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 #include <linux/ratelimit.h>
  42
  43 enum {
  44         BPF_S_RET_K = 1,
  45         BPF_S_RET_A,
  46         BPF_S_ALU_ADD_K,
  47         BPF_S_ALU_ADD_X,
  48         BPF_S_ALU_SUB_K,
  49         BPF_S_ALU_SUB_X,
  50         BPF_S_ALU_MUL_K,
  51         BPF_S_ALU_MUL_X,
  52         BPF_S_ALU_DIV_X,
  53         BPF_S_ALU_AND_K,
  54         BPF_S_ALU_AND_X,
  55         BPF_S_ALU_OR_K,
  56         BPF_S_ALU_OR_X,
  57         BPF_S_ALU_LSH_K,
  58         BPF_S_ALU_LSH_X,
  59         BPF_S_ALU_RSH_K,
  60         BPF_S_ALU_RSH_X,
  61         BPF_S_ALU_NEG,
  62         BPF_S_LD_W_ABS,
  63         BPF_S_LD_H_ABS,
  64         BPF_S_LD_B_ABS,
  65         BPF_S_LD_W_LEN,
  66         BPF_S_LD_W_IND,
  67         BPF_S_LD_H_IND,
  68         BPF_S_LD_B_IND,
  69         BPF_S_LD_IMM,
  70         BPF_S_LDX_W_LEN,
  71         BPF_S_LDX_B_MSH,
  72         BPF_S_LDX_IMM,
  73         BPF_S_MISC_TAX,
  74         BPF_S_MISC_TXA,
  75         BPF_S_ALU_DIV_K,
  76         BPF_S_LD_MEM,
  77         BPF_S_LDX_MEM,
  78         BPF_S_ST,
  79         BPF_S_STX,
  80         BPF_S_JMP_JA,
  81         BPF_S_JMP_JEQ_K,
  82         BPF_S_JMP_JEQ_X,
  83         BPF_S_JMP_JGE_K,
  84         BPF_S_JMP_JGE_X,
  85         BPF_S_JMP_JGT_K,
  86         BPF_S_JMP_JGT_X,
  87         BPF_S_JMP_JSET_K,
  88         BPF_S_JMP_JSET_X,
  89         /* Ancillary data */
  90         BPF_S_ANC_PROTOCOL,
  91         BPF_S_ANC_PKTTYPE,
  92         BPF_S_ANC_IFINDEX,
  93         BPF_S_ANC_NLATTR,
  94         BPF_S_ANC_NLATTR_NEST,
  95         BPF_S_ANC_MARK,
  96         BPF_S_ANC_QUEUE,
  97         BPF_S_ANC_HATYPE,
  98         BPF_S_ANC_RXHASH,
  99         BPF_S_ANC_CPU,
 100 };
 101
 102 /* No hurry in this branch */
 103 static void *__load_pointer(const struct sk_buff *skb, int k, unsigned int size)
 104 {
 105         u8 *ptr = NULL;
 106
 107         if (k >= SKF_NET_OFF)
 108                 ptr = skb_network_header(skb) + k - SKF_NET_OFF;
 109         else if (k >= SKF_LL_OFF)
 110                 ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
 111
 112         if (ptr >= skb->head && ptr + size <= skb_tail_pointer(skb))
 113                 return ptr;
 114         return NULL;
 115 }
 116
 117 static inline void *load_pointer(const struct sk_buff *skb, int k,
 118                                  unsigned int size, void *buffer)
 119 {
 120         if (k >= 0)
 121                 return skb_header_pointer(skb, k, size, buffer);
 122         return __load_pointer(skb, k, size);
 123 }
 124
 125 /**
 126  *      sk_filter - run a packet through a socket filter
 127  *      @sk: sock associated with &sk_buff
 128  *      @skb: buffer to filter
 129  *
 130  * Run the filter code and then cut skb->data to correct size returned by
 131  * sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
 132  * than pkt_len we keep whole skb->data. This is the socket level
 133  * wrapper to sk_run_filter. It returns 0 if the packet should
 134  * be accepted or -EPERM if the packet should be tossed.
