
672 fp
->len
= fprog
->len
;
674 err
= __sk_prepare_filter(fp
);
684 EXPORT_SYMBOL_GPL(sk_unattached_filter_create
);
686 void sk_unattached_filter_destroy(struct sk_filter
*fp
)
688 sk_filter_release(fp
);
690 EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy
);
693 * sk_attach_filter - attach a socket filter
694 * @fprog: the filter program
695 * @sk: the socket to use
697 * Attach the user's filter code. We first run some sanity checks on
698 * it to make sure it does not explode on us later. If an error
699 * occurs or there is insufficient memory for the filter a negative
700 * errno code is returned. On success the return is zero.
702 int sk_attach_filter(struct sock_fprog
*fprog
, struct sock
*sk
)
704 struct sk_filter
*fp
, *old_fp
;
705 unsigned int fsize
= sizeof(struct sock_filter
) * fprog
->len
;
708 /* Make sure new filter is there and in the right amounts. */
709 if (fprog
->filter
== NULL
)
712 fp
= sock_kmalloc(sk
, fsize
+sizeof(*fp
), GFP_KERNEL
);
715 if (copy_from_user(fp
->insns
, fprog
->filter
, fsize
)) {
716 sock_kfree_s(sk
, fp
, fsize
+sizeof(*fp
));
720 atomic_set(&fp
->refcnt
, 1);
721 fp
->len
= fprog
->len
;
723 err
= __sk_prepare_filter(fp
);
725 sk_filter_uncharge(sk
, fp
);
729 old_fp
= rcu_dereference_protected(sk
->sk_filter
,
730 sock_owned_by_user(sk
));
731 rcu_assign_pointer(sk
->sk_filter
, fp
);
734 sk_filter_uncharge(sk
, old_fp
);
737 EXPORT_SYMBOL_GPL(sk_attach_filter
);
739 int sk_detach_filter(struct sock
*sk
)
742 struct sk_filter
*filter
;
744 filter
= rcu_dereference_protected(sk
->sk_filter
,
745 sock_owned_by_user(sk
));
747 RCU_INIT_POINTER(sk
->sk_filter
, NULL
);
748 sk_filter_uncharge(sk
, filter
);
753 EXPORT_SYMBOL_GPL(sk_detach_filter
);