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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> | |
21 | #include <linux/sched.h> | |
22 | #include <linux/mm.h> | |
23 | #include <linux/fcntl.h> | |
24 | #include <linux/socket.h> | |
25 | #include <linux/in.h> | |
26 | #include <linux/inet.h> | |
27 | #include <linux/netdevice.h> | |
28 | #include <linux/if_packet.h> | |
29 | #include <net/ip.h> | |
30 | #include <net/protocol.h> | |
31 | #include <linux/skbuff.h> | |
32 | #include <net/sock.h> | |
33 | #include <linux/errno.h> | |
34 | #include <linux/timer.h> | |
35 | #include <asm/system.h> | |
36 | #include <asm/uaccess.h> | |
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 PM |
54 | static inline void *load_pointer(struct sk_buff *skb, int k, |
55 | unsigned int size, void *buffer) | |
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 LT |
66 | /** |
67 | * sk_run_filter - run a filter on a socket | |
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 | */ | |
77 | ||
78 | int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen) | |
79 | { | |
1da177e4 | 80 | struct sock_filter *fentry; /* We walk down these */ |
0b05b2a4 | 81 | void *ptr; |
1da177e4 LT |
82 | u32 A = 0; /* Accumulator */ |
83 | u32 X = 0; /* Index Register */ | |
84 | u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */ | |
0b05b2a4 | 85 | u32 tmp; |
1da177e4 LT |
86 | int k; |
87 | int pc; | |
88 | ||
89 | /* | |
90 | * Process array of filter instructions. | |
91 | */ | |
92 | for (pc = 0; pc < flen; pc++) { | |
93 | fentry = &filter[pc]; | |
94 | ||
95 | switch (fentry->code) { | |
96 | case BPF_ALU|BPF_ADD|BPF_X: | |
97 | A += X; | |
98 | continue; | |
99 | case BPF_ALU|BPF_ADD|BPF_K: | |
100 | A += fentry->k; | |
101 | continue; | |
102 | case BPF_ALU|BPF_SUB|BPF_X: | |
103 | A -= X; | |
104 | continue; | |
105 | case BPF_ALU|BPF_SUB|BPF_K: | |
106 | A -= fentry->k; | |
107 | continue; | |
108 | case BPF_ALU|BPF_MUL|BPF_X: | |
109 | A *= X; | |
110 | continue; | |
111 | case BPF_ALU|BPF_MUL|BPF_K: | |
112 | A *= fentry->k; | |
113 | continue; | |
114 | case BPF_ALU|BPF_DIV|BPF_X: | |
115 | if (X == 0) | |
116 | return 0; | |
117 | A /= X; | |
118 | continue; | |
119 | case BPF_ALU|BPF_DIV|BPF_K: | |
1da177e4 LT |
120 | A /= fentry->k; |
121 | continue; | |
122 | case BPF_ALU|BPF_AND|BPF_X: | |
123 | A &= X; | |
124 | continue; | |
125 | case BPF_ALU|BPF_AND|BPF_K: | |
126 | A &= fentry->k; | |
127 | continue; | |
128 | case BPF_ALU|BPF_OR|BPF_X: | |
129 | A |= X; | |
130 | continue; | |
131 | case BPF_ALU|BPF_OR|BPF_K: | |
132 | A |= fentry->k; | |
133 | continue; | |
134 | case BPF_ALU|BPF_LSH|BPF_X: | |
135 | A <<= X; | |
136 | continue; | |
137 | case BPF_ALU|BPF_LSH|BPF_K: | |
138 | A <<= fentry->k; | |
139 | continue; | |
140 | case BPF_ALU|BPF_RSH|BPF_X: | |
141 | A >>= X; | |
142 | continue; | |
143 | case BPF_ALU|BPF_RSH|BPF_K: | |
144 | A >>= fentry->k; | |
145 | continue; | |
146 | case BPF_ALU|BPF_NEG: | |
147 | A = -A; | |
148 | continue; | |
149 | case BPF_JMP|BPF_JA: | |
150 | pc += fentry->k; | |
151 | continue; | |
152 | case BPF_JMP|BPF_JGT|BPF_K: | |
153 | pc += (A > fentry->k) ? fentry->jt : fentry->jf; | |
154 | continue; | |
155 | case BPF_JMP|BPF_JGE|BPF_K: | |
156 | pc += (A >= fentry->k) ? fentry->jt : fentry->jf; | |
157 | continue; | |
158 | case BPF_JMP|BPF_JEQ|BPF_K: | |
