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/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>
  42
  43 /* No hurry in this branch
  44  *
  45  * Exported for the bpf jit load helper.
  46  */
  47 void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb, int k, unsigned int size)
  48 {
  49         u8 *ptr = NULL;
  50
  51         if (k >= SKF_NET_OFF)
  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;
  55
  56         if (ptr >= skb->head && ptr + size <= skb_tail_pointer(skb))
  57                 return ptr;
  58         return NULL;
  59 }
  60
  61 static inline void *load_pointer(const struct sk_buff *skb, int k,
  62                                  unsigned int size, void *buffer)
  63 {
  64         if (k >= 0)
  65                 return skb_header_pointer(skb, k, size, buffer);
  66         return bpf_internal_load_pointer_neg_helper(skb, k, size);
  67 }
  68
  69 /**
  70  *      sk_filter - run a packet through a socket filter
  71  *      @sk: sock associated with &sk_buff
  72  *      @skb: buffer to filter
  73  *
  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.
  79  *
  80  */
  81 int sk_filter(struct sock *sk, struct sk_buff *skb)
  82 {
  83         int err;
  84         struct sk_filter *filter;
  85
  86         /*
  87          * If the skb was allocated from pfmemalloc reserves, only
  88          * allow SOCK_MEMALLOC sockets to use it as this socket is
  89          * helping free memory
  90          */
  91         if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
  92                 return -ENOMEM;
  93
  94         err = security_sock_rcv_skb(sk, skb);
  95         if (err)
  96                 return err;
  97
  98         rcu_read_lock();
  99         filter = rcu_dereference(sk->sk_filter);
 100         if (filter) {
 101                 unsigned int pkt_len = SK_RUN_FILTER(filter, skb);
 102
 103                 err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
 104         }
 105         rcu_read_unlock();
 106
 107         return err;
 108 }
 109 EXPORT_SYMBOL(sk_filter);
 110
 111 /**
 112  *      sk_run_filter - run a filter on a socket
 113  *      @skb: buffer to run the filter on
 114  *      @fentry: filter to apply
 115  *
 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)
 122  */
 123 unsigned int sk_run_filter(const struct sk_buff *skb,
 124                            const struct sock_filter *fentry)
 125 {
 126         void *ptr;
 127         u32 A = 0;                      /* Accumulator */
 128         u32 X = 0;                      /* Index Register */
 129         u32 mem[BPF_MEMWORDS];          /* Scratch Memory Store */
 130         u32 tmp;
 131         int k;
 132
 133         /*
 134          * Process array of filter instructions.
 135          */
 136         for (;; fentry++) {
 137 #if defined(CONFIG_X86_32)
 138 #define K (fentry->k)
 139 #else
 140                 const u32 K = fentry->k;
 141 #endif
 142
 143                 switch (fentry->code) {
 144                 case BPF_S_ALU_ADD_X:
 145                         A += X;
 146                         continue;
 147                 case BPF_S_ALU_ADD_K:
 148                         A += K;
 149                         continue;
 150                 case BPF_S_ALU_SUB_X:
 151                         A -= X;
 152                         continue;
 153                 case BPF_S_ALU_SUB_K:
 154                         A -= K;
 155                         continue;
 156                 case BPF_S_ALU_MUL_X:
 157                         A *= X;
 158                         continue;
 159                 case BPF_S_ALU_MUL_K:
 160                         A *= K;
 161                         continue;
 162                 case BPF_S_ALU_DIV_X:
 163                         if (X == 0)
 164                                 return 0;
 165                         A /= X;
 166                         continue;
 167                 case BPF_S_ALU_DIV_K:
 168                         A = reciprocal_divide(A, K);
 169                         continue;
 170                 case BPF_S_ALU_AND_X:
 171                         A &= X;
 172                         continue;
 173                 case BPF_S_ALU_AND_K:
 174                         A &= K;
 175                         continue;
 176                 case BPF_S_ALU_OR_X:
 177                         A |= X;
 178                         continue;
 179                 case BPF_S_ALU_OR_K:
 180                         A |= K;
 181                         continue;
