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/system.h>
37 #include <asm/uaccess.h>
38 #include <asm/unaligned.h>
39 #include <linux/filter.h>
41 /* No hurry in this branch */
42 static void *__load_pointer(struct sk_buff
*skb
, int k
)
47 ptr
= skb_network_header(skb
) + k
- SKF_NET_OFF
;
48 else if (k
>= SKF_LL_OFF
)
49 ptr
= skb_mac_header(skb
) + k
- SKF_LL_OFF
;
51 if (ptr
>= skb
->head
&& ptr
< skb_tail_pointer(skb
))
56 static inline void *load_pointer(struct sk_buff
*skb
, int k
,
57 unsigned int size
, void *buffer
)
60 return skb_header_pointer(skb
, k
, size
, buffer
);
64 return __load_pointer(skb
, k
);
69 * sk_filter - run a packet through a socket filter
70 * @sk: sock associated with &sk_buff
71 * @skb: buffer to filter
73 * Run the filter code and then cut skb->data to correct size returned by
74 * sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
75 * than pkt_len we keep whole skb->data. This is the socket level
76 * wrapper to sk_run_filter. It returns 0 if the packet should
77 * be accepted or -EPERM if the packet should be tossed.
80 int sk_filter(struct sock
*sk
, struct sk_buff
*skb
)
83 struct sk_filter
*filter
;
85 err
= security_sock_rcv_skb(sk
, skb
);
90 filter
= rcu_dereference_bh(sk
->sk_filter
);
92 unsigned int pkt_len
= sk_run_filter(skb
, filter
->insns
, filter
->len
);
94 err
= pkt_len
? pskb_trim(skb
, pkt_len
) : -EPERM
;
100 EXPORT_SYMBOL(sk_filter
);
103 * sk_run_filter - run a filter on a socket
104 * @skb: buffer to run the filter on
105 * @filter: filter to apply
106 * @flen: length of filter
108 * Decode and apply filter instructions to the skb->data.
109 * Return length to keep, 0 for none. skb is the data we are
110 * filtering, filter is the array of filter instructions, and
111 * len is the number of filter blocks in the array.
113 unsigned int sk_run_filter(struct sk_buff
*skb
, struct sock_filter
*filter
, int flen
)
116 u32 A
= 0; /* Accumulator */
117 u32 X
= 0; /* Index Register */
118 u32 mem
[BPF_MEMWORDS
]; /* Scratch Memory Store */
119 unsigned long memvalid
= 0;
124 BUILD_BUG_ON(BPF_MEMWORDS
> BITS_PER_LONG
);
126 * Process array of filter instructions.
128 for (pc
= 0; pc
< flen
; pc
++) {
129 const struct sock_filter
*fentry
= &filter
[pc
];
132 switch (fentry
->code
) {
133 case BPF_S_ALU_ADD_X
:
136 case BPF_S_ALU_ADD_K
:
139 case BPF_S_ALU_SUB_X
:
142 case BPF_S_ALU_SUB_K
:
145 case BPF_S_ALU_MUL_X
:
148 case BPF_S_ALU_MUL_K
:
151 case BPF_S_ALU_DIV_X
:
156 case BPF_S_ALU_DIV_K
:
159 case BPF_S_ALU_AND_X
:
162 case BPF_S_ALU_AND_K
:
171 case BPF_S_ALU_LSH_X
:
174 case BPF_S_ALU_LSH_K
:
177 case BPF_S_ALU_RSH_X
:
180 case BPF_S_ALU_RSH_K
:
189 case BPF_S_JMP_JGT_K
:
190 pc
+= (A
> f_k
) ? fentry
->jt
: fentry
->jf
;
192 case BPF_S_JMP_JGE_K
:
193 pc
+= (A
>= f_k
) ? fentry
->jt
: fentry
->jf
;
195 case BPF_S_JMP_JEQ_K
:
196 pc
+= (A
== f_k
) ? fentry
->jt
: fentry
->jf
;
198 case BPF_S_JMP_JSET_K
:
199 pc
+= (A
& f_k
) ? fentry
->jt
: fentry
->jf
;
201 case BPF_S_JMP_JGT_X
:
202 pc
+= (A
> X
) ? fentry
->jt
: fentry
->jf
;
204 case BPF_S_JMP_JGE_X
:
205 pc
+= (A
>= X
) ? fentry
->jt
: fentry
->jf
;
207 case BPF_S_JMP_JEQ_X
:
208 pc
+= (A
== X
) ? fentry
->jt
: fentry
->jf
;
210 case BPF_S_JMP_JSET_X
:
211 pc
+= (A
& X
) ? fentry
->jt
: fentry
->jf
;
216 ptr
= load_pointer(skb
, k
, 4, &tmp
);
218 A
= get_unaligned_be32(ptr
);
225 ptr
= load_pointer(skb
, k
, 2, &tmp
);
227 A
= get_unaligned_be16(ptr
);
234 ptr
= load_pointer(skb
, k
, 1, &tmp
);
243 case BPF_S_LDX_W_LEN
:
255 case BPF_S_LDX_B_MSH
:
256 ptr
= load_pointer(skb
, f_k
, 1, &tmp
);
258 X
= (*(u8
*)ptr
& 0xf) << 2;
269 A
= (memvalid
& (1UL << f_k
)) ?
