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1da177e4 LT |
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. | |
93699863 | 16 | * Kris Katterjohn - Added many additional checks in sk_chk_filter() |
1da177e4 LT |
17 | */ |
18 | ||
19 | #include <linux/module.h> | |
20 | #include <linux/types.h> | |
1da177e4 LT |
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> | |
40daafc8 | 36 | #include <asm/unaligned.h> |
1da177e4 LT |
37 | #include <linux/filter.h> |
38 | ||
39 | /* No hurry in this branch */ | |
0b05b2a4 | 40 | static void *__load_pointer(struct sk_buff *skb, int k) |
1da177e4 LT |
41 | { |
42 | u8 *ptr = NULL; | |
43 | ||
44 | if (k >= SKF_NET_OFF) | |
45 | ptr = skb->nh.raw + k - SKF_NET_OFF; | |
46 | else if (k >= SKF_LL_OFF) | |
47 | ptr = skb->mac.raw + k - SKF_LL_OFF; | |
48 | ||
49 | if (ptr >= skb->head && ptr < skb->tail) | |
50 | return ptr; | |
51 | return NULL; | |
52 | } | |
53 | ||
0b05b2a4 | 54 | static inline void *load_pointer(struct sk_buff *skb, int k, |
4ec93edb | 55 | unsigned int size, void *buffer) |
0b05b2a4 PM |
56 | { |
57 | if (k >= 0) | |
58 | return skb_header_pointer(skb, k, size, buffer); | |
59 | else { | |
60 | if (k >= SKF_AD_OFF) | |
61 | return NULL; | |
62 | return __load_pointer(skb, k); | |
63 | } | |
64 | } | |
65 | ||
1da177e4 | 66 | /** |
2966b66c | 67 | * sk_run_filter - run a filter on a socket |
1da177e4 LT |
68 | * @skb: buffer to run the filter on |
69 | * @filter: filter to apply | |
70 | * @flen: length of filter | |
71 | * | |
72 | * Decode and apply filter instructions to the skb->data. | |
73 | * Return length to keep, 0 for none. skb is the data we are | |
74 | * filtering, filter is the array of filter instructions, and | |
75 | * len is the number of filter blocks in the array. | |
76 | */ | |
4bad4dc9 | 77 | unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen) |
1da177e4 | 78 | { |
1da177e4 | 79 | struct sock_filter *fentry; /* We walk down these */ |
0b05b2a4 | 80 | void *ptr; |
2966b66c KK |
81 | u32 A = 0; /* Accumulator */ |
82 | u32 X = 0; /* Index Register */ | |
1da177e4 | 83 | u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */ |
0b05b2a4 | 84 | u32 tmp; |
1da177e4 LT |
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]; | |
4ec93edb | 93 | |
1da177e4 LT |
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: | |
1da177e4 LT |
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; | |
e35bedf3 | 177 | load_w: |
0b05b2a4 PM |
178 | ptr = load_pointer(skb, k, 4, &tmp); |
179 | if (ptr != NULL) { | |
252e3346 | 180 | A = ntohl(get_unaligned((__be32 *)ptr)); |
0b05b2a4 | 181 | continue; |
1da177e4 | 182 | } |
1198ad00 | 183 | break; |
1da177e4 LT |
184 | case BPF_LD|BPF_H|BPF_ABS: |
185 | k = fentry->k; | |
e35bedf3 | 186 | load_h: |
0b05b2a4 PM |
187 | ptr = load_pointer(skb, k, 2, &tmp); |
188 | if (ptr != NULL) { | |
252e3346 | 189 | A = ntohs(get_unaligned((__be16 *)ptr)); |
0b05b2a4 | 190 | continue; |
1da177e4 | 191 | } |
1198ad00 | 192 | break; |
1da177e4 LT |
193 | case BPF_LD|BPF_B|BPF_ABS: |
194 | k = fentry->k; | |
195 | load_b: | |
0b05b2a4 PM |
196 | ptr = load_pointer(skb, k, 1, &tmp); |