159 | pc += (A == fentry->k) ? fentry->jt : fentry->jf; | |
160 | continue; | |
161 | case BPF_JMP|BPF_JSET|BPF_K: | |
162 | pc += (A & fentry->k) ? fentry->jt : fentry->jf; | |
163 | continue; | |
164 | case BPF_JMP|BPF_JGT|BPF_X: | |
165 | pc += (A > X) ? fentry->jt : fentry->jf; | |
166 | continue; | |
167 | case BPF_JMP|BPF_JGE|BPF_X: | |
168 | pc += (A >= X) ? fentry->jt : fentry->jf; | |
169 | continue; | |
170 | case BPF_JMP|BPF_JEQ|BPF_X: | |
171 | pc += (A == X) ? fentry->jt : fentry->jf; | |
172 | continue; | |
173 | case BPF_JMP|BPF_JSET|BPF_X: | |
174 | pc += (A & X) ? fentry->jt : fentry->jf; | |
175 | continue; | |
176 | case BPF_LD|BPF_W|BPF_ABS: | |
177 | k = fentry->k; | |
178 | load_w: | |
0b05b2a4 PM |
179 | ptr = load_pointer(skb, k, 4, &tmp); |
180 | if (ptr != NULL) { | |
181 | A = ntohl(*(u32 *)ptr); | |
182 | continue; | |
1da177e4 | 183 | } |
1198ad00 | 184 | break; |
1da177e4 LT |
185 | case BPF_LD|BPF_H|BPF_ABS: |
186 | k = fentry->k; | |
187 | load_h: | |
0b05b2a4 PM |
188 | ptr = load_pointer(skb, k, 2, &tmp); |
189 | if (ptr != NULL) { | |
190 | A = ntohs(*(u16 *)ptr); | |
191 | continue; | |
1da177e4 | 192 | } |
1198ad00 | 193 | break; |
1da177e4 LT |
194 | case BPF_LD|BPF_B|BPF_ABS: |
195 | k = fentry->k; | |
196 | load_b: | |
0b05b2a4 PM |
197 | ptr = load_pointer(skb, k, 1, &tmp); |
198 | if (ptr != NULL) { | |
199 | A = *(u8 *)ptr; | |
200 | continue; | |
1da177e4 | 201 | } |
1198ad00 | 202 | break; |
1da177e4 | 203 | case BPF_LD|BPF_W|BPF_LEN: |
3154e540 | 204 | A = skb->len; |
1da177e4 LT |
205 | continue; |
206 | case BPF_LDX|BPF_W|BPF_LEN: | |
3154e540 | 207 | X = skb->len; |
1da177e4 LT |
208 | continue; |
209 | case BPF_LD|BPF_W|BPF_IND: | |
210 | k = X + fentry->k; | |
211 | goto load_w; | |
212 | case BPF_LD|BPF_H|BPF_IND: | |
213 | k = X + fentry->k; | |
214 | goto load_h; | |
215 | case BPF_LD|BPF_B|BPF_IND: | |
216 | k = X + fentry->k; | |
217 | goto load_b; | |
218 | case BPF_LDX|BPF_B|BPF_MSH: | |
0b05b2a4 PM |
219 | ptr = load_pointer(skb, fentry->k, 1, &tmp); |
220 | if (ptr != NULL) { | |
221 | X = (*(u8 *)ptr & 0xf) << 2; | |
222 | continue; | |
223 | } | |
224 | return 0; | |
1da177e4 LT |
225 | case BPF_LD|BPF_IMM: |
226 | A = fentry->k; | |
227 | continue; | |
228 | case BPF_LDX|BPF_IMM: | |
229 | X = fentry->k; | |
230 | continue; | |
231 | case BPF_LD|BPF_MEM: | |
232 | A = mem[fentry->k]; | |
233 | continue; | |
234 | case BPF_LDX|BPF_MEM: | |
235 | X = mem[fentry->k]; | |
236 | continue; | |
237 | case BPF_MISC|BPF_TAX: | |
238 | X = A; | |
239 | continue; | |
240 | case BPF_MISC|BPF_TXA: | |
241 | A = X; | |
242 | continue; | |
243 | case BPF_RET|BPF_K: | |
244 | return ((unsigned int)fentry->k); | |
245 | case BPF_RET|BPF_A: | |
246 | return ((unsigned int)A); | |
247 | case BPF_ST: | |
248 | mem[fentry->k] = A; | |
249 | continue; | |
250 | case BPF_STX: | |
251 | mem[fentry->k] = X; | |
252 | continue; | |
253 | default: | |
93699863 | 254 | WARN_ON(1); |
1da177e4 LT |
255 | return 0; |
256 | } | |
257 | ||
258 | /* | |
259 | * Handle ancillary data, which are impossible | |
260 | * (or very difficult) to get parsing packet contents. | |
261 | */ | |
262 | switch (k-SKF_AD_OFF) { | |
263 | case SKF_AD_PROTOCOL: | |
264 | A = htons(skb->protocol); | |
265 | continue; | |
266 | case SKF_AD_PKTTYPE: | |
267 | A = skb->pkt_type; | |
268 | continue; | |
269 | case SKF_AD_IFINDEX: | |
