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1 /*
2  * Linux Socket Filter - Kernel level socket filtering
3  *
4  * Author:
5  *     Jay Schulist <jschlst@samba.org>
6  *
7  * Based on the design of:
8  *     - The Berkeley Packet Filter
9  *
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.
14  *
15  * Andi Kleen - Fix a few bad bugs and races.
16  * Kris Katterjohn - Added many additional checks in sk_chk_filter()
17  */
18
19 #include <linux/module.h>
20 #include <linux/types.h>
21 #include <linux/mm.h>
22 #include <linux/fcntl.h>
23 #include <linux/socket.h>
24 #include <linux/in.h>
25 #include <linux/inet.h>
26 #include <linux/netdevice.h>
27 #include <linux/if_packet.h>
28 #include <linux/gfp.h>
29 #include <net/ip.h>
30 #include <net/protocol.h>
31 #include <net/netlink.h>
32 #include <linux/skbuff.h>
33 #include <net/sock.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>
40 #include <linux/reciprocal_div.h>
41
42 enum {
43         BPF_S_RET_K = 1,
44         BPF_S_RET_A,
45         BPF_S_ALU_ADD_K,
46         BPF_S_ALU_ADD_X,
47         BPF_S_ALU_SUB_K,
48         BPF_S_ALU_SUB_X,
49         BPF_S_ALU_MUL_K,
50         BPF_S_ALU_MUL_X,
51         BPF_S_ALU_DIV_X,
52         BPF_S_ALU_AND_K,
53         BPF_S_ALU_AND_X,
54         BPF_S_ALU_OR_K,
55         BPF_S_ALU_OR_X,
56         BPF_S_ALU_LSH_K,
57         BPF_S_ALU_LSH_X,
58         BPF_S_ALU_RSH_K,
59         BPF_S_ALU_RSH_X,
60         BPF_S_ALU_NEG,
61         BPF_S_LD_W_ABS,
62         BPF_S_LD_H_ABS,
63         BPF_S_LD_B_ABS,
64         BPF_S_LD_W_LEN,
65         BPF_S_LD_W_IND,
66         BPF_S_LD_H_IND,
67         BPF_S_LD_B_IND,
68         BPF_S_LD_IMM,
69         BPF_S_LDX_W_LEN,
70         BPF_S_LDX_B_MSH,
71         BPF_S_LDX_IMM,
72         BPF_S_MISC_TAX,
73         BPF_S_MISC_TXA,
74         BPF_S_ALU_DIV_K,
75         BPF_S_LD_MEM,
76         BPF_S_LDX_MEM,
77         BPF_S_ST,
78         BPF_S_STX,
79         BPF_S_JMP_JA,
80         BPF_S_JMP_JEQ_K,
81         BPF_S_JMP_JEQ_X,
82         BPF_S_JMP_JGE_K,
83         BPF_S_JMP_JGE_X,
84         BPF_S_JMP_JGT_K,
85         BPF_S_JMP_JGT_X,
86         BPF_S_JMP_JSET_K,
87         BPF_S_JMP_JSET_X,
88 };
89
90 /* No hurry in this branch */
91 static void *__load_pointer(struct sk_buff *skb, int k)
92 {
93         u8 *ptr = NULL;
94
95         if (k >= SKF_NET_OFF)
96                 ptr = skb_network_header(skb) + k - SKF_NET_OFF;
97         else if (k >= SKF_LL_OFF)
98                 ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
99
100         if (ptr >= skb->head && ptr < skb_tail_pointer(skb))
101                 return ptr;
102         return NULL;
103 }
104
105 static inline void *load_pointer(struct sk_buff *skb, int k,
106                                  unsigned int size, void *buffer)
107 {
108         if (k >= 0)
109                 return skb_header_pointer(skb, k, size, buffer);
110         else {
111                 if (k >= SKF_AD_OFF)
112                         return NULL;
113                 return __load_pointer(skb, k);
114         }
115 }
116
117 /**
118  *      sk_filter - run a packet through a socket filter
119  *      @sk: sock associated with &sk_buff
120  *      @skb: buffer to filter
121  *
122  * Run the filter code and then cut skb->data to correct size returned by
123  * sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
124  * than pkt_len we keep whole skb->data. This is the socket level
125  * wrapper to sk_run_filter. It returns 0 if the packet should
126  * be accepted or -EPERM if the packet should be tossed.