 182                 case BPF_S_ALU_LSH_X:
 183                         A <<= X;
 184                         continue;
 185                 case BPF_S_ALU_LSH_K:
 186                         A <<= K;
 187                         continue;
 188                 case BPF_S_ALU_RSH_X:
 189                         A >>= X;
 190                         continue;
 191                 case BPF_S_ALU_RSH_K:
 192                         A >>= K;
 193                         continue;
 194                 case BPF_S_ALU_NEG:
 195                         A = -A;
 196                         continue;
 197                 case BPF_S_JMP_JA:
 198                         fentry += K;
 199                         continue;
 200                 case BPF_S_JMP_JGT_K:
 201                         fentry += (A > K) ? fentry->jt : fentry->jf;
 202                         continue;
 203                 case BPF_S_JMP_JGE_K:
 204                         fentry += (A >= K) ? fentry->jt : fentry->jf;
 205                         continue;
 206                 case BPF_S_JMP_JEQ_K:
 207                         fentry += (A == K) ? fentry->jt : fentry->jf;
 208                         continue;
 209                 case BPF_S_JMP_JSET_K:
 210                         fentry += (A & K) ? fentry->jt : fentry->jf;
 211                         continue;
 212                 case BPF_S_JMP_JGT_X:
 213                         fentry += (A > X) ? fentry->jt : fentry->jf;
 214                         continue;
 215                 case BPF_S_JMP_JGE_X:
 216                         fentry += (A >= X) ? fentry->jt : fentry->jf;
 217                         continue;
 218                 case BPF_S_JMP_JEQ_X:
 219                         fentry += (A == X) ? fentry->jt : fentry->jf;
 220                         continue;
 221                 case BPF_S_JMP_JSET_X:
 222                         fentry += (A & X) ? fentry->jt : fentry->jf;
 223                         continue;
 224                 case BPF_S_LD_W_ABS:
 225                         k = K;
 226 load_w:
 227                         ptr = load_pointer(skb, k, 4, &tmp);
 228                         if (ptr != NULL) {
 229                                 A = get_unaligned_be32(ptr);
 230                                 continue;
 231                         }
 232                         return 0;
 233                 case BPF_S_LD_H_ABS:
 234                         k = K;
 235 load_h:
 236                         ptr = load_pointer(skb, k, 2, &tmp);
 237                         if (ptr != NULL) {
 238                                 A = get_unaligned_be16(ptr);
 239                                 continue;
 240                         }
 241                         return 0;
 242                 case BPF_S_LD_B_ABS:
 243                         k = K;
 244 load_b:
 245                         ptr = load_pointer(skb, k, 1, &tmp);
 246                         if (ptr != NULL) {
 247                                 A = *(u8 *)ptr;
 248                                 continue;
 249                         }
 250                         return 0;
 251                 case BPF_S_LD_W_LEN:
 252                         A = skb->len;
 253                         continue;
 254                 case BPF_S_LDX_W_LEN:
 255                         X = skb->len;
 256                         continue;
 257                 case BPF_S_LD_W_IND:
 258                         k = X + K;
 259                         goto load_w;
 260                 case BPF_S_LD_H_IND:
 261                         k = X + K;
 262                         goto load_h;
 263                 case BPF_S_LD_B_IND:
 264                         k = X + K;
 265                         goto load_b;
 266                 case BPF_S_LDX_B_MSH:
 267                         ptr = load_pointer(skb, K, 1, &tmp);
 268                         if (ptr != NULL) {
 269                                 X = (*(u8 *)ptr & 0xf) << 2;
 270                                 continue;
 271                         }
 272                         return 0;
 273                 case BPF_S_LD_IMM:
 274                         A = K;
 275                         continue;
 276                 case BPF_S_LDX_IMM:
 277                         X = K;
 278                         continue;
 279                 case BPF_S_LD_MEM:
 280                         A = mem[K];
 281                         continue;
 282                 case BPF_S_LDX_MEM:
 283                         X = mem[K];
 284                         continue;
