net/core/filter.c

   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
  41 /* No hurry in this branch */
  42 static void *__load_pointer(struct sk_buff *skb, int k)
  43 {
  44         u8 *ptr = NULL;
  45
  46         if (k >= SKF_NET_OFF)
  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;
  50
  51         if (ptr >= skb->head && ptr < skb_tail_pointer(skb))
  52                 return ptr;
  53         return NULL;
  54 }
  55
  56 static inline void *load_pointer(struct sk_buff *skb, int k,
  57                                  unsigned int size, void *buffer)
  58 {
  59         if (k >= 0)
  60                 return skb_header_pointer(skb, k, size, buffer);
  61         else {
  62                 if (k >= SKF_AD_OFF)
  63                         return NULL;
  64                 return __load_pointer(skb, k);
  65         }
  66 }
  67
  68 /**
  69  *      sk_filter - run a packet through a socket filter
  70  *      @sk: sock associated with &sk_buff
  71  *      @skb: buffer to filter
  72  *
  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.
  78  *
  79  */
  80 int sk_filter(struct sock *sk, struct sk_buff *skb)
  81 {
  82         int err;
  83         struct sk_filter *filter;
  84
  85         err = security_sock_rcv_skb(sk, skb);
  86         if (err)
  87                 return err;
  88
  89         rcu_read_lock_bh();
  90         filter = rcu_dereference_bh(sk->sk_filter);
  91         if (filter) {
  92                 unsigned int pkt_len = sk_run_filter(skb, filter->insns,
  93                                 filter->len);
  94                 err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
  95         }
  96         rcu_read_unlock_bh();
  97
  98         return err;
  99 }
 100 EXPORT_SYMBOL(sk_filter);
 101
 102 /**
 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
 107  *
 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.
 112  */
 113 unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen)
 114 {
 115         void *ptr;
 116         u32 A = 0;                      /* Accumulator */
 117         u32 X = 0;                      /* Index Register */
 118         u32 mem[BPF_MEMWORDS];          /* Scratch Memory Store */
 119         unsigned long memvalid = 0;
 120         u32 tmp;
 121         int k;
 122         int pc;
 123
 124         BUILD_BUG_ON(BPF_MEMWORDS > BITS_PER_LONG);
 125         /*
 126          * Process array of filter instructions.
 127          */
 128         for (pc = 0; pc < flen; pc++) {
 129                 const struct sock_filter *fentry = &filter[pc];
 130                 u32 f_k = fentry->k;
 131
 132                 switch (fentry->code) {
 133                 case BPF_S_ALU_ADD_X:
 134                         A += X;
 135                         continue;
 136                 case BPF_S_ALU_ADD_K:
 137                         A += f_k;
 138                         continue;
 139                 case BPF_S_ALU_SUB_X:
 140                         A -= X;
 141                         continue;
 142                 case BPF_S_ALU_SUB_K:
 143                         A -= f_k;
 144                         continue;
 145                 case BPF_S_ALU_MUL_X:
 146                         A *= X;
 147                         continue;
 148                 case BPF_S_ALU_MUL_K:
 149                         A *= f_k;
 150                         continue;
 151                 case BPF_S_ALU_DIV_X:
 152                         if (X == 0)
 153                                 return 0;
 154                         A /= X;
 155                         continue;
 156                 case BPF_S_ALU_DIV_K:
 157                         A /= f_k;
 158                         continue;
 159                 case BPF_S_ALU_AND_X:
 160                         A &= X;
 161                         continue;
 162                 case BPF_S_ALU_AND_K:
 163                         A &= f_k;
 164                         continue;
 165                 case BPF_S_ALU_OR_X:
 166                         A |= X;
 167                         continue;
 168                 case BPF_S_ALU_OR_K:
 169                         A |= f_k;
 170                         continue;
 171                 case BPF_S_ALU_LSH_X:
 172                         A <<= X;
 173                         continue;
 174                 case BPF_S_ALU_LSH_K:
 175                         A <<= f_k;
 176                         continue;
 177                 case BPF_S_ALU_RSH_X:
 178                         A >>= X;
 179                         continue;
 180                 case BPF_S_ALU_RSH_K:
 181                         A >>= f_k;
 182                         continue;
 183                 case BPF_S_ALU_NEG:
 184                         A = -A;
 185                         continue;
 186                 case BPF_S_JMP_JA:
 187                         pc += f_k;
 188                         continue;
 189                 case BPF_S_JMP_JGT_K:
 190                         pc += (A > f_k) ? fentry->jt : fentry->jf;
 191                         continue;
 192                 case BPF_S_JMP_JGE_K:
 193                         pc += (A >= f_k) ? fentry->jt : fentry->jf;
 194                         continue;
 195                 case BPF_S_JMP_JEQ_K:
 196                         pc += (A == f_k) ? fentry->jt : fentry->jf;
 197                         continue;
 198                 case BPF_S_JMP_JSET_K:
 199                         pc += (A & f_k) ? fentry->jt : fentry->jf;
 200                         continue;
 201                 case BPF_S_JMP_JGT_X:
 202                         pc += (A > X) ? fentry->jt : fentry->jf;
 203                         continue;
 204                 case BPF_S_JMP_JGE_X:
 205                         pc += (A >= X) ? fentry->jt : fentry->jf;
 206                         continue;
 207                 case BPF_S_JMP_JEQ_X:
 208                         pc += (A == X) ? fentry->jt : fentry->jf;
 209                         continue;
 210                 case BPF_S_JMP_JSET_X:
 211                         pc += (A & X) ? fentry->jt : fentry->jf;
 212                         continue;
 213                 case BPF_S_LD_W_ABS:
 214                         k = f_k;
 215 load_w:
 216                         ptr = load_pointer(skb, k, 4, &tmp);
 217                         if (ptr != NULL) {
 218                                 A = get_unaligned_be32(ptr);
 219                                 continue;
 220                         }
 221                         break;
 222                 case BPF_S_LD_H_ABS:
 223                         k = f_k;
 224 load_h:
 225                         ptr = load_pointer(skb, k, 2, &tmp);
 226                         if (ptr != NULL) {
 227                                 A = get_unaligned_be16(ptr);
 228                                 continue;
 229                         }
 230                         break;
 231                 case BPF_S_LD_B_ABS:
 232                         k = f_k;
 233 load_b:
 234                         ptr = load_pointer(skb, k, 1, &tmp);
 235                         if (ptr != NULL) {
 236                                 A = *(u8 *)ptr;
 237                                 continue;
 238                         }
 239                         break;
 240                 case BPF_S_LD_W_LEN:
 241                         A = skb->len;
 242                         continue;
 243                 case BPF_S_LDX_W_LEN:
 244                         X = skb->len;
 245                         continue;
 246                 case BPF_S_LD_W_IND:
 247                         k = X + f_k;
 248                         goto load_w;
 249                 case BPF_S_LD_H_IND:
 250                         k = X + f_k;
 251                         goto load_h;
 252                 case BPF_S_LD_B_IND:
 253                         k = X + f_k;
 254                         goto load_b;
 255                 case BPF_S_LDX_B_MSH:
 256                         ptr = load_pointer(skb, f_k, 1, &tmp);
 257                         if (ptr != NULL) {
 258                                 X = (*(u8 *)ptr & 0xf) << 2;
 259                                 continue;
 260                         }
 261                         return 0;
 262                 case BPF_S_LD_IMM:
 263                         A = f_k;
 264                         continue;
 265                 case BPF_S_LDX_IMM:
 266                         X = f_k;
 267                         continue;
 268                 case BPF_S_LD_MEM:
 269                         A = (memvalid & (1UL << f_k)) ?
 270                                 mem[f_k] : 0;
 271                         continue;
 272                 case BPF_S_LDX_MEM:
 273                         X = (memvalid & (1UL << f_k)) ?
 274                                 mem[f_k] : 0;
 275                         continue;
 276                 case BPF_S_MISC_TAX:
 277                         X = A;
 278                         continue;
 279                 case BPF_S_MISC_TXA:
 280                         A = X;
 281                         continue;
 282                 case BPF_S_RET_K:
 283                         return f_k;
 284                 case BPF_S_RET_A:
 285                         return A;
 286                 case BPF_S_ST:
 287                         memvalid |= 1UL << f_k;
 288                         mem[f_k] = A;
 289                         continue;
 290                 case BPF_S_STX:
 291                         memvalid |= 1UL << f_k;
 292                         mem[f_k] = X;
 293                         continue;
 294                 default:
 295                         WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
 296                                        fentry->code, fentry->jt,
 297                                        fentry->jf, fentry->k);
 298                         return 0;
 299                 }
 300
 301                 /*
 302                  * Handle ancillary data, which are impossible
 303                  * (or very difficult) to get parsing packet contents.
 304                  */
 305                 switch (k-SKF_AD_OFF) {
 306                 case SKF_AD_PROTOCOL:
 307                         A = ntohs(skb->protocol);
 308                         continue;
 309                 case SKF_AD_PKTTYPE:
 310                         A = skb->pkt_type;
 311                         continue;
 312                 case SKF_AD_IFINDEX:
 313                         if (!skb->dev)
 314                                 return 0;
 315                         A = skb->dev->ifindex;
 316                         continue;
 317                 case SKF_AD_MARK:
 318                         A = skb->mark;
 319                         continue;
 320                 case SKF_AD_QUEUE:
 321                         A = skb->queue_mapping;
 322                         continue;
 323                 case SKF_AD_HATYPE:
 324                         if (!skb->dev)
 325                                 return 0;
 326                         A = skb->dev->type;
 327                         continue;
 328                 case SKF_AD_NLATTR: {
 329                         struct nlattr *nla;
 330
 331                         if (skb_is_nonlinear(skb))
 332                                 return 0;
 333                         if (A > skb->len - sizeof(struct nlattr))
 334                                 return 0;
 335
 336                         nla = nla_find((struct nlattr *)&skb->data[A],
 337                                        skb->len - A, X);
 338                         if (nla)
 339                                 A = (void *)nla - (void *)skb->data;
 340                         else
 341                                 A = 0;
 342                         continue;
 343                 }
 344                 case SKF_AD_NLATTR_NEST: {
 345                         struct nlattr *nla;
 346
 347                         if (skb_is_nonlinear(skb))
 348                                 return 0;
 349                         if (A > skb->len - sizeof(struct nlattr))
 350                                 return 0;
 351
 352                         nla = (struct nlattr *)&skb->data[A];
 353                         if (nla->nla_len > A - skb->len)
 354                                 return 0;
 355
 356                         nla = nla_find_nested(nla, X);
 357                         if (nla)
 358                                 A = (void *)nla - (void *)skb->data;
 359                         else
 360                                 A = 0;
 361                         continue;
 362                 }
 363                 default:
 364                         return 0;
 365                 }
 366         }
 367
 368         return 0;
 369 }
 370 EXPORT_SYMBOL(sk_run_filter);
 371
 372 /**
 373  *      sk_chk_filter - verify socket filter code
 374  *      @filter: filter to verify
 375  *      @flen: length of filter
 376  *
 377  * Check the user's filter code. If we let some ugly
 378  * filter code slip through kaboom! The filter must contain
 379  * no references or jumps that are out of range, no illegal
 380  * instructions, and must end with a RET instruction.
 381  *
 382  * All jumps are forward as they are not signed.
 383  *
 384  * Returns 0 if the rule set is legal or -EINVAL if not.