127  *
128  */
129 int sk_filter(struct sock *sk, struct sk_buff *skb)
130 {
131         int err;
132         struct sk_filter *filter;
133
134         err = security_sock_rcv_skb(sk, skb);
135         if (err)
136                 return err;
137
138         rcu_read_lock_bh();
139         filter = rcu_dereference_bh(sk->sk_filter);
140         if (filter) {
141                 unsigned int pkt_len = sk_run_filter(skb, filter->insns);
142
143                 err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
144         }
145         rcu_read_unlock_bh();
146
147         return err;
148 }
149 EXPORT_SYMBOL(sk_filter);
150
151 /**
152  *      sk_run_filter - run a filter on a socket
153  *      @skb: buffer to run the filter on
154  *      @filter: filter to apply
155  *
156  * Decode and apply filter instructions to the skb->data.
157  * Return length to keep, 0 for none. @skb is the data we are
158  * filtering, @filter is the array of filter instructions.
159  * Because all jumps are guaranteed to be before last instruction,
160  * and last instruction guaranteed to be a RET, we dont need to check
161  * flen. (We used to pass to this function the length of filter)
162  */
163 unsigned int sk_run_filter(struct sk_buff *skb, const struct sock_filter *fentry)
164 {
165         void *ptr;
166         u32 A = 0;                      /* Accumulator */
167         u32 X = 0;                      /* Index Register */
168         u32 mem[BPF_MEMWORDS];          /* Scratch Memory Store */
169         unsigned long memvalid = 0;
170         u32 tmp;
171         int k;
172
173         BUILD_BUG_ON(BPF_MEMWORDS > BITS_PER_LONG);
174         /*
175          * Process array of filter instructions.
176          */
177         for (;; fentry++) {
178 #if defined(CONFIG_X86_32)
179 #define K (fentry->k)
180 #else
181                 const u32 K = fentry->k;
182 #endif
183
184                 switch (fentry->code) {
185                 case BPF_S_ALU_ADD_X:
186                         A += X;
187                         continue;
188                 case BPF_S_ALU_ADD_K:
189                         A += K;
190                         continue;
191                 case BPF_S_ALU_SUB_X:
192                         A -= X;
193                         continue;
194                 case BPF_S_ALU_SUB_K:
195                         A -= K;
196                         continue;
197                 case BPF_S_ALU_MUL_X:
198                         A *= X;
199                         continue;
200                 case BPF_S_ALU_MUL_K:
201                         A *= K;
202                         continue;
203                 case BPF_S_ALU_DIV_X:
204                         if (X == 0)
205                                 return 0;
206                         A /= X;
207                         continue;
208                 case BPF_S_ALU_DIV_K:
209                         A = reciprocal_divide(A, K);
210                         continue;
211                 case BPF_S_ALU_AND_X:
212                         A &= X;
213                         continue;
214                 case BPF_S_ALU_AND_K:
215                         A &= K;
216                         continue;
217                 case BPF_S_ALU_OR_X:
218                         A |= X;
219                         continue;
220                 case BPF_S_ALU_OR_K:
221                         A |= K;
222                         continue;
223                 case BPF_S_ALU_LSH_X:
224                         A <<= X;
225                         continue;
226                 case BPF_S_ALU_LSH_K:
227                         A <<= K;
228                         continue;
229                 case BPF_S_ALU_RSH_X:
230                         A >>= X;
231                         continue;
232                 case BPF_S_ALU_RSH_K:
233                         A >>= K;
234                         continue;
235                 case BPF_S_ALU_NEG:
236                         A = -A;
237                         continue;
238                 case BPF_S_JMP_JA:
239                         fentry += K;
240                         continue;
241                 case BPF_S_JMP_JGT_K:
242                         fentry += (A > K) ? fentry->jt : fentry->jf;
243                         continue;
244                 case BPF_S_JMP_JGE_K:
245                         fentry += (A >= K) ? fentry->jt : fentry->jf;
246                         continue;
247                 case BPF_S_JMP_JEQ_K:
248                         fentry += (A == K) ? fentry->jt : fentry->jf;
249                         continue;
250                 case BPF_S_JMP_JSET_K:
251                         fentry += (A & K) ? fentry->jt : fentry->jf;
252                         continue;
253                 case BPF_S_JMP_JGT_X:
254                         fentry += (A > X) ? fentry->jt : fentry->jf;
255                         continue;
256                 case BPF_S_JMP_JGE_X:
257                         fentry += (A >= X) ? fentry->jt : fentry->jf;
258                         continue;
259                 case BPF_S_JMP_JEQ_X:
260                         fentry += (A == X) ? fentry->jt : fentry->jf;
261                         continue;
262                 case BPF_S_JMP_JSET_X:
263                         fentry += (A & X) ? fentry->jt : fentry->jf;
264                         continue;
265                 case BPF_S_LD_W_ABS:
266                         k = K;
267 load_w:
268                         ptr = load_pointer(skb, k, 4, &tmp);
269                         if (ptr != NULL) {
270                                 A = get_unaligned_be32(ptr);
271                                 continue;
272                         }
273                         break;
274                 case BPF_S_LD_H_ABS:
275                         k = K;
276 load_h:
277                         ptr = load_pointer(skb, k, 2, &tmp);
278                         if (ptr != NULL) {
279                                 A = get_unaligned_be16(ptr);
280                                 continue;
281                         }
282                         break;
283                 case BPF_S_LD_B_ABS:
284                         k = K;
285 load_b:
286                         ptr = load_pointer(skb, k, 1, &tmp);
287                         if (ptr != NULL) {
288                                 A = *(u8 *)ptr;
289                                 continue;
290                         }
291                         break;
292                 case BPF_S_LD_W_LEN:
293                         A = skb->len;
294                         continue;
295                 case BPF_S_LDX_W_LEN:
296                         X = skb->len;
297                         continue;
298                 case BPF_S_LD_W_IND:
299                         k = X + K;
300                         goto load_w;
301                 case BPF_S_LD_H_IND:
302                         k = X + K;
303                         goto load_h;
304                 case BPF_S_LD_B_IND:
305                         k = X + K;
306                         goto load_b;
307                 case BPF_S_LDX_B_MSH:
308                         ptr = load_pointer(skb, K, 1, &tmp);
309                         if (ptr != NULL) {
310                                 X = (*(u8 *)ptr & 0xf) << 2;
311                                 continue;
312                         }
313                         return 0;
314                 case BPF_S_LD_IMM:
315                         A = K;
316                         continue;
317                 case BPF_S_LDX_IMM:
318                         X = K;
319                         continue;
320                 case BPF_S_LD_MEM:
321                         A = (memvalid & (1UL << K)) ?
322                                 mem[K] : 0;
323                         continue;
324                 case BPF_S_LDX_MEM:
325                         X = (memvalid & (1UL << K)) ?
326                                 mem[K] : 0;
327                         continue;
328                 case BPF_S_MISC_TAX:
329                         X = A;
330                         continue;
331                 case BPF_S_MISC_TXA:
332                         A = X;
333                         continue;
334                 case BPF_S_RET_K:
335                         return K;
336                 case BPF_S_RET_A:
337                         return A;
338                 case BPF_S_ST:
339                         memvalid |= 1UL << K;
340                         mem[K] = A;
341                         continue;
342                 case BPF_S_STX:
343                         memvalid |= 1UL << K;
344                         mem[K] = X;
345                         continue;
346                 default:
347                         WARN_ON(1);
348                         return 0;
349                 }
350
351                 /*
352                  * Handle ancillary data, which are impossible
353                  * (or very difficult) to get parsing packet contents.