197 | if (ptr != NULL) { | |
198 | A = *(u8 *)ptr; | |
199 | continue; | |
1da177e4 | 200 | } |
1198ad00 | 201 | break; |
1da177e4 | 202 | case BPF_LD|BPF_W|BPF_LEN: |
3154e540 | 203 | A = skb->len; |
1da177e4 LT |
204 | continue; |
205 | case BPF_LDX|BPF_W|BPF_LEN: | |
3154e540 | 206 | X = skb->len; |
1da177e4 LT |
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: | |
0b05b2a4 PM |
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; | |
1da177e4 LT |
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: | |
4bad4dc9 | 243 | return fentry->k; |
1da177e4 | 244 | case BPF_RET|BPF_A: |
4bad4dc9 | 245 | return A; |
1da177e4 LT |
246 | case BPF_ST: |
247 | mem[fentry->k] = A; | |
248 | continue; | |
249 | case BPF_STX: | |
250 | mem[fentry->k] = X; | |
251 | continue; | |
252 | default: | |
93699863 | 253 | WARN_ON(1); |
1da177e4 LT |
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: | |
252e3346 | 263 | A = ntohs(skb->protocol); |
1da177e4 LT |
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 | |
93699863 KK |
286 | * no references or jumps that are out of range, no illegal |
287 | * instructions, and must end with a RET instruction. | |
1da177e4 | 288 | * |
7b11f69f KK |
289 | * All jumps are forward as they are not signed. |
290 | * | |
291 | * Returns 0 if the rule set is legal or -EINVAL if not. | |
1da177e4 LT |
292 | */ |
293 | int sk_chk_filter(struct sock_filter *filter, int flen) | |
294 | { | |
295 | struct sock_filter *ftest; | |
296 | int pc; | |
297 | ||
1b93ae64 | 298 | if (flen == 0 || flen > BPF_MAXINSNS) |
1da177e4 LT |
299 | return -EINVAL; |
300 | ||
301 | /* check the filter code now */ | |
302 | for (pc = 0; pc < flen; pc++) { | |
1da177e4 | 303 | ftest = &filter[pc]; |
1da177e4 | 304 | |
93699863 KK |
305 | /* Only allow valid instructions */ |
306 | switch (ftest->code) { | |
307 | case BPF_ALU|BPF_ADD|BPF_K: | |
308 | case BPF_ALU|BPF_ADD|BPF_X: | |
309 | case BPF_ALU|BPF_SUB|BPF_K: | |
310 | case BPF_ALU|BPF_SUB|BPF_X: | |
311 | case BPF_ALU|BPF_MUL|BPF_K: | |
312 | case BPF_ALU|BPF_MUL|BPF_X: | |
313 | case BPF_ALU|BPF_DIV|BPF_X: | |
314 | case BPF_ALU|BPF_AND|BPF_K: | |
315 | case BPF_ALU|BPF_AND|BPF_X: | |
316 | case BPF_ALU|BPF_OR|BPF_K: | |
317 | case BPF_ALU|BPF_OR|BPF_X: | |
318 | case BPF_ALU|BPF_LSH|BPF_K: | |
319 | case BPF_ALU|BPF_LSH|BPF_X: | |
320 | case BPF_ALU|BPF_RSH|BPF_K: | |
321 | case BPF_ALU|BPF_RSH|BPF_X: | |
322 | case BPF_ALU|BPF_NEG: | |
323 | case BPF_LD|BPF_W|BPF_ABS: | |
324 | case BPF_LD|BPF_H|BPF_ABS: | |
325 | case BPF_LD|BPF_B|BPF_ABS: | |
326 | case BPF_LD|BPF_W|BPF_LEN: | |
327 | case BPF_LD|BPF_W|BPF_IND: | |
328 | case BPF_LD|BPF_H|BPF_IND: | |
329 | case BPF_LD|BPF_B|BPF_IND: | |
330 | case BPF_LD|BPF_IMM: | |
331 | case BPF_LDX|BPF_W|BPF_LEN: | |
332 | case BPF_LDX|BPF_B|BPF_MSH: | |
333 | case BPF_LDX|BPF_IMM: | |
334 | case BPF_MISC|BPF_TAX: | |
335 | case BPF_MISC|BPF_TXA: | |
336 | case BPF_RET|BPF_K: | |
337 | case BPF_RET|BPF_A: | |
338 | break; | |
339 | ||
340 | /* Some instructions need special checks */ | |
fb0d366b | 341 | |
93699863 KK |
342 | case BPF_ALU|BPF_DIV|BPF_K: |
343 | /* check for division by zero */ | |
