SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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  */
  17
  18 #include <linux/module.h>
  19 #include <linux/types.h>
  20 #include <linux/sched.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 <net/ip.h>
  29 #include <net/protocol.h>
  30 #include <linux/skbuff.h>
  31 #include <net/sock.h>
  32 #include <linux/errno.h>
  33 #include <linux/timer.h>
  34 #include <asm/system.h>
  35 #include <asm/uaccess.h>
  36 #include <linux/filter.h>
  37
  38 /* No hurry in this branch */
  39 static void *__load_pointer(struct sk_buff *skb, int k)
  40 {
  41         u8 *ptr = NULL;
  42
  43         if (k >= SKF_NET_OFF)
  44                 ptr = skb->nh.raw + k - SKF_NET_OFF;
  45         else if (k >= SKF_LL_OFF)
  46                 ptr = skb->mac.raw + k - SKF_LL_OFF;
  47
  48         if (ptr >= skb->head && ptr < skb->tail)
  49                 return ptr;
  50         return NULL;
  51 }
  52
  53 static inline void *load_pointer(struct sk_buff *skb, int k,
  54                                  unsigned int size, void *buffer)
  55 {
  56         if (k >= 0)
  57                 return skb_header_pointer(skb, k, size, buffer);
  58         else {
  59                 if (k >= SKF_AD_OFF)
  60                         return NULL;
  61                 return __load_pointer(skb, k);
  62         }
  63 }
  64
  65 /**
  66  *      sk_run_filter   -       run a filter on a socket
  67  *      @skb: buffer to run the filter on
  68  *      @filter: filter to apply
  69  *      @flen: length of filter
  70  *
  71  * Decode and apply filter instructions to the skb->data.
  72  * Return length to keep, 0 for none. skb is the data we are
  73  * filtering, filter is the array of filter instructions, and
  74  * len is the number of filter blocks in the array.
  75  */
  76
  77 int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen)
  78 {
  79         struct sock_filter *fentry;     /* We walk down these */
  80         void *ptr;
  81         u32 A = 0;                      /* Accumulator */
  82         u32 X = 0;                      /* Index Register */
  83         u32 mem[BPF_MEMWORDS];          /* Scratch Memory Store */
  84         u32 tmp;
  85         int k;
  86         int pc;
  87
  88         /*
  89          * Process array of filter instructions.
  90          */
  91         for (pc = 0; pc < flen; pc++) {
  92                 fentry = &filter[pc];
  93
  94                 switch (fentry->code) {
  95                 case BPF_ALU|BPF_ADD|BPF_X:
  96                         A += X;
  97                         continue;
  98                 case BPF_ALU|BPF_ADD|BPF_K:
  99                         A += fentry->k;
 100                         continue;
 101                 case BPF_ALU|BPF_SUB|BPF_X:
 102                         A -= X;
 103                         continue;
 104                 case BPF_ALU|BPF_SUB|BPF_K:
 105                         A -= fentry->k;
 106                         continue;
 107                 case BPF_ALU|BPF_MUL|BPF_X:
 108                         A *= X;
 109                         continue;
 110                 case BPF_ALU|BPF_MUL|BPF_K:
 111                         A *= fentry->k;
 112                         continue;
 113                 case BPF_ALU|BPF_DIV|BPF_X:
 114                         if (X == 0)
 115                                 return 0;
 116                         A /= X;
 117                         continue;
 118                 case BPF_ALU|BPF_DIV|BPF_K:
 119                         A /= fentry->k;
 120                         continue;
 121                 case BPF_ALU|BPF_AND|BPF_X:
 122                         A &= X;
 123                         continue;
 124                 case BPF_ALU|BPF_AND|BPF_K:
 125                         A &= fentry->k;
 126                         continue;
 127                 case BPF_ALU|BPF_OR|BPF_X:
 128                         A |= X;
 129                         continue;
 130                 case BPF_ALU|BPF_OR|BPF_K:
 131                         A |= fentry->k;
 132                         continue;
 133                 case BPF_ALU|BPF_LSH|BPF_X:
 134                         A <<= X;
 135                         continue;
 136                 case BPF_ALU|BPF_LSH|BPF_K:
 137                         A <<= fentry->k;
 138                         continue;
 139                 case BPF_ALU|BPF_RSH|BPF_X:
 140                         A >>= X;
 141                         continue;
 142                 case BPF_ALU|BPF_RSH|BPF_K:
 143                         A >>= fentry->k;
 144                         continue;
 145                 case BPF_ALU|BPF_NEG:
 146                         A = -A;
 147                         continue;
 148                 case BPF_JMP|BPF_JA:
 149                         pc += fentry->k;
 150                         continue;
 151                 case BPF_JMP|BPF_JGT|BPF_K:
 152                         pc += (A > fentry->k) ? fentry->jt : fentry->jf;
 153                         continue;
 154                 case BPF_JMP|BPF_JGE|BPF_K:
 155                         pc += (A >= fentry->k) ? fentry->jt : fentry->jf;
 156                         continue;
 157                 case BPF_JMP|BPF_JEQ|BPF_K:
 158                         pc += (A == fentry->k) ? fentry->jt : fentry->jf;
 159                         continue;
 160                 case BPF_JMP|BPF_JSET|BPF_K:
 161                         pc += (A & fentry->k) ? fentry->jt : fentry->jf;
 162                         continue;
 163                 case BPF_JMP|BPF_JGT|BPF_X:
 164                         pc += (A > X) ? fentry->jt : fentry->jf;
 165                         continue;
 166                 case BPF_JMP|BPF_JGE|BPF_X:
 167                         pc += (A >= X) ? fentry->jt : fentry->jf;
 168                         continue;
 169                 case BPF_JMP|BPF_JEQ|BPF_X:
 170                         pc += (A == X) ? fentry->jt : fentry->jf;
 171                         continue;
 172                 case BPF_JMP|BPF_JSET|BPF_X:
 173                         pc += (A & X) ? fentry->jt : fentry->jf;
 174                         continue;
 175                 case BPF_LD|BPF_W|BPF_ABS:
 176                         k = fentry->k;
 177  load_w:
 178                         ptr = load_pointer(skb, k, 4, &tmp);
 179                         if (ptr != NULL) {
 180                                 A = ntohl(*(u32 *)ptr);
 181                                 continue;
 182                         }
 183                         break;
 184                 case BPF_LD|BPF_H|BPF_ABS:
 185                         k = fentry->k;
 186  load_h:
 187                         ptr = load_pointer(skb, k, 2, &tmp);
 188                         if (ptr != NULL) {
 189                                 A = ntohs(*(u16 *)ptr);
 190                                 continue;
 191                         }
 192                         break;
 193                 case BPF_LD|BPF_B|BPF_ABS:
 194                         k = fentry->k;
 195 load_b:
 196                         ptr = load_pointer(skb, k, 1, &tmp);
 197                         if (ptr != NULL) {
 198                                 A = *(u8 *)ptr;
 199                                 continue;
 200                         }
 201                         break;
 202                 case BPF_LD|BPF_W|BPF_LEN:
 203                         A = skb->len;
 204                         continue;
 205                 case BPF_LDX|BPF_W|BPF_LEN:
 206                         X = skb->len;
 207                         continue;
 208                 case BPF_LD|BPF_W|BPF_IND:
 209                         k = X + fentry->k;
 210                         goto load_w;
 211                 case BPF_LD|BPF_H|BPF_IND:
 212                         k = X + fentry->k;
 213                         goto load_h;
 214                 case BPF_LD|BPF_B|BPF_IND:
 215                         k = X + fentry->k;
 216                         goto load_b;
 217                 case BPF_LDX|BPF_B|BPF_MSH:
 218                         ptr = load_pointer(skb, fentry->k, 1, &tmp);
 219                         if (ptr != NULL) {
 220                                 X = (*(u8 *)ptr & 0xf) << 2;
 221                                 continue;
 222                         }
 223                         return 0;
 224                 case BPF_LD|BPF_IMM:
 225                         A = fentry->k;
 226                         continue;
 227                 case BPF_LDX|BPF_IMM:
 228                         X = fentry->k;
 229                         continue;
 230                 case BPF_LD|BPF_MEM:
 231                         A = mem[fentry->k];
 232                         continue;
 233                 case BPF_LDX|BPF_MEM:
 234                         X = mem[fentry->k];
 235                         continue;
 236                 case BPF_MISC|BPF_TAX:
 237                         X = A;
 238                         continue;
 239                 case BPF_MISC|BPF_TXA:
 240                         A = X;
 241                         continue;
 242                 case BPF_RET|BPF_K:
 243                         return ((unsigned int)fentry->k);
 244                 case BPF_RET|BPF_A:
 245                         return ((unsigned int)A);
 246                 case BPF_ST:
 247                         mem[fentry->k] = A;
 248                         continue;
 249                 case BPF_STX:
 250                         mem[fentry->k] = X;
 251                         continue;
 252                 default:
 253                         /* Invalid instruction counts as RET */
 254                         return 0;
 255                 }
 256
 257                 /*
 258                  * Handle ancillary data, which are impossible
 259                  * (or very difficult) to get parsing packet contents.