273 X
= (memvalid
& (1UL << f_k
)) ?
287 memvalid
|= 1UL << f_k
;
291 memvalid
|= 1UL << f_k
;
300 * Handle ancillary data, which are impossible
301 * (or very difficult) to get parsing packet contents.
303 switch (k
-SKF_AD_OFF
) {
304 case SKF_AD_PROTOCOL
:
305 A
= ntohs(skb
->protocol
);
313 A
= skb
->dev
->ifindex
;
319 A
= skb
->queue_mapping
;
326 case SKF_AD_NLATTR
: {
329 if (skb_is_nonlinear(skb
))
331 if (A
> skb
->len
- sizeof(struct nlattr
))
334 nla
= nla_find((struct nlattr
*)&skb
->data
[A
],
337 A
= (void *)nla
- (void *)skb
->data
;
342 case SKF_AD_NLATTR_NEST
: {
345 if (skb_is_nonlinear(skb
))
347 if (A
> skb
->len
- sizeof(struct nlattr
))
350 nla
= (struct nlattr
*)&skb
->data
[A
];
351 if (nla
->nla_len
> A
- skb
->len
)
354 nla
= nla_find_nested(nla
, X
);
356 A
= (void *)nla
- (void *)skb
->data
;
368 EXPORT_SYMBOL(sk_run_filter
);
371 * sk_chk_filter - verify socket filter code
372 * @filter: filter to verify
373 * @flen: length of filter
375 * Check the user's filter code. If we let some ugly
376 * filter code slip through kaboom! The filter must contain
377 * no references or jumps that are out of range, no illegal
378 * instructions, and must end with a RET instruction.
380 * All jumps are forward as they are not signed.
382 * Returns 0 if the rule set is legal or -EINVAL if not.
384 int sk_chk_filter(struct sock_filter
*filter
, int flen
)
386 struct sock_filter
*ftest
;
389 if (flen
== 0 || flen
> BPF_MAXINSNS
)
392 /* check the filter code now */
393 for (pc
= 0; pc
< flen
; pc
++) {
396 /* Only allow valid instructions */
397 switch (ftest
->code
) {
398 case BPF_ALU
|BPF_ADD
|BPF_K
:
399 ftest
->code
= BPF_S_ALU_ADD_K
;
401 case BPF_ALU
|BPF_ADD
|BPF_X
:
402 ftest
->code
= BPF_S_ALU_ADD_X
;
404 case BPF_ALU
|BPF_SUB
|BPF_K
:
405 ftest
->code
= BPF_S_ALU_SUB_K
;
407 case BPF_ALU
|BPF_SUB
|BPF_X
:
408 ftest
->code
= BPF_S_ALU_SUB_X
;
410 case BPF_ALU
|BPF_MUL
|BPF_K
:
411 ftest
->code
= BPF_S_ALU_MUL_K
;
413 case BPF_ALU
|BPF_MUL
|BPF_X
:
414 ftest
->code
= BPF_S_ALU_MUL_X
;
416 case BPF_ALU
|BPF_DIV
|BPF_X
:
417 ftest
->code
= BPF_S_ALU_DIV_X
;