 285                 case BPF_S_MISC_TAX:
 286                         X = A;
 287                         continue;
 288                 case BPF_S_MISC_TXA:
 289                         A = X;
 290                         continue;
 291                 case BPF_S_RET_K:
 292                         return K;
 293                 case BPF_S_RET_A:
 294                         return A;
 295                 case BPF_S_ST:
 296                         mem[K] = A;
 297                         continue;
 298                 case BPF_S_STX:
 299                         mem[K] = X;
 300                         continue;
 301                 case BPF_S_ANC_PROTOCOL:
 302                         A = ntohs(skb->protocol);
 303                         continue;
 304                 case BPF_S_ANC_PKTTYPE:
 305                         A = skb->pkt_type;
 306                         continue;
 307                 case BPF_S_ANC_IFINDEX:
 308                         if (!skb->dev)
 309                                 return 0;
 310                         A = skb->dev->ifindex;
 311                         continue;
 312                 case BPF_S_ANC_MARK:
 313                         A = skb->mark;
 314                         continue;
 315                 case BPF_S_ANC_QUEUE:
 316                         A = skb->queue_mapping;
 317                         continue;
 318                 case BPF_S_ANC_HATYPE:
 319                         if (!skb->dev)
 320                                 return 0;
 321                         A = skb->dev->type;
 322                         continue;
 323                 case BPF_S_ANC_RXHASH:
 324                         A = skb->rxhash;
 325                         continue;
 326                 case BPF_S_ANC_CPU:
 327                         A = raw_smp_processor_id();
 328                         continue;
 329                 case BPF_S_ANC_ALU_XOR_X:
 330                         A ^= X;
 331                         continue;
 332                 case BPF_S_ANC_NLATTR: {
 333                         struct nlattr *nla;
 334
 335                         if (skb_is_nonlinear(skb))
 336                                 return 0;
 337                         if (A > skb->len - sizeof(struct nlattr))
 338                                 return 0;
 339
 340                         nla = nla_find((struct nlattr *)&skb->data[A],
 341                                        skb->len - A, X);
 342                         if (nla)
 343                                 A = (void *)nla - (void *)skb->data;
 344                         else
 345                                 A = 0;
 346                         continue;
 347                 }
 348                 case BPF_S_ANC_NLATTR_NEST: {
 349                         struct nlattr *nla;
 350
 351                         if (skb_is_nonlinear(skb))
 352                                 return 0;
 353                         if (A > skb->len - sizeof(struct nlattr))
 354                                 return 0;
 355
 356                         nla = (struct nlattr *)&skb->data[A];
 357                         if (nla->nla_len > A - skb->len)
 358                                 return 0;
 359
 360                         nla = nla_find_nested(nla, X);
 361                         if (nla)
 362                                 A = (void *)nla - (void *)skb->data;
 363                         else
 364                                 A = 0;
 365                         continue;
 366                 }
 367 #ifdef CONFIG_SECCOMP_FILTER
 368                 case BPF_S_ANC_SECCOMP_LD_W:
 369                         A = seccomp_bpf_load(fentry->k);
 370                         continue;
 371 #endif
 372                 default:
 373                         WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
 374                                        fentry->code, fentry->jt,
 375                                        fentry->jf, fentry->k);
 376                         return 0;
 377                 }
 378         }
 379
 380         return 0;
 381 }
 382 EXPORT_SYMBOL(sk_run_filter);
 383
 384 /*
 385  * Security :
 386  * A BPF program is able to use 16 cells of memory to store intermediate
 387  * values (check u32 mem[BPF_MEMWORDS] in sk_run_filter())
 388  * As we dont want to clear mem[] array for each packet going through
 389  * sk_run_filter(), we check that filter loaded by user never try to read
 390  * a cell if not previously written, and we check all branches to be sure
 391  * a malicious user doesn't try to abuse us.