270 | A = skb->dev->ifindex; | |
271 | continue; | |
272 | default: | |
273 | return 0; | |
274 | } | |
275 | } | |
276 | ||
277 | return 0; | |
278 | } | |
279 | ||
280 | /** | |
281 | * sk_chk_filter - verify socket filter code | |
282 | * @filter: filter to verify | |
283 | * @flen: length of filter | |
284 | * | |
285 | * Check the user's filter code. If we let some ugly | |
286 | * filter code slip through kaboom! The filter must contain | |
93699863 KK |
287 | * no references or jumps that are out of range, no illegal |
288 | * instructions, and must end with a RET instruction. | |
1da177e4 LT |
289 | * |
290 | * Returns 0 if the rule set is legal or a negative errno code if not. | |
291 | */ | |
292 | int sk_chk_filter(struct sock_filter *filter, int flen) | |
293 | { | |
294 | struct sock_filter *ftest; | |
295 | int pc; | |
296 | ||
1b93ae64 | 297 | if (flen == 0 || flen > BPF_MAXINSNS) |
1da177e4 LT |
298 | return -EINVAL; |
299 | ||
300 | /* check the filter code now */ | |
301 | for (pc = 0; pc < flen; pc++) { | |
302 | /* all jumps are forward as they are not signed */ | |
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 */ | |
376 | if (pc + ftest->jt + 1 >= flen || | |
377 | pc + ftest->jf + 1 >= flen) | |
378 | return -EINVAL; | |
379 | break; | |
380 | ||
381 | default: | |
382 | return -EINVAL; | |
1da177e4 LT |
383 | } |
384 | } | |
385 | ||
386 | /* | |
387 | * The program must end with a return. We don't care where they | |
388 | * jumped within the script (its always forwards) but in the end | |
389 | * they _will_ hit this. | |
390 | */ | |
391 | return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL; | |
392 | } | |
393 | ||
394 | /** | |
395 | * sk_attach_filter - attach a socket filter | |
396 | * @fprog: the filter program | |
397 | * @sk: the socket to use | |
398 | * | |
399 | * Attach the user's filter code. We first run some sanity checks on | |
400 | * it to make sure it does not explode on us later. If an error | |
401 | * occurs or there is insufficient memory for the filter a negative | |
402 | * errno code is returned. On success the return is zero. | |
403 | */ | |
404 | int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) | |
405 | { | |
406 | struct sk_filter *fp; | |
407 | unsigned int fsize = sizeof(struct sock_filter) * fprog->len; | |
408 | int err; | |
409 | ||
410 | /* Make sure new filter is there and in the right amounts. */ | |
1b93ae64 | 411 | if (fprog->filter == NULL) |
1da177e4 LT |
412 | return -EINVAL; |
413 | ||
414 | fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL); | |
415 | if (!fp) | |
416 | return -ENOMEM; | |
417 | if (copy_from_user(fp->insns, fprog->filter, fsize)) { | |
418 | sock_kfree_s(sk, fp, fsize+sizeof(*fp)); | |
419 | return -EFAULT; | |
420 | } | |
421 | ||
422 | atomic_set(&fp->refcnt, 1); | |
423 | fp->len = fprog->len; | |
424 | ||
425 | err = sk_chk_filter(fp->insns, fp->len); | |
426 | if (!err) { | |
427 | struct sk_filter *old_fp; | |
428 | ||
429 | spin_lock_bh(&sk->sk_lock.slock); | |
430 | old_fp = sk->sk_filter; | |
431 | sk->sk_filter = fp; | |
432 | spin_unlock_bh(&sk->sk_lock.slock); | |
433 | fp = old_fp; | |
434 | } | |
435 | ||
436 | if (fp) | |
437 | sk_filter_release(sk, fp); | |
438 | return err; | |
439 | } | |
440 | ||
441 | EXPORT_SYMBOL(sk_chk_filter); | |
442 | EXPORT_SYMBOL(sk_run_filter); |