 135  *
 136  */
 137 int sk_filter(struct sock *sk, struct sk_buff *skb)
 138 {
 139         int err;
 140         struct sk_filter *filter;
 141
 142         err = security_sock_rcv_skb(sk, skb);
 143         if (err)
 144                 return err;
 145
 146         rcu_read_lock();
 147         filter = rcu_dereference(sk->sk_filter);
 148         if (filter) {
 149                 unsigned int pkt_len = sk_run_filter(skb, filter->insns);
 150
 151                 err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
 152         }
 153         rcu_read_unlock();
 154
 155         return err;
 156 }
 157 EXPORT_SYMBOL(sk_filter);
 158
 159 /**
 160  *      sk_run_filter - run a filter on a socket
 161  *      @skb: buffer to run the filter on
 162  *      @fentry: filter to apply
 163  *
 164  * Decode and apply filter instructions to the skb->data.
 165  * Return length to keep, 0 for none. @skb is the data we are
 166  * filtering, @filter is the array of filter instructions.
 167  * Because all jumps are guaranteed to be before last instruction,
 168  * and last instruction guaranteed to be a RET, we dont need to check
 169  * flen. (We used to pass to this function the length of filter)
 170  */
 171 unsigned int sk_run_filter(const struct sk_buff *skb,
 172                            const struct sock_filter *fentry)
 173 {
 174         void *ptr;
 175         u32 A = 0;                      /* Accumulator */
 176         u32 X = 0;                      /* Index Register */
 177         u32 mem[BPF_MEMWORDS];          /* Scratch Memory Store */
 178         u32 tmp;
 179         int k;
 180
 181         /*
 182          * Process array of filter instructions.
 183          */
 184         for (;; fentry++) {
 185 #if defined(CONFIG_X86_32)
 186 #define K (fentry->k)
 187 #else
 188                 const u32 K = fentry->k;
 189 #endif
 190
 191                 switch (fentry->code) {
 192                 case BPF_S_ALU_ADD_X:
 193                         A += X;
 194                         continue;
 195                 case BPF_S_ALU_ADD_K:
 196                         A += K;
 197                         continue;
 198                 case BPF_S_ALU_SUB_X:
 199                         A -= X;
 200                         continue;
 201                 case BPF_S_ALU_SUB_K:
 202                         A -= K;
 203                         continue;
 204                 case BPF_S_ALU_MUL_X:
 205                         A *= X;
 206                         continue;
 207                 case BPF_S_ALU_MUL_K:
 208                         A *= K;
 209                         continue;
 210                 case BPF_S_ALU_DIV_X:
 211                         if (X == 0)
 212                                 return 0;
 213                         A /= X;
 214                         continue;
 215                 case BPF_S_ALU_DIV_K:
 216                         A = reciprocal_divide(A, K);
 217                         continue;
 218                 case BPF_S_ALU_AND_X:
 219                         A &= X;
 220                         continue;
 221                 case BPF_S_ALU_AND_K:
 222                         A &= K;
 223                         continue;
 224                 case BPF_S_ALU_OR_X:
 225                         A |= X;
 226                         continue;
 227                 case BPF_S_ALU_OR_K:
 228                         A |= K;
 229                         continue;
 230                 case BPF_S_ALU_LSH_X:
 231                         A <<= X;
 232                         continue;
 233                 case BPF_S_ALU_LSH_K:
 234                         A <<= K;
 235                         continue;
 236                 case BPF_S_ALU_RSH_X:
 237                         A >>= X;
 238                         continue;
 239                 case BPF_S_ALU_RSH_K:
 240                         A >>= K;
 241                         continue;
 242                 case BPF_S_ALU_NEG:
 243                         A = -A;
 244                         continue;
 245                 case BPF_S_JMP_JA:
 246                         fentry += K;
 247                         continue;
 248                 case BPF_S_JMP_JGT_K:
 249                         fentry += (A > K) ? fentry->jt : fentry->jf;
 250                         continue;
 251                 case BPF_S_JMP_JGE_K:
 252                         fentry += (A >= K) ? fentry->jt : fentry->jf;
 253                         continue;
 254                 case BPF_S_JMP_JEQ_K:
 255                         fentry += (A == K) ? fentry->jt : fentry->jf;
 256                         continue;
 257                 case BPF_S_JMP_JSET_K:
 258                         fentry += (A & K) ? fentry->jt : fentry->jf;
 259                         continue;
 260                 case BPF_S_JMP_JGT_X:
 261                         fentry += (A > X) ? fentry->jt : fentry->jf;