 392  */
 393 static int check_load_and_stores(struct sock_filter *filter, int flen)
 394 {
 395         u16 *masks, memvalid = 0; /* one bit per cell, 16 cells */
 396         int pc, ret = 0;
 397
 398         BUILD_BUG_ON(BPF_MEMWORDS > 16);
 399         masks = kmalloc(flen * sizeof(*masks), GFP_KERNEL);
 400         if (!masks)
 401                 return -ENOMEM;
 402         memset(masks, 0xff, flen * sizeof(*masks));
 403
 404         for (pc = 0; pc < flen; pc++) {
 405                 memvalid &= masks[pc];
 406
 407                 switch (filter[pc].code) {
 408                 case BPF_S_ST:
 409                 case BPF_S_STX:
 410                         memvalid |= (1 << filter[pc].k);
 411                         break;
 412                 case BPF_S_LD_MEM:
 413                 case BPF_S_LDX_MEM:
 414                         if (!(memvalid & (1 << filter[pc].k))) {
 415                                 ret = -EINVAL;
 416                                 goto error;
 417                         }
 418                         break;
 419                 case BPF_S_JMP_JA:
 420                         /* a jump must set masks on target */
 421                         masks[pc + 1 + filter[pc].k] &= memvalid;
 422                         memvalid = ~0;
 423                         break;
 424                 case BPF_S_JMP_JEQ_K:
 425                 case BPF_S_JMP_JEQ_X:
 426                 case BPF_S_JMP_JGE_K:
 427                 case BPF_S_JMP_JGE_X:
 428                 case BPF_S_JMP_JGT_K:
 429                 case BPF_S_JMP_JGT_X:
 430                 case BPF_S_JMP_JSET_X:
 431                 case BPF_S_JMP_JSET_K:
 432                         /* a jump must set masks on targets */
 433                         masks[pc + 1 + filter[pc].jt] &= memvalid;
 434                         masks[pc + 1 + filter[pc].jf] &= memvalid;
 435                         memvalid = ~0;
 436                         break;
 437                 }
 438         }
 439 error:
 440         kfree(masks);
 441         return ret;
 442 }
 443
 444 /**
 445  *      sk_chk_filter - verify socket filter code
 446  *      @filter: filter to verify
 447  *      @flen: length of filter
 448  *
 449  * Check the user's filter code. If we let some ugly
 450  * filter code slip through kaboom! The filter must contain
 451  * no references or jumps that are out of range, no illegal
 452  * instructions, and must end with a RET instruction.
 453  *
 454  * All jumps are forward as they are not signed.
 455  *
 456  * Returns 0 if the rule set is legal or -EINVAL if not.
 457  */
 458 int sk_chk_filter(struct sock_filter *filter, unsigned int flen)
 459 {
 460         /*
 461          * Valid instructions are initialized to non-0.
 462          * Invalid instructions are initialized to 0.