 385  */
 386 int sk_chk_filter(struct sock_filter *filter, int flen)
 387 {
 388         struct sock_filter *ftest;
 389         int pc;
 390
 391         if (flen == 0 || flen > BPF_MAXINSNS)
 392                 return -EINVAL;
 393
 394         /* check the filter code now */
 395         for (pc = 0; pc < flen; pc++) {
 396                 ftest = &filter[pc];
 397
 398                 /* Only allow valid instructions */
 399                 switch (ftest->code) {
 400                 case BPF_ALU|BPF_ADD|BPF_K:
 401                         ftest->code = BPF_S_ALU_ADD_K;
 402                         break;
 403                 case BPF_ALU|BPF_ADD|BPF_X:
 404                         ftest->code = BPF_S_ALU_ADD_X;
 405                         break;
 406                 case BPF_ALU|BPF_SUB|BPF_K:
 407                         ftest->code = BPF_S_ALU_SUB_K;
 408                         break;
 409                 case BPF_ALU|BPF_SUB|BPF_X:
 410                         ftest->code = BPF_S_ALU_SUB_X;
 411                         break;
 412                 case BPF_ALU|BPF_MUL|BPF_K:
 413                         ftest->code = BPF_S_ALU_MUL_K;
 414                         break;
 415                 case BPF_ALU|BPF_MUL|BPF_X:
 416                         ftest->code = BPF_S_ALU_MUL_X;
 417                         break;
 418                 case BPF_ALU|BPF_DIV|BPF_X:
 419                         ftest->code = BPF_S_ALU_DIV_X;
 420                         break;
 421                 case BPF_ALU|BPF_AND|BPF_K:
 422                         ftest->code = BPF_S_ALU_AND_K;
 423                         break;
 424                 case BPF_ALU|BPF_AND|BPF_X:
 425                         ftest->code = BPF_S_ALU_AND_X;
 426                         break;
 427                 case BPF_ALU|BPF_OR|BPF_K:
 428                         ftest->code = BPF_S_ALU_OR_K;
 429                         break;
 430                 case BPF_ALU|BPF_OR|BPF_X:
 431                         ftest->code = BPF_S_ALU_OR_X;
 432                         break;
 433                 case BPF_ALU|BPF_LSH|BPF_K:
 434                         ftest->code = BPF_S_ALU_LSH_K;
 435                         break;
 436                 case BPF_ALU|BPF_LSH|BPF_X:
 437                         ftest->code = BPF_S_ALU_LSH_X;
 438                         break;
 439                 case BPF_ALU|BPF_RSH|BPF_K:
 440                         ftest->code = BPF_S_ALU_RSH_K;
 441                         break;
 442                 case BPF_ALU|BPF_RSH|BPF_X:
 443                         ftest->code = BPF_S_ALU_RSH_X;
 444                         break;
 445                 case BPF_ALU|BPF_NEG:
 446                         ftest->code = BPF_S_ALU_NEG;
 447                         break;
 448                 case BPF_LD|BPF_W|BPF_ABS:
 449                         ftest->code = BPF_S_LD_W_ABS;
 450                         break;
 451                 case BPF_LD|BPF_H|BPF_ABS:
 452                         ftest->code = BPF_S_LD_H_ABS;
 453                         break;
 454                 case BPF_LD|BPF_B|BPF_ABS:
 455                         ftest->code = BPF_S_LD_B_ABS;
 456                         break;
 457                 case BPF_LD|BPF_W|BPF_LEN:
 458                         ftest->code = BPF_S_LD_W_LEN;
 459                         break;
 460                 case BPF_LD|BPF_W|BPF_IND:
 461                         ftest->code = BPF_S_LD_W_IND;
 462                         break;
 463                 case BPF_LD|BPF_H|BPF_IND:
 464                         ftest->code = BPF_S_LD_H_IND;
 465                         break;
 466                 case BPF_LD|BPF_B|BPF_IND:
 467                         ftest->code = BPF_S_LD_B_IND;
 468                         break;
 469                 case BPF_LD|BPF_IMM:
 470                         ftest->code = BPF_S_LD_IMM;
 471                         break;