419 case BPF_ALU
|BPF_AND
|BPF_K
:
420 ftest
->code
= BPF_S_ALU_AND_K
;
422 case BPF_ALU
|BPF_AND
|BPF_X
:
423 ftest
->code
= BPF_S_ALU_AND_X
;
425 case BPF_ALU
|BPF_OR
|BPF_K
:
426 ftest
->code
= BPF_S_ALU_OR_K
;
428 case BPF_ALU
|BPF_OR
|BPF_X
:
429 ftest
->code
= BPF_S_ALU_OR_X
;
431 case BPF_ALU
|BPF_LSH
|BPF_K
:
432 ftest
->code
= BPF_S_ALU_LSH_K
;
434 case BPF_ALU
|BPF_LSH
|BPF_X
:
435 ftest
->code
= BPF_S_ALU_LSH_X
;
437 case BPF_ALU
|BPF_RSH
|BPF_K
:
438 ftest
->code
= BPF_S_ALU_RSH_K
;
440 case BPF_ALU
|BPF_RSH
|BPF_X
:
441 ftest
->code
= BPF_S_ALU_RSH_X
;
443 case BPF_ALU
|BPF_NEG
:
444 ftest
->code
= BPF_S_ALU_NEG
;
446 case BPF_LD
|BPF_W
|BPF_ABS
:
447 ftest
->code
= BPF_S_LD_W_ABS
;
449 case BPF_LD
|BPF_H
|BPF_ABS
:
450 ftest
->code
= BPF_S_LD_H_ABS
;
452 case BPF_LD
|BPF_B
|BPF_ABS
:
453 ftest
->code
= BPF_S_LD_B_ABS
;
455 case BPF_LD
|BPF_W
|BPF_LEN
:
456 ftest
->code
= BPF_S_LD_W_LEN
;
458 case BPF_LD
|BPF_W
|BPF_IND
:
459 ftest
->code
= BPF_S_LD_W_IND
;
461 case BPF_LD
|BPF_H
|BPF_IND
:
462 ftest
->code
= BPF_S_LD_H_IND
;
464 case BPF_LD
|BPF_B
|BPF_IND
:
465 ftest
->code
= BPF_S_LD_B_IND
;
468 ftest
->code
= BPF_S_LD_IMM
;
470 case BPF_LDX
|BPF_W
|BPF_LEN
:
471 ftest
->code
= BPF_S_LDX_W_LEN
;
473 case BPF_LDX
|BPF_B
|BPF_MSH
:
474 ftest
->code
= BPF_S_LDX_B_MSH
;
476 case BPF_LDX
|BPF_IMM
:
477 ftest
->code
= BPF_S_LDX_IMM
;
479 case BPF_MISC
|BPF_TAX
:
480 ftest
->code
= BPF_S_MISC_TAX
;
482 case BPF_MISC
|BPF_TXA
:
483 ftest
->code
= BPF_S_MISC_TXA
;
486 ftest
->code
= BPF_S_RET_K
;
489 ftest
->code
= BPF_S_RET_A
;
492 /* Some instructions need special checks */
494 /* check for division by zero */
495 case BPF_ALU
|BPF_DIV
|BPF_K
:
498 ftest
->code
= BPF_S_ALU_DIV_K
;
501 /* check for invalid memory addresses */
503 if (ftest
->k
>= BPF_MEMWORDS
)
505 ftest
->code
= BPF_S_LD_MEM
;
507 case BPF_LDX
|BPF_MEM
:
508 if (ftest
->k
>= BPF_MEMWORDS
)
510 ftest
->code
= BPF_S_LDX_MEM
;
513 if (ftest
->k
>= BPF_MEMWORDS
)
515 ftest
->code
= BPF_S_ST
;
518 if (ftest
->k
>= BPF_MEMWORDS
)
520 ftest
->code
= BPF_S_STX
;
525 * Note, the large ftest->k might cause loops.
