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 #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);