 472                 case BPF_LDX|BPF_W|BPF_LEN:
 473                         ftest->code = BPF_S_LDX_W_LEN;
 474                         break;
 475                 case BPF_LDX|BPF_B|BPF_MSH:
 476                         ftest->code = BPF_S_LDX_B_MSH;
 477                         break;
 478                 case BPF_LDX|BPF_IMM:
 479                         ftest->code = BPF_S_LDX_IMM;
 480                         break;
 481                 case BPF_MISC|BPF_TAX:
 482                         ftest->code = BPF_S_MISC_TAX;
 483                         break;
 484                 case BPF_MISC|BPF_TXA:
 485                         ftest->code = BPF_S_MISC_TXA;
 486                         break;
 487                 case BPF_RET|BPF_K:
 488                         ftest->code = BPF_S_RET_K;
 489                         break;
 490                 case BPF_RET|BPF_A:
 491                         ftest->code = BPF_S_RET_A;
 492                         break;
 493
 494                 /* Some instructions need special checks */
 495
 496                         /* check for division by zero */
 497                 case BPF_ALU|BPF_DIV|BPF_K:
 498                         if (ftest->k == 0)
 499                                 return -EINVAL;
 500                         ftest->code = BPF_S_ALU_DIV_K;
 501                         break;
 502
 503                 /* check for invalid memory addresses */
 504                 case BPF_LD|BPF_MEM:
 505                         if (ftest->k >= BPF_MEMWORDS)
 506                                 return -EINVAL;
 507                         ftest->code = BPF_S_LD_MEM;
 508                         break;
 509                 case BPF_LDX|BPF_MEM:
 510                         if (ftest->k >= BPF_MEMWORDS)
 511                                 return -EINVAL;
 512                         ftest->code = BPF_S_LDX_MEM;
 513                         break;
 514                 case BPF_ST:
 515                         if (ftest->k >= BPF_MEMWORDS)
 516                                 return -EINVAL;
 517                         ftest->code = BPF_S_ST;
 518                         break;
 519                 case BPF_STX:
 520                         if (ftest->k >= BPF_MEMWORDS)
 521                                 return -EINVAL;
 522                         ftest->code = BPF_S_STX;
 523                         break;
 524
 525                 case BPF_JMP|BPF_JA:
 526                         /*
 527                          * Note, the large ftest->k might cause loops.
 528                          * Compare this with conditional jumps below,
 529                          * where offsets are limited. --ANK (981016)
 530                          */
 531                         if (ftest->k >= (unsigned)(flen-pc-1))
 532                                 return -EINVAL;
 533                         ftest->code = BPF_S_JMP_JA;
 534                         break;
 535
 536                 case BPF_JMP|BPF_JEQ|BPF_K:
 537                         ftest->code = BPF_S_JMP_JEQ_K;
 538                         break;
 539                 case BPF_JMP|BPF_JEQ|BPF_X:
 540                         ftest->code = BPF_S_JMP_JEQ_X;
 541                         break;
 542                 case BPF_JMP|BPF_JGE|BPF_K:
 543                         ftest->code = BPF_S_JMP_JGE_K;
 544                         break;
 545                 case BPF_JMP|BPF_JGE|BPF_X:
 546                         ftest->code = BPF_S_JMP_JGE_X;
 547                         break;
 548                 case BPF_JMP|BPF_JGT|BPF_K:
 549                         ftest->code = BPF_S_JMP_JGT_K;
 550                         break;
 551                 case BPF_JMP|BPF_JGT|BPF_X:
 552                         ftest->code = BPF_S_JMP_JGT_X;
 553                         break;
 554                 case BPF_JMP|BPF_JSET|BPF_K:
 555                         ftest->code = BPF_S_JMP_JSET_K;