354                  */
355                 switch (k-SKF_AD_OFF) {
356                 case SKF_AD_PROTOCOL:
357                         A = ntohs(skb->protocol);
358                         continue;
359                 case SKF_AD_PKTTYPE:
360                         A = skb->pkt_type;
361                         continue;
362                 case SKF_AD_IFINDEX:
363                         if (!skb->dev)
364                                 return 0;
365                         A = skb->dev->ifindex;
366                         continue;
367                 case SKF_AD_MARK:
368                         A = skb->mark;
369                         continue;
370                 case SKF_AD_QUEUE:
371                         A = skb->queue_mapping;
372                         continue;
373                 case SKF_AD_HATYPE:
374                         if (!skb->dev)
375                                 return 0;
376                         A = skb->dev->type;
377                         continue;
378                 case SKF_AD_RXHASH:
379                         A = skb->rxhash;
380                         continue;
381                 case SKF_AD_CPU:
382                         A = raw_smp_processor_id();
383                         continue;
384                 case SKF_AD_NLATTR: {
385                         struct nlattr *nla;
386
387                         if (skb_is_nonlinear(skb))
388                                 return 0;
389                         if (A > skb->len - sizeof(struct nlattr))
390                                 return 0;
391
392                         nla = nla_find((struct nlattr *)&skb->data[A],
393                                        skb->len - A, X);
394                         if (nla)
395                                 A = (void *)nla - (void *)skb->data;
396                         else
397                                 A = 0;
398                         continue;
399                 }
400                 case SKF_AD_NLATTR_NEST: {
401                         struct nlattr *nla;
402
403                         if (skb_is_nonlinear(skb))
404                                 return 0;
405                         if (A > skb->len - sizeof(struct nlattr))
406                                 return 0;
407
408                         nla = (struct nlattr *)&skb->data[A];
409                         if (nla->nla_len > A - skb->len)
410                                 return 0;
411
412                         nla = nla_find_nested(nla, X);
413                         if (nla)
414                                 A = (void *)nla - (void *)skb->data;
415                         else
416                                 A = 0;
417                         continue;
418                 }
419                 default:
420                         return 0;
421                 }
422         }
423
424         return 0;
425 }
426 EXPORT_SYMBOL(sk_run_filter);
427
428 /**
429  *      sk_chk_filter - verify socket filter code
430  *      @filter: filter to verify
431  *      @flen: length of filter
432  *
433  * Check the user's filter code. If we let some ugly
434  * filter code slip through kaboom! The filter must contain
435  * no references or jumps that are out of range, no illegal
436  * instructions, and must end with a RET instruction.
437  *
438  * All jumps are forward as they are not signed.
439  *
440  * Returns 0 if the rule set is legal or -EINVAL if not.
441  */
442 int sk_chk_filter(struct sock_filter *filter, int flen)
443 {
444         /*
445          * Valid instructions are initialized to non-0.
446          * Invalid instructions are initialized to 0.
447          */
448         static const u8 codes[] = {
449                 [BPF_ALU|BPF_ADD|BPF_K]  = BPF_S_ALU_ADD_K,
450                 [BPF_ALU|BPF_ADD|BPF_X]  = BPF_S_ALU_ADD_X,
451                 [BPF_ALU|BPF_SUB|BPF_K]  = BPF_S_ALU_SUB_K,
452                 [BPF_ALU|BPF_SUB|BPF_X]  = BPF_S_ALU_SUB_X,