526 * Compare this with conditional jumps below,
527 * where offsets are limited. --ANK (981016)
529 if (ftest
->k
>= (unsigned)(flen
-pc
-1))
531 ftest
->code
= BPF_S_JMP_JA
;
534 case BPF_JMP
|BPF_JEQ
|BPF_K
:
535 ftest
->code
= BPF_S_JMP_JEQ_K
;
537 case BPF_JMP
|BPF_JEQ
|BPF_X
:
538 ftest
->code
= BPF_S_JMP_JEQ_X
;
540 case BPF_JMP
|BPF_JGE
|BPF_K
:
541 ftest
->code
= BPF_S_JMP_JGE_K
;
543 case BPF_JMP
|BPF_JGE
|BPF_X
:
544 ftest
->code
= BPF_S_JMP_JGE_X
;
546 case BPF_JMP
|BPF_JGT
|BPF_K
:
547 ftest
->code
= BPF_S_JMP_JGT_K
;
549 case BPF_JMP
|BPF_JGT
|BPF_X
:
550 ftest
->code
= BPF_S_JMP_JGT_X
;
552 case BPF_JMP
|BPF_JSET
|BPF_K
:
553 ftest
->code
= BPF_S_JMP_JSET_K
;
555 case BPF_JMP
|BPF_JSET
|BPF_X
:
556 ftest
->code
= BPF_S_JMP_JSET_X
;
563 /* for conditionals both must be safe */
564 switch (ftest
->code
) {
565 case BPF_S_JMP_JEQ_K
:
566 case BPF_S_JMP_JEQ_X
:
567 case BPF_S_JMP_JGE_K
:
568 case BPF_S_JMP_JGE_X
:
569 case BPF_S_JMP_JGT_K
:
570 case BPF_S_JMP_JGT_X
:
571 case BPF_S_JMP_JSET_X
:
572 case BPF_S_JMP_JSET_K
:
573 if (pc
+ ftest
->jt
+ 1 >= flen
||
574 pc
+ ftest
->jf
+ 1 >= flen
)
579 /* last instruction must be a RET code */
580 switch (filter
[flen
- 1].code
) {
589 EXPORT_SYMBOL(sk_chk_filter
);
592 * sk_filter_rcu_release - Release a socket filter by rcu_head
593 * @rcu: rcu_head that contains the sk_filter to free
595 static void sk_filter_rcu_release(struct rcu_head
*rcu
)
597 struct sk_filter
*fp
= container_of(rcu
, struct sk_filter
, rcu
);
599 sk_filter_release(fp
);
602 static void sk_filter_delayed_uncharge(struct sock
*sk
, struct sk_filter
*fp
)
604 unsigned int size
= sk_filter_len(fp
);
606 atomic_sub(size
, &sk
->sk_omem_alloc
);
607 call_rcu_bh(&fp
->rcu
, sk_filter_rcu_release
);
611 * sk_attach_filter - attach a socket filter
612 * @fprog: the filter program
613 * @sk: the socket to use
615 * Attach the user's filter code. We first run some sanity checks on
616 * it to make sure it does not explode on us later. If an error
617 * occurs or there is insufficient memory for the filter a negative
618 * errno code is returned. On success the return is zero.
620 int sk_attach_filter(struct sock_fprog
*fprog
, struct sock
*sk
)
622 struct sk_filter
*fp
, *old_fp
;
623 unsigned int fsize
= sizeof(struct sock_filter
) * fprog
->len
;
626 /* Make sure new filter is there and in the right amounts. */
627 if (fprog
->filter
== NULL
)
630 fp
= sock_kmalloc(sk
, fsize
+sizeof(*fp
), GFP_KERNEL
);
633 if (copy_from_user(fp
->insns
, fprog
->filter
, fsize
)) {
634 sock_kfree_s(sk
, fp
, fsize
+sizeof(*fp
));
638 atomic_set(&fp
->refcnt
, 1);
639 fp
->len
= fprog
->len
;
641 err
= sk_chk_filter(fp
->insns
, fp
->len
);
643 sk_filter_uncharge(sk
, fp
);
647 old_fp
= rcu_dereference_protected(sk
->sk_filter
,
648 sock_owned_by_user(sk
));
649 rcu_assign_pointer(sk
->sk_filter
, fp
);
652 sk_filter_delayed_uncharge(sk
, old_fp
);
655 EXPORT_SYMBOL_GPL(sk_attach_filter
);
657 int sk_detach_filter(struct sock
*sk
)
660 struct sk_filter
*filter
;
662 filter
= rcu_dereference_protected(sk
->sk_filter
,
663 sock_owned_by_user(sk
));
665 rcu_assign_pointer(sk
->sk_filter
, NULL
);
666 sk_filter_delayed_uncharge(sk
, filter
);
671 EXPORT_SYMBOL_GPL(sk_detach_filter
);
This page took 0.043326 seconds and 5 git commands to generate.