 260                  */
 261                 switch (k-SKF_AD_OFF) {
 262                 case SKF_AD_PROTOCOL:
 263                         A = htons(skb->protocol);
 264                         continue;
 265                 case SKF_AD_PKTTYPE:
 266                         A = skb->pkt_type;
 267                         continue;
 268                 case SKF_AD_IFINDEX:
 269                         A = skb->dev->ifindex;
 270                         continue;
 271                 default:
 272                         return 0;
 273                 }
 274         }
 275
 276         return 0;
 277 }
 278
 279 /**
 280  *      sk_chk_filter - verify socket filter code
 281  *      @filter: filter to verify
 282  *      @flen: length of filter
 283  *
 284  * Check the user's filter code. If we let some ugly
 285  * filter code slip through kaboom! The filter must contain
 286  * no references or jumps that are out of range, no illegal instructions
 287  * and no backward jumps. It must end with a RET instruction
 288  *
 289  * Returns 0 if the rule set is legal or a negative errno code if not.
 290  */
 291 int sk_chk_filter(struct sock_filter *filter, int flen)
 292 {
 293         struct sock_filter *ftest;
 294         int pc;
 295
 296         if (flen == 0 || flen > BPF_MAXINSNS)
 297                 return -EINVAL;
 298
 299         /* check the filter code now */
 300         for (pc = 0; pc < flen; pc++) {
 301                 /* all jumps are forward as they are not signed */
 302                 ftest = &filter[pc];
 303                 if (BPF_CLASS(ftest->code) == BPF_JMP) {
 304                         /* but they mustn't jump off the end */
 305                         if (BPF_OP(ftest->code) == BPF_JA) {
 306                                 /*
 307                                  * Note, the large ftest->k might cause loops.
 308                                  * Compare this with conditional jumps below,
 309                                  * where offsets are limited. --ANK (981016)
 310                                  */
 311                                 if (ftest->k >= (unsigned)(flen-pc-1))
 312                                         return -EINVAL;
 313                         } else {
 314                                 /* for conditionals both must be safe */
 315                                 if (pc + ftest->jt +1 >= flen ||
 316                                     pc + ftest->jf +1 >= flen)
 317                                         return -EINVAL;
 318                         }
 319                 }
 320
 321                 /* check for division by zero   -Kris Katterjohn 2005-10-30 */
 322                 if (ftest->code == (BPF_ALU|BPF_DIV|BPF_K) && ftest->k == 0)
 323                         return -EINVAL;
 324
 325                 /* check that memory operations use valid addresses. */
 326                 if (ftest->k >= BPF_MEMWORDS) {
 327                         /* but it might not be a memory operation... */
 328                         switch (ftest->code) {
 329                         case BPF_ST:
 330                         case BPF_STX:
 331                         case BPF_LD|BPF_MEM:
 332                         case BPF_LDX|BPF_MEM:
 333                                 return -EINVAL;
 334                         }
 335                 }
 336         }
 337
 338         /*
 339          * The program must end with a return. We don't care where they
 340          * jumped within the script (its always forwards) but in the end
 341          * they _will_ hit this.
 342          */
 343         return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL;
 344 }
 345
 346 /**
 347  *      sk_attach_filter - attach a socket filter
 348  *      @fprog: the filter program
 349  *      @sk: the socket to use
 350  *
 351  * Attach the user's filter code. We first run some sanity checks on
 352  * it to make sure it does not explode on us later. If an error
 353  * occurs or there is insufficient memory for the filter a negative
 354  * errno code is returned. On success the return is zero.
 355  */
 356 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 357 {
 358         struct sk_filter *fp;
 359         unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
 360         int err;
 361
 362         /* Make sure new filter is there and in the right amounts. */
 363         if (fprog->filter == NULL)
 364                 return -EINVAL;
 365
 366         fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
 367         if (!fp)
 368                 return -ENOMEM;
 369         if (copy_from_user(fp->insns, fprog->filter, fsize)) {
 370                 sock_kfree_s(sk, fp, fsize+sizeof(*fp));
 371                 return -EFAULT;
 372         }
 373
 374         atomic_set(&fp->refcnt, 1);
 375         fp->len = fprog->len;
 376
 377         err = sk_chk_filter(fp->insns, fp->len);
 378         if (!err) {
 379                 struct sk_filter *old_fp;
 380
 381                 spin_lock_bh(&sk->sk_lock.slock);
 382                 old_fp = sk->sk_filter;
 383                 sk->sk_filter = fp;
 384                 spin_unlock_bh(&sk->sk_lock.slock);
 385                 fp = old_fp;
 386         }
 387
 388         if (fp)
 389                 sk_filter_release(sk, fp);
 390         return err;
 391 }
 392
 393 EXPORT_SYMBOL(sk_chk_filter);
 394 EXPORT_SYMBOL(sk_run_filter);