 463          */
 464         static const u8 codes[] = {
 465                 [BPF_ALU|BPF_ADD|BPF_K]  = BPF_S_ALU_ADD_K,
 466                 [BPF_ALU|BPF_ADD|BPF_X]  = BPF_S_ALU_ADD_X,
 467                 [BPF_ALU|BPF_SUB|BPF_K]  = BPF_S_ALU_SUB_K,
 468                 [BPF_ALU|BPF_SUB|BPF_X]  = BPF_S_ALU_SUB_X,
 469                 [BPF_ALU|BPF_MUL|BPF_K]  = BPF_S_ALU_MUL_K,
 470                 [BPF_ALU|BPF_MUL|BPF_X]  = BPF_S_ALU_MUL_X,
 471                 [BPF_ALU|BPF_DIV|BPF_X]  = BPF_S_ALU_DIV_X,
 472                 [BPF_ALU|BPF_AND|BPF_K]  = BPF_S_ALU_AND_K,
 473                 [BPF_ALU|BPF_AND|BPF_X]  = BPF_S_ALU_AND_X,
 474                 [BPF_ALU|BPF_OR|BPF_K]   = BPF_S_ALU_OR_K,
 475                 [BPF_ALU|BPF_OR|BPF_X]   = BPF_S_ALU_OR_X,
 476                 [BPF_ALU|BPF_LSH|BPF_K]  = BPF_S_ALU_LSH_K,
 477                 [BPF_ALU|BPF_LSH|BPF_X]  = BPF_S_ALU_LSH_X,
 478                 [BPF_ALU|BPF_RSH|BPF_K]  = BPF_S_ALU_RSH_K,
 479                 [BPF_ALU|BPF_RSH|BPF_X]  = BPF_S_ALU_RSH_X,
 480                 [BPF_ALU|BPF_NEG]        = BPF_S_ALU_NEG,
 481                 [BPF_LD|BPF_W|BPF_ABS]   = BPF_S_LD_W_ABS,
 482                 [BPF_LD|BPF_H|BPF_ABS]   = BPF_S_LD_H_ABS,
 483                 [BPF_LD|BPF_B|BPF_ABS]   = BPF_S_LD_B_ABS,
 484                 [BPF_LD|BPF_W|BPF_LEN]   = BPF_S_LD_W_LEN,
 485                 [BPF_LD|BPF_W|BPF_IND]   = BPF_S_LD_W_IND,
 486                 [BPF_LD|BPF_H|BPF_IND]   = BPF_S_LD_H_IND,
 487                 [BPF_LD|BPF_B|BPF_IND]   = BPF_S_LD_B_IND,
 488                 [BPF_LD|BPF_IMM]         = BPF_S_LD_IMM,
 489                 [BPF_LDX|BPF_W|BPF_LEN]  = BPF_S_LDX_W_LEN,
 490                 [BPF_LDX|BPF_B|BPF_MSH]  = BPF_S_LDX_B_MSH,
 491                 [BPF_LDX|BPF_IMM]        = BPF_S_LDX_IMM,
 492                 [BPF_MISC|BPF_TAX]       = BPF_S_MISC_TAX,
 493                 [BPF_MISC|BPF_TXA]       = BPF_S_MISC_TXA,
 494                 [BPF_RET|BPF_K]          = BPF_S_RET_K,
 495                 [BPF_RET|BPF_A]          = BPF_S_RET_A,
 496                 [BPF_ALU|BPF_DIV|BPF_K]  = BPF_S_ALU_DIV_K,
 497                 [BPF_LD|BPF_MEM]         = BPF_S_LD_MEM,
 498                 [BPF_LDX|BPF_MEM]        = BPF_S_LDX_MEM,
 499                 [BPF_ST]                 = BPF_S_ST,
 500                 [BPF_STX]                = BPF_S_STX,
 501                 [BPF_JMP|BPF_JA]         = BPF_S_JMP_JA,
 502                 [BPF_JMP|BPF_JEQ|BPF_K]  = BPF_S_JMP_JEQ_K,
 503                 [BPF_JMP|BPF_JEQ|BPF_X]  = BPF_S_JMP_JEQ_X,
 504                 [BPF_JMP|BPF_JGE|BPF_K]  = BPF_S_JMP_JGE_K,
 505                 [BPF_JMP|BPF_JGE|BPF_X]  = BPF_S_JMP_JGE_X,
 506                 [BPF_JMP|BPF_JGT|BPF_K]  = BPF_S_JMP_JGT_K,
 507                 [BPF_JMP|BPF_JGT|BPF_X]  = BPF_S_JMP_JGT_X,
 508                 [BPF_JMP|BPF_JSET|BPF_K] = BPF_S_JMP_JSET_K,
 509                 [BPF_JMP|BPF_JSET|BPF_X] = BPF_S_JMP_JSET_X,
 510         };
 511         int pc;
 512
 513         if (flen == 0 || flen > BPF_MAXINSNS)
 514                 return -EINVAL;
 515
 516         /* check the filter code now */
 517         for (pc = 0; pc < flen; pc++) {
 518                 struct sock_filter *ftest = &filter[pc];
 519                 u16 code = ftest->code;
 520
 521                 if (code >= ARRAY_SIZE(codes))
 522                         return -EINVAL;
 523                 code = codes[code];
 524                 if (!code)
 525                         return -EINVAL;
 526                 /* Some instructions need special checks */
 527                 switch (code) {
 528                 case BPF_S_ALU_DIV_K:
 529                         /* check for division by zero */
 530                         if (ftest->k == 0)
 531                                 return -EINVAL;
 532                         ftest->k = reciprocal_value(ftest->k);
 533                         break;
 534                 case BPF_S_LD_MEM:
 535                 case BPF_S_LDX_MEM:
 536                 case BPF_S_ST:
 537                 case BPF_S_STX:
 538                         /* check for invalid memory addresses */
 539                         if (ftest->k >= BPF_MEMWORDS)
 540                                 return -EINVAL;
 541                         break;
 542                 case BPF_S_JMP_JA:
 543                         /*
 544                          * Note, the large ftest->k might cause loops.