 262                         continue;
 263                 case BPF_S_JMP_JGE_X:
 264                         fentry += (A >= X) ? fentry->jt : fentry->jf;
 265                         continue;
 266                 case BPF_S_JMP_JEQ_X:
 267                         fentry += (A == X) ? fentry->jt : fentry->jf;
 268                         continue;
 269                 case BPF_S_JMP_JSET_X:
 270                         fentry += (A & X) ? fentry->jt : fentry->jf;
 271                         continue;
 272                 case BPF_S_LD_W_ABS:
 273                         k = K;
 274 load_w:
 275                         ptr = load_pointer(skb, k, 4, &tmp);
 276                         if (ptr != NULL) {
 277                                 A = get_unaligned_be32(ptr);
 278                                 continue;
 279                         }
 280                         return 0;
 281                 case BPF_S_LD_H_ABS:
 282                         k = K;
 283 load_h:
 284                         ptr = load_pointer(skb, k, 2, &tmp);
 285                         if (ptr != NULL) {
 286                                 A = get_unaligned_be16(ptr);
 287                                 continue;
 288                         }
 289                         return 0;
 290                 case BPF_S_LD_B_ABS:
 291                         k = K;
 292 load_b:
 293                         ptr = load_pointer(skb, k, 1, &tmp);
 294                         if (ptr != NULL) {
 295                                 A = *(u8 *)ptr;
 296                                 continue;
 297                         }
 298                         return 0;
 299                 case BPF_S_LD_W_LEN:
 300                         A = skb->len;
 301                         continue;
 302                 case BPF_S_LDX_W_LEN:
 303                         X = skb->len;
 304                         continue;
 305                 case BPF_S_LD_W_IND:
 306                         k = X + K;
 307                         goto load_w;
 308                 case BPF_S_LD_H_IND:
 309                         k = X + K;
 310                         goto load_h;
 311                 case BPF_S_LD_B_IND:
 312                         k = X + K;
 313                         goto load_b;
 314                 case BPF_S_LDX_B_MSH:
 315                         ptr = load_pointer(skb, K, 1, &tmp);
 316                         if (ptr != NULL) {
 317                                 X = (*(u8 *)ptr & 0xf) << 2;
 318                                 continue;
 319                         }
 320                         return 0;
 321                 case BPF_S_LD_IMM:
 322                         A = K;
 323                         continue;
 324                 case BPF_S_LDX_IMM:
 325                         X = K;
 326                         continue;
 327                 case BPF_S_LD_MEM:
 328                         A = mem[K];
 329                         continue;
 330                 case BPF_S_LDX_MEM:
 331                         X = mem[K];
 332                         continue;
 333                 case BPF_S_MISC_TAX:
 334                         X = A;
 335                         continue;
 336                 case BPF_S_MISC_TXA:
 337                         A = X;
 338                         continue;
 339                 case BPF_S_RET_K:
 340                         return K;
 341                 case BPF_S_RET_A:
 342                         return A;
 343                 case BPF_S_ST:
 344                         mem[K] = A;
 345                         continue;
 346                 case BPF_S_STX:
 347                         mem[K] = X;
 348                         continue;
 349                 case BPF_S_ANC_PROTOCOL:
 350                         A = ntohs(skb->protocol);
 351                         continue;
 352                 case BPF_S_ANC_PKTTYPE:
 353                         A = skb->pkt_type;
 354                         continue;
 355                 case BPF_S_ANC_IFINDEX:
 356                         if (!skb->dev)
 357                                 return 0;
 358                         A = skb->dev->ifindex;
 359                         continue;
 360                 case BPF_S_ANC_MARK:
 361                         A = skb->mark;
 362                         continue;
 363                 case BPF_S_ANC_QUEUE:
 364                         A = skb->queue_mapping;
 365                         continue;
 366                 case BPF_S_ANC_HATYPE:
 367                         if (!skb->dev)
 368                                 return 0;
 369                         A = skb->dev->type;
 370                         continue;
 371                 case BPF_S_ANC_RXHASH:
 372                         A = skb->rxhash;
 373                         continue;
 374                 case BPF_S_ANC_CPU:
 375                         A = raw_smp_processor_id();
