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