 545                          * Compare this with conditional jumps below,
 546                          * where offsets are limited. --ANK (981016)
 547                          */
 548                         if (ftest->k >= (unsigned int)(flen-pc-1))
 549                                 return -EINVAL;
 550                         break;
 551                 case BPF_S_JMP_JEQ_K:
 552                 case BPF_S_JMP_JEQ_X:
 553                 case BPF_S_JMP_JGE_K:
 554                 case BPF_S_JMP_JGE_X:
 555                 case BPF_S_JMP_JGT_K:
 556                 case BPF_S_JMP_JGT_X:
 557                 case BPF_S_JMP_JSET_X:
 558                 case BPF_S_JMP_JSET_K:
 559                         /* for conditionals both must be safe */
 560                         if (pc + ftest->jt + 1 >= flen ||
 561                             pc + ftest->jf + 1 >= flen)
 562                                 return -EINVAL;
 563                         break;
 564                 case BPF_S_LD_W_ABS:
 565                 case BPF_S_LD_H_ABS:
 566                 case BPF_S_LD_B_ABS:
 567 #define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE:        \
 568                                 code = BPF_S_ANC_##CODE;        \
 569                                 break
 570                         switch (ftest->k) {
 571                         ANCILLARY(PROTOCOL);
 572                         ANCILLARY(PKTTYPE);
 573                         ANCILLARY(IFINDEX);
 574                         ANCILLARY(NLATTR);
 575                         ANCILLARY(NLATTR_NEST);
 576                         ANCILLARY(MARK);
 577                         ANCILLARY(QUEUE);
 578                         ANCILLARY(HATYPE);
 579                         ANCILLARY(RXHASH);
 580                         ANCILLARY(CPU);
 581                         ANCILLARY(ALU_XOR_X);
 582                         }
 583                 }
 584                 ftest->code = code;
 585         }
 586
 587         /* last instruction must be a RET code */
 588         switch (filter[flen - 1].code) {
 589         case BPF_S_RET_K:
 590         case BPF_S_RET_A:
 591                 return check_load_and_stores(filter, flen);
 592         }
 593         return -EINVAL;
 594 }
 595 EXPORT_SYMBOL(sk_chk_filter);
 596
 597 /**
 598  *      sk_filter_release_rcu - Release a socket filter by rcu_head
 599  *      @rcu: rcu_head that contains the sk_filter to free
 600  */
 601 void sk_filter_release_rcu(struct rcu_head *rcu)
 602 {
 603         struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
 604
 605         bpf_jit_free(fp);
 606         kfree(fp);
 607 }
 608 EXPORT_SYMBOL(sk_filter_release_rcu);
 609
 610 static int __sk_prepare_filter(struct sk_filter *fp)
 611 {
 612         int err;
 613
 614         fp->bpf_func = sk_run_filter;
 615
 616         err = sk_chk_filter(fp->insns, fp->len);
 617         if (err)
 618                 return err;
 619
 620         bpf_jit_compile(fp);
 621         return 0;
 622 }
 623
 624 /**
 625  *      sk_unattached_filter_create - create an unattached filter
 626  *      @fprog: the filter program
 627  *      @pfp: the unattached filter that is created
 628  *
 629  * Create a filter independent of any socket. We first run some
 630  * sanity checks on it to make sure it does not explode on us later.