 376                         continue;
 377                 case BPF_S_ANC_NLATTR: {
 378                         struct nlattr *nla;
 379
 380                         if (skb_is_nonlinear(skb))
 381                                 return 0;
 382                         if (A > skb->len - sizeof(struct nlattr))
 383                                 return 0;
 384
 385                         nla = nla_find((struct nlattr *)&skb->data[A],
 386                                        skb->len - A, X);
 387                         if (nla)
 388                                 A = (void *)nla - (void *)skb->data;
 389                         else
 390                                 A = 0;
 391                         continue;
 392                 }
 393                 case BPF_S_ANC_NLATTR_NEST: {
 394                         struct nlattr *nla;
 395
 396                         if (skb_is_nonlinear(skb))
 397                                 return 0;
 398                         if (A > skb->len - sizeof(struct nlattr))
 399                                 return 0;
 400
 401                         nla = (struct nlattr *)&skb->data[A];
 402                         if (nla->nla_len > A - skb->len)
 403                                 return 0;
 404
 405                         nla = nla_find_nested(nla, X);
 406                         if (nla)
 407                                 A = (void *)nla - (void *)skb->data;
 408                         else
 409                                 A = 0;
 410                         continue;
 411                 }
 412                 default:
 413                         WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
 414                                        fentry->code, fentry->jt,
 415                                        fentry->jf, fentry->k);
 416                         return 0;
 417                 }
 418         }
 419
 420         return 0;
 421 }
 422 EXPORT_SYMBOL(sk_run_filter);
 423
 424 /*
 425  * Security :
 426  * A BPF program is able to use 16 cells of memory to store intermediate
 427  * values (check u32 mem[BPF_MEMWORDS] in sk_run_filter())
 428  * As we dont want to clear mem[] array for each packet going through
 429  * sk_run_filter(), we check that filter loaded by user never try to read
 430  * a cell if not previously written, and we check all branches to be sure
 431  * a malicious user doesn't try to abuse us.
 432  */
 433 static int check_load_and_stores(struct sock_filter *filter, int flen)
 434 {
 435         u16 *masks, memvalid = 0; /* one bit per cell, 16 cells */
 436         int pc, ret = 0;
 437
 438         BUILD_BUG_ON(BPF_MEMWORDS > 16);
 439         masks = kmalloc(flen * sizeof(*masks), GFP_KERNEL);
 440         if (!masks)
 441                 return -ENOMEM;
 442         memset(masks, 0xff, flen * sizeof(*masks));
 443
 444         for (pc = 0; pc < flen; pc++) {
 445                 memvalid &= masks[pc];
 446
 447                 switch (filter[pc].code) {
 448                 case BPF_S_ST:
 449                 case BPF_S_STX:
 450                         memvalid |= (1 << filter[pc].k);
 451                         break;
 452                 case BPF_S_LD_MEM:
 453                 case BPF_S_LDX_MEM:
 454                         if (!(memvalid & (1 << filter[pc].k))) {
 455                                 ret = -EINVAL;
 456                                 goto error;
 457                         }
 458                         break;
 459                 case BPF_S_JMP_JA:
 460                         /* a jump must set masks on target */
 461                         masks[pc + 1 + filter[pc].k] &= memvalid;
 462                         memvalid = ~0;
 463                         break;
 464                 case BPF_S_JMP_JEQ_K:
 465                 case BPF_S_JMP_JEQ_X:
 466                 case BPF_S_JMP_JGE_K:
 467                 case BPF_S_JMP_JGE_X:
 468                 case BPF_S_JMP_JGT_K:
 469                 case BPF_S_JMP_JGT_X:
 470                 case BPF_S_JMP_JSET_X:
 471                 case BPF_S_JMP_JSET_K:
 472                         /* a jump must set masks on targets */
 473                         masks[pc + 1 + filter[pc].jt] &= memvalid;
 474                         masks[pc + 1 + filter[pc].jf] &= memvalid;
 475                         memvalid = ~0;
 476                         break;
 477                 }
 478         }
 479 error:
 480         kfree(masks);
 481         return ret;
 482 }
 483
 484 /**
 485  *      sk_chk_filter - verify socket filter code
 486  *      @filter: filter to verify
 487  *      @flen: length of filter
 488  *
 489  * Check the user's filter code. If we let some ugly
 490  * filter code slip through kaboom! The filter must contain
 491  * no references or jumps that are out of range, no illegal
 492  * instructions, and must end with a RET instruction.