453                 [BPF_ALU|BPF_MUL|BPF_K]  = BPF_S_ALU_MUL_K,
454                 [BPF_ALU|BPF_MUL|BPF_X]  = BPF_S_ALU_MUL_X,
455                 [BPF_ALU|BPF_DIV|BPF_X]  = BPF_S_ALU_DIV_X,
456                 [BPF_ALU|BPF_AND|BPF_K]  = BPF_S_ALU_AND_K,
457                 [BPF_ALU|BPF_AND|BPF_X]  = BPF_S_ALU_AND_X,
458                 [BPF_ALU|BPF_OR|BPF_K]   = BPF_S_ALU_OR_K,
459                 [BPF_ALU|BPF_OR|BPF_X]   = BPF_S_ALU_OR_X,
460                 [BPF_ALU|BPF_LSH|BPF_K]  = BPF_S_ALU_LSH_K,
461                 [BPF_ALU|BPF_LSH|BPF_X]  = BPF_S_ALU_LSH_X,
462                 [BPF_ALU|BPF_RSH|BPF_K]  = BPF_S_ALU_RSH_K,
463                 [BPF_ALU|BPF_RSH|BPF_X]  = BPF_S_ALU_RSH_X,
464                 [BPF_ALU|BPF_NEG]        = BPF_S_ALU_NEG,
465                 [BPF_LD|BPF_W|BPF_ABS]   = BPF_S_LD_W_ABS,
466                 [BPF_LD|BPF_H|BPF_ABS]   = BPF_S_LD_H_ABS,
467                 [BPF_LD|BPF_B|BPF_ABS]   = BPF_S_LD_B_ABS,
468                 [BPF_LD|BPF_W|BPF_LEN]   = BPF_S_LD_W_LEN,
469                 [BPF_LD|BPF_W|BPF_IND]   = BPF_S_LD_W_IND,
470                 [BPF_LD|BPF_H|BPF_IND]   = BPF_S_LD_H_IND,
471                 [BPF_LD|BPF_B|BPF_IND]   = BPF_S_LD_B_IND,
472                 [BPF_LD|BPF_IMM]         = BPF_S_LD_IMM,
473                 [BPF_LDX|BPF_W|BPF_LEN]  = BPF_S_LDX_W_LEN,
474                 [BPF_LDX|BPF_B|BPF_MSH]  = BPF_S_LDX_B_MSH,
475                 [BPF_LDX|BPF_IMM]        = BPF_S_LDX_IMM,
476                 [BPF_MISC|BPF_TAX]       = BPF_S_MISC_TAX,
477                 [BPF_MISC|BPF_TXA]       = BPF_S_MISC_TXA,
478                 [BPF_RET|BPF_K]          = BPF_S_RET_K,
479                 [BPF_RET|BPF_A]          = BPF_S_RET_A,
480                 [BPF_ALU|BPF_DIV|BPF_K]  = BPF_S_ALU_DIV_K,
481                 [BPF_LD|BPF_MEM]         = BPF_S_LD_MEM,
482                 [BPF_LDX|BPF_MEM]        = BPF_S_LDX_MEM,
483                 [BPF_ST]                 = BPF_S_ST,
484                 [BPF_STX]                = BPF_S_STX,
485                 [BPF_JMP|BPF_JA]         = BPF_S_JMP_JA,
486                 [BPF_JMP|BPF_JEQ|BPF_K]  = BPF_S_JMP_JEQ_K,
487                 [BPF_JMP|BPF_JEQ|BPF_X]  = BPF_S_JMP_JEQ_X,
488                 [BPF_JMP|BPF_JGE|BPF_K]  = BPF_S_JMP_JGE_K,
489                 [BPF_JMP|BPF_JGE|BPF_X]  = BPF_S_JMP_JGE_X,
490                 [BPF_JMP|BPF_JGT|BPF_K]  = BPF_S_JMP_JGT_K,
491                 [BPF_JMP|BPF_JGT|BPF_X]  = BPF_S_JMP_JGT_X,
492                 [BPF_JMP|BPF_JSET|BPF_K] = BPF_S_JMP_JSET_K,
493                 [BPF_JMP|BPF_JSET|BPF_X] = BPF_S_JMP_JSET_X,
494         };
495         int pc;
496
497         if (flen == 0 || flen > BPF_MAXINSNS)
498                 return -EINVAL;
499
500         /* check the filter code now */
501         for (pc = 0; pc < flen; pc++) {
502                 struct sock_filter *ftest = &filter[pc];
503                 u16 code = ftest->code;
504
505                 if (code >= ARRAY_SIZE(codes))
506                         return -EINVAL;
507                 code = codes[code];
508                 if (!code)
509                         return -EINVAL;
510                 /* Some instructions need special checks */
511                 switch (code) {
512                 case BPF_S_ALU_DIV_K:
513                         /* check for division by zero */
514                         if (ftest->k == 0)
515                                 return -EINVAL;
516                         ftest->k = reciprocal_value(ftest->k);
517                         break;
518                 case BPF_S_LD_MEM:
519                 case BPF_S_LDX_MEM:
520                 case BPF_S_ST:
521                 case BPF_S_STX:
522                         /* check for invalid memory addresses */
523                         if (ftest->k >= BPF_MEMWORDS)
524                                 return -EINVAL;
525                         break;
526                 case BPF_S_JMP_JA:
527                         /*
528                          * Note, the large ftest->k might cause loops.