 631  * If an error occurs or there is insufficient memory for the filter
 632  * a negative errno code is returned. On success the return is zero.
 633  */
 634 int sk_unattached_filter_create(struct sk_filter **pfp,
 635                                 struct sock_fprog *fprog)
 636 {
 637         struct sk_filter *fp;
 638         unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
 639         int err;
 640
 641         /* Make sure new filter is there and in the right amounts. */
 642         if (fprog->filter == NULL)
 643                 return -EINVAL;
 644
 645         fp = kmalloc(fsize + sizeof(*fp), GFP_KERNEL);
 646         if (!fp)
 647                 return -ENOMEM;
 648         memcpy(fp->insns, fprog->filter, fsize);
 649
 650         atomic_set(&fp->refcnt, 1);
 651         fp->len = fprog->len;
 652
 653         err = __sk_prepare_filter(fp);
 654         if (err)
 655                 goto free_mem;
 656
 657         *pfp = fp;
 658         return 0;
 659 free_mem:
 660         kfree(fp);
 661         return err;
 662 }
 663 EXPORT_SYMBOL_GPL(sk_unattached_filter_create);
 664
 665 void sk_unattached_filter_destroy(struct sk_filter *fp)
 666 {
 667         sk_filter_release(fp);
 668 }
 669 EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
 670
 671 /**
 672  *      sk_attach_filter - attach a socket filter
 673  *      @fprog: the filter program
 674  *      @sk: the socket to use
 675  *
 676  * Attach the user's filter code. We first run some sanity checks on
 677  * it to make sure it does not explode on us later. If an error
 678  * occurs or there is insufficient memory for the filter a negative
 679  * errno code is returned. On success the return is zero.
 680  */
 681 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 682 {
 683         struct sk_filter *fp, *old_fp;
 684         unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
 685         int err;
 686
 687         /* Make sure new filter is there and in the right amounts. */
 688         if (fprog->filter == NULL)
 689                 return -EINVAL;
 690
 691         fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
 692         if (!fp)
 693                 return -ENOMEM;
 694         if (copy_from_user(fp->insns, fprog->filter, fsize)) {
 695                 sock_kfree_s(sk, fp, fsize+sizeof(*fp));
 696                 return -EFAULT;
 697         }
 698
 699         atomic_set(&fp->refcnt, 1);
 700         fp->len = fprog->len;
 701
 702         err = __sk_prepare_filter(fp);
 703         if (err) {
 704                 sk_filter_uncharge(sk, fp);
 705                 return err;
 706         }
 707
 708         old_fp = rcu_dereference_protected(sk->sk_filter,
 709                                            sock_owned_by_user(sk));
 710         rcu_assign_pointer(sk->sk_filter, fp);
 711
 712         if (old_fp)
 713                 sk_filter_uncharge(sk, old_fp);
 714         return 0;
 715 }
 716 EXPORT_SYMBOL_GPL(sk_attach_filter);
 717
 718 int sk_detach_filter(struct sock *sk)
 719 {
 720         int ret = -ENOENT;
 721         struct sk_filter *filter;
 722
 723         filter = rcu_dereference_protected(sk->sk_filter,
 724                                            sock_owned_by_user(sk));
 725         if (filter) {
 726                 RCU_INIT_POINTER(sk->sk_filter, NULL);
 727                 sk_filter_uncharge(sk, filter);
 728                 ret = 0;
 729         }
 730         return ret;
 731 }
 732 EXPORT_SYMBOL_GPL(sk_detach_filter);