 493  *
 494  * All jumps are forward as they are not signed.
 495  *
 496  * Returns 0 if the rule set is legal or -EINVAL if not.
 497  */
 498 int sk_chk_filter(struct sock_filter *filter, int flen)
 499 {
 500         /*
 501          * Valid instructions are initialized to non-0.
 502          * Invalid instructions are initialized to 0.
 503          */
 504         static const u8 codes[] = {
 505                 [BPF_ALU|BPF_ADD|BPF_K]  = BPF_S_ALU_ADD_K,
 506                 [BPF_ALU|BPF_ADD|BPF_X]  = BPF_S_ALU_ADD_X,
 507                 [BPF_ALU|BPF_SUB|BPF_K]  = BPF_S_ALU_SUB_K,
 508                 [BPF_ALU|BPF_SUB|BPF_X]  = BPF_S_ALU_SUB_X,
 509                 [BPF_ALU|BPF_MUL|BPF_K]  = BPF_S_ALU_MUL_K,
 510                 [BPF_ALU|BPF_MUL|BPF_X]  = BPF_S_ALU_MUL_X,
 511                 [BPF_ALU|BPF_DIV|BPF_X]  = BPF_S_ALU_DIV_X,
 512                 [BPF_ALU|BPF_AND|BPF_K]  = BPF_S_ALU_AND_K,
 513                 [BPF_ALU|BPF_AND|BPF_X]  = BPF_S_ALU_AND_X,
 514                 [BPF_ALU|BPF_OR|BPF_K]   = BPF_S_ALU_OR_K,
 515                 [BPF_ALU|BPF_OR|BPF_X]   = BPF_S_ALU_OR_X,
 516                 [BPF_ALU|BPF_LSH|BPF_K]  = BPF_S_ALU_LSH_K,
 517                 [BPF_ALU|BPF_LSH|BPF_X]  = BPF_S_ALU_LSH_X,
 518                 [BPF_ALU|BPF_RSH|BPF_K]  = BPF_S_ALU_RSH_K,
 519                 [BPF_ALU|BPF_RSH|BPF_X]  = BPF_S_ALU_RSH_X,
 520                 [BPF_ALU|BPF_NEG]        = BPF_S_ALU_NEG,
 521                 [BPF_LD|BPF_W|BPF_ABS]   = BPF_S_LD_W_ABS,
 522                 [BPF_LD|BPF_H|BPF_ABS]   = BPF_S_LD_H_ABS,
 523                 [BPF_LD|BPF_B|BPF_ABS]   = BPF_S_LD_B_ABS,
 524                 [BPF_LD|BPF_W|BPF_LEN]   = BPF_S_LD_W_LEN,
 525                 [BPF_LD|BPF_W|BPF_IND]   = BPF_S_LD_W_IND,
 526                 [BPF_LD|BPF_H|BPF_IND]   = BPF_S_LD_H_IND,
 527                 [BPF_LD|BPF_B|BPF_IND]   = BPF_S_LD_B_IND,
 528                 [BPF_LD|BPF_IMM]         = BPF_S_LD_IMM,
 529                 [BPF_LDX|BPF_W|BPF_LEN]  = BPF_S_LDX_W_LEN,
 530                 [BPF_LDX|BPF_B|BPF_MSH]  = BPF_S_LDX_B_MSH,
 531                 [BPF_LDX|BPF_IMM]        = BPF_S_LDX_IMM,
 532                 [BPF_MISC|BPF_TAX]       = BPF_S_MISC_TAX,
 533                 [BPF_MISC|BPF_TXA]       = BPF_S_MISC_TXA,
 534                 [BPF_RET|BPF_K]          = BPF_S_RET_K,
 535                 [BPF_RET|BPF_A]          = BPF_S_RET_A,