529                          * Compare this with conditional jumps below,
530                          * where offsets are limited. --ANK (981016)
531                          */
532                         if (ftest->k >= (unsigned)(flen-pc-1))
533                                 return -EINVAL;
534                         break;
535                 case BPF_S_JMP_JEQ_K:
536                 case BPF_S_JMP_JEQ_X:
537                 case BPF_S_JMP_JGE_K:
538                 case BPF_S_JMP_JGE_X:
539                 case BPF_S_JMP_JGT_K:
540                 case BPF_S_JMP_JGT_X:
541                 case BPF_S_JMP_JSET_X:
542                 case BPF_S_JMP_JSET_K:
543                         /* for conditionals both must be safe */
544                         if (pc + ftest->jt + 1 >= flen ||
545                             pc + ftest->jf + 1 >= flen)
546                                 return -EINVAL;
547                         break;
548                 }
549                 ftest->code = code;
550         }
551
552         /* last instruction must be a RET code */
553         switch (filter[flen - 1].code) {
554         case BPF_S_RET_K:
555         case BPF_S_RET_A:
556                 return 0;
557         }
558         return -EINVAL;
559 }
560 EXPORT_SYMBOL(sk_chk_filter);
561
562 /**
563  *      sk_filter_rcu_release - Release a socket filter by rcu_head
564  *      @rcu: rcu_head that contains the sk_filter to free
565  */
566 static void sk_filter_rcu_release(struct rcu_head *rcu)
567 {
568         struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
569
570         sk_filter_release(fp);
571 }
572
573 static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp)
574 {
575         unsigned int size = sk_filter_len(fp);
576
577         atomic_sub(size, &sk->sk_omem_alloc);
578         call_rcu_bh(&fp->rcu, sk_filter_rcu_release);
579 }
580
581 /**
582  *      sk_attach_filter - attach a socket filter
583  *      @fprog: the filter program
584  *      @sk: the socket to use
585  *
586  * Attach the user's filter code. We first run some sanity checks on
587  * it to make sure it does not explode on us later. If an error
588  * occurs or there is insufficient memory for the filter a negative
589  * errno code is returned. On success the return is zero.
590  */
591 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
592 {
593         struct sk_filter *fp, *old_fp;
594         unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
595         int err;
596
597         /* Make sure new filter is there and in the right amounts. */
598         if (fprog->filter == NULL)
599                 return -EINVAL;
600
601         fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
602         if (!fp)
603                 return -ENOMEM;
604         if (copy_from_user(fp->insns, fprog->filter, fsize)) {
605                 sock_kfree_s(sk, fp, fsize+sizeof(*fp));
606                 return -EFAULT;
607         }
608
609         atomic_set(&fp->refcnt, 1);
610         fp->len = fprog->len;
611
612         err = sk_chk_filter(fp->insns, fp->len);
613         if (err) {
614                 sk_filter_uncharge(sk, fp);
615                 return err;
616         }
617
618         old_fp = rcu_dereference_protected(sk->sk_filter,
619                                            sock_owned_by_user(sk));
620         rcu_assign_pointer(sk->sk_filter, fp);
621
622         if (old_fp)
623                 sk_filter_delayed_uncharge(sk, old_fp);
624         return 0;
625 }
626 EXPORT_SYMBOL_GPL(sk_attach_filter);
627
628 int sk_detach_filter(struct sock *sk)
629 {
630         int ret = -ENOENT;
631         struct sk_filter *filter;
632
633         filter = rcu_dereference_protected(sk->sk_filter,
634                                            sock_owned_by_user(sk));
635         if (filter) {
636                 rcu_assign_pointer(sk->sk_filter, NULL);
637                 sk_filter_delayed_uncharge(sk, filter);
638                 ret = 0;
639         }
640         return ret;
641 }
642 EXPORT_SYMBOL_GPL(sk_detach_filter);