344 | if (ftest->k == 0) | |
1da177e4 | 345 | return -EINVAL; |
93699863 KK |
346 | break; |
347 | ||
348 | case BPF_LD|BPF_MEM: | |
349 | case BPF_LDX|BPF_MEM: | |
350 | case BPF_ST: | |
351 | case BPF_STX: | |
352 | /* check for invalid memory addresses */ | |
353 | if (ftest->k >= BPF_MEMWORDS) | |
354 | return -EINVAL; | |
355 | break; | |
356 | ||
357 | case BPF_JMP|BPF_JA: | |
358 | /* | |
359 | * Note, the large ftest->k might cause loops. | |
360 | * Compare this with conditional jumps below, | |
361 | * where offsets are limited. --ANK (981016) | |
362 | */ | |
363 | if (ftest->k >= (unsigned)(flen-pc-1)) | |
364 | return -EINVAL; | |
365 | break; | |
366 | ||
367 | case BPF_JMP|BPF_JEQ|BPF_K: | |
368 | case BPF_JMP|BPF_JEQ|BPF_X: | |
369 | case BPF_JMP|BPF_JGE|BPF_K: | |
370 | case BPF_JMP|BPF_JGE|BPF_X: | |
371 | case BPF_JMP|BPF_JGT|BPF_K: | |
372 | case BPF_JMP|BPF_JGT|BPF_X: | |
373 | case BPF_JMP|BPF_JSET|BPF_K: | |
374 | case BPF_JMP|BPF_JSET|BPF_X: | |
375 | /* for conditionals both must be safe */ | |
e35bedf3 | 376 | if (pc + ftest->jt + 1 >= flen || |
93699863 KK |
377 | pc + ftest->jf + 1 >= flen) |
378 | return -EINVAL; | |
379 | break; | |
380 | ||
381 | default: | |
382 | return -EINVAL; | |
1da177e4 LT |
383 | } |
384 | } | |
385 | ||
e35bedf3 | 386 | return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL; |
1da177e4 LT |
387 | } |
388 | ||
389 | /** | |
390 | * sk_attach_filter - attach a socket filter | |
391 | * @fprog: the filter program | |
392 | * @sk: the socket to use | |
393 | * | |
394 | * Attach the user's filter code. We first run some sanity checks on | |
395 | * it to make sure it does not explode on us later. If an error | |
396 | * occurs or there is insufficient memory for the filter a negative | |
397 | * errno code is returned. On success the return is zero. | |
398 | */ | |
399 | int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) | |
400 | { | |
4ec93edb | 401 | struct sk_filter *fp; |
1da177e4 LT |
402 | unsigned int fsize = sizeof(struct sock_filter) * fprog->len; |
403 | int err; | |
404 | ||
405 | /* Make sure new filter is there and in the right amounts. */ | |
e35bedf3 KK |
406 | if (fprog->filter == NULL) |
407 | return -EINVAL; | |
1da177e4 LT |
408 | |
409 | fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL); | |
410 | if (!fp) | |
411 | return -ENOMEM; | |
412 | if (copy_from_user(fp->insns, fprog->filter, fsize)) { | |
4ec93edb | 413 | sock_kfree_s(sk, fp, fsize+sizeof(*fp)); |
1da177e4 LT |
414 | return -EFAULT; |
415 | } | |
416 | ||
417 | atomic_set(&fp->refcnt, 1); | |
418 | fp->len = fprog->len; | |
419 | ||
420 | err = sk_chk_filter(fp->insns, fp->len); | |
421 | if (!err) { | |
422 | struct sk_filter *old_fp; | |
423 | ||
fda9ef5d DM |
424 | rcu_read_lock_bh(); |
425 | old_fp = rcu_dereference(sk->sk_filter); | |
426 | rcu_assign_pointer(sk->sk_filter, fp); | |
427 | rcu_read_unlock_bh(); | |
1da177e4 LT |
428 | fp = old_fp; |
429 | } | |
430 | ||
431 | if (fp) | |
432 | sk_filter_release(sk, fp); | |
433 | return err; | |
434 | } | |
435 | ||
436 | EXPORT_SYMBOL(sk_chk_filter); | |
437 | EXPORT_SYMBOL(sk_run_filter); |