 536                 [BPF_ALU|BPF_DIV|BPF_K]  = BPF_S_ALU_DIV_K,
 537                 [BPF_LD|BPF_MEM]         = BPF_S_LD_MEM,
 538                 [BPF_LDX|BPF_MEM]        = BPF_S_LDX_MEM,
 539                 [BPF_ST]                 = BPF_S_ST,
 540                 [BPF_STX]                = BPF_S_STX,
 541                 [BPF_JMP|BPF_JA]         = BPF_S_JMP_JA,
 542                 [BPF_JMP|BPF_JEQ|BPF_K]  = BPF_S_JMP_JEQ_K,
 543                 [BPF_JMP|BPF_JEQ|BPF_X]  = BPF_S_JMP_JEQ_X,
 544                 [BPF_JMP|BPF_JGE|BPF_K]  = BPF_S_JMP_JGE_K,
 545                 [BPF_JMP|BPF_JGE|BPF_X]  = BPF_S_JMP_JGE_X,
 546                 [BPF_JMP|BPF_JGT|BPF_K]  = BPF_S_JMP_JGT_K,
 547                 [BPF_JMP|BPF_JGT|BPF_X]  = BPF_S_JMP_JGT_X,
 548                 [BPF_JMP|BPF_JSET|BPF_K] = BPF_S_JMP_JSET_K,
 549                 [BPF_JMP|BPF_JSET|BPF_X] = BPF_S_JMP_JSET_X,
 550         };
 551         int pc;
 552
 553         if (flen == 0 || flen > BPF_MAXINSNS)
 554                 return -EINVAL;
 555
 556         /* check the filter code now */
 557         for (pc = 0; pc < flen; pc++) {
 558                 struct sock_filter *ftest = &filter[pc];
 559                 u16 code = ftest->code;
 560
 561                 if (code >= ARRAY_SIZE(codes))
 562                         return -EINVAL;
 563                 code = codes[code];
 564                 if (!code)
 565                         return -EINVAL;
 566                 /* Some instructions need special checks */
 567                 switch (code) {
 568                 case BPF_S_ALU_DIV_K:
 569                         /* check for division by zero */
 570                         if (ftest->k == 0)
 571                                 return -EINVAL;
 572                         ftest->k = reciprocal_value(ftest->k);
 573                         break;
 574                 case BPF_S_LD_MEM:
 575                 case BPF_S_LDX_MEM:
 576                 case BPF_S_ST:
 577                 case BPF_S_STX:
 578                         /* check for invalid memory addresses */
 579                         if (ftest->k >= BPF_MEMWORDS)
 580                                 return -EINVAL;
 581                         break;
 582                 case BPF_S_JMP_JA:
 583                         /*
 584                          * Note, the large ftest->k might cause loops.