 556                         break;
 557                 case BPF_JMP|BPF_JSET|BPF_X:
 558                         ftest->code = BPF_S_JMP_JSET_X;
 559                         break;
 560
 561                 default:
 562                         return -EINVAL;
 563                 }
 564
 565                         /* for conditionals both must be safe */
 566                 switch (ftest->code) {
 567                 case BPF_S_JMP_JEQ_K:
 568                 case BPF_S_JMP_JEQ_X:
 569                 case BPF_S_JMP_JGE_K:
 570                 case BPF_S_JMP_JGE_X:
 571                 case BPF_S_JMP_JGT_K:
 572                 case BPF_S_JMP_JGT_X:
 573                 case BPF_S_JMP_JSET_X:
 574                 case BPF_S_JMP_JSET_K:
 575                         if (pc + ftest->jt + 1 >= flen ||
 576                             pc + ftest->jf + 1 >= flen)
 577                                 return -EINVAL;
 578                 }
 579         }
 580
 581         /* last instruction must be a RET code */
 582         switch (filter[flen - 1].code) {
 583         case BPF_S_RET_K:
 584         case BPF_S_RET_A:
 585                 return 0;
 586                 break;
 587                 default:
 588                         return -EINVAL;
 589                 }
 590 }
 591 EXPORT_SYMBOL(sk_chk_filter);
 592
 593 /**
 594  *      sk_filter_release_rcu - Release a socket filter by rcu_head
 595  *      @rcu: rcu_head that contains the sk_filter to free
 596  */
 597 void sk_filter_release_rcu(struct rcu_head *rcu)
 598 {
 599         struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
 600
 601         kfree(fp);
 602 }
 603 EXPORT_SYMBOL(sk_filter_release_rcu);
 604
 605 /**
 606  *      sk_attach_filter - attach a socket filter
 607  *      @fprog: the filter program
 608  *      @sk: the socket to use
 609  *
 610  * Attach the user's filter code. We first run some sanity checks on
 611  * it to make sure it does not explode on us later. If an error
 612  * occurs or there is insufficient memory for the filter a negative
 613  * errno code is returned. On success the return is zero.
 614  */
 615 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 616 {
 617         struct sk_filter *fp, *old_fp;
 618         unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
 619         int err;
 620
 621         /* Make sure new filter is there and in the right amounts. */
 622         if (fprog->filter == NULL)
 623                 return -EINVAL;
 624
 625         fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
 626         if (!fp)
 627                 return -ENOMEM;
 628         if (copy_from_user(fp->insns, fprog->filter, fsize)) {
 629                 sock_kfree_s(sk, fp, fsize+sizeof(*fp));
 630                 return -EFAULT;
 631         }
 632
 633         atomic_set(&fp->refcnt, 1);
 634         fp->len = fprog->len;
 635
 636         err = sk_chk_filter(fp->insns, fp->len);
 637         if (err) {
 638                 sk_filter_uncharge(sk, fp);
 639                 return err;
 640         }
 641
 642         rcu_read_lock_bh();
 643         old_fp = rcu_dereference_bh(sk->sk_filter);
 644         rcu_assign_pointer(sk->sk_filter, fp);
 645         rcu_read_unlock_bh();
 646
 647         if (old_fp)
 648                 sk_filter_uncharge(sk, old_fp);
 649         return 0;
 650 }
 651 EXPORT_SYMBOL_GPL(sk_attach_filter);
 652
 653 int sk_detach_filter(struct sock *sk)
 654 {
 655         int ret = -ENOENT;
 656         struct sk_filter *filter;
 657
 658         rcu_read_lock_bh();
 659         filter = rcu_dereference_bh(sk->sk_filter);
 660         if (filter) {
 661                 rcu_assign_pointer(sk->sk_filter, NULL);
 662                 sk_filter_uncharge(sk, filter);
 663                 ret = 0;
 664         }
 665         rcu_read_unlock_bh();
 666         return ret;
 667 }
 668 EXPORT_SYMBOL_GPL(sk_detach_filter);