 585                          * Compare this with conditional jumps below,
 586                          * where offsets are limited. --ANK (981016)
 587                          */
 588                         if (ftest->k >= (unsigned)(flen-pc-1))
 589                                 return -EINVAL;
 590                         break;
 591                 case BPF_S_JMP_JEQ_K:
 592                 case BPF_S_JMP_JEQ_X:
 593                 case BPF_S_JMP_JGE_K:
 594                 case BPF_S_JMP_JGE_X:
 595                 case BPF_S_JMP_JGT_K:
 596                 case BPF_S_JMP_JGT_X:
 597                 case BPF_S_JMP_JSET_X:
 598                 case BPF_S_JMP_JSET_K:
 599                         /* for conditionals both must be safe */
 600                         if (pc + ftest->jt + 1 >= flen ||
 601                             pc + ftest->jf + 1 >= flen)
 602                                 return -EINVAL;
 603                         break;
 604                 case BPF_S_LD_W_ABS:
 605                 case BPF_S_LD_H_ABS:
 606                 case BPF_S_LD_B_ABS:
 607 #define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE:        \
 608                                 code = BPF_S_ANC_##CODE;        \
 609                                 break
 610                         switch (ftest->k) {
 611                         ANCILLARY(PROTOCOL);
 612                         ANCILLARY(PKTTYPE);
 613                         ANCILLARY(IFINDEX);
 614                         ANCILLARY(NLATTR);
 615                         ANCILLARY(NLATTR_NEST);
 616                         ANCILLARY(MARK);
 617                         ANCILLARY(QUEUE);
 618                         ANCILLARY(HATYPE);
 619                         ANCILLARY(RXHASH);
 620                         ANCILLARY(CPU);
 621                         }
 622                 }
 623                 ftest->code = code;
 624         }
 625
 626         /* last instruction must be a RET code */
 627         switch (filter[flen - 1].code) {
 628         case BPF_S_RET_K:
 629         case BPF_S_RET_A:
 630                 return check_load_and_stores(filter, flen);
 631         }
 632         return -EINVAL;
 633 }
 634 EXPORT_SYMBOL(sk_chk_filter);
 635
 636 /**
 637  *      sk_filter_release_rcu - Release a socket filter by rcu_head
 638  *      @rcu: rcu_head that contains the sk_filter to free
 639  */
 640 void sk_filter_release_rcu(struct rcu_head *rcu)
 641 {
 642         struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
 643
 644         kfree(fp);
 645 }
 646 EXPORT_SYMBOL(sk_filter_release_rcu);
 647
 648 /**
 649  *      sk_attach_filter - attach a socket filter
 650  *      @fprog: the filter program
 651  *      @sk: the socket to use
 652  *
 653  * Attach the user's filter code. We first run some sanity checks on
 654  * it to make sure it does not explode on us later. If an error
 655  * occurs or there is insufficient memory for the filter a negative
 656  * errno code is returned. On success the return is zero.
 657  */
 658 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 659 {
 660         struct sk_filter *fp, *old_fp;
 661         unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
 662         int err;
 663
 664         /* Make sure new filter is there and in the right amounts. */
 665         if (fprog->filter == NULL)
 666                 return -EINVAL;
 667
 668         fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
 669         if (!fp)
 670                 return -ENOMEM;
 671         if (copy_from_user(fp->insns, fprog->filter, fsize)) {
 672                 sock_kfree_s(sk, fp, fsize+sizeof(*fp));
 673                 return -EFAULT;
 674         }
 675
 676         atomic_set(&fp->refcnt, 1);
 677         fp->len = fprog->len;
 678
 679         err = sk_chk_filter(fp->insns, fp->len);
 680         if (err) {
 681                 sk_filter_uncharge(sk, fp);
 682                 return err;
 683         }
 684
 685         old_fp = rcu_dereference_protected(sk->sk_filter,
 686                                            sock_owned_by_user(sk));
 687         rcu_assign_pointer(sk->sk_filter, fp);
 688
 689         if (old_fp)
 690                 sk_filter_uncharge(sk, old_fp);
 691         return 0;
 692 }
 693 EXPORT_SYMBOL_GPL(sk_attach_filter);
 694
 695 int sk_detach_filter(struct sock *sk)
 696 {
 697         int ret = -ENOENT;
 698         struct sk_filter *filter;
 699
 700         filter = rcu_dereference_protected(sk->sk_filter,
 701                                            sock_owned_by_user(sk));
 702         if (filter) {
 703                 rcu_assign_pointer(sk->sk_filter, NULL);
 704                 sk_filter_uncharge(sk, filter);
 705                 ret = 0;
 706         }
 707         return ret;
 708 }
 709 EXPORT_SYMBOL_GPL(sk_detach_filter);