?  search:
summary | log | graphiclog1 | graphiclog2 | commit | commitdiff | tree | refs | edit | fork
blame | history | raw | HEAD
staging: rtl8192e: Fix UNNECESSARY_ELSE warning
[linux-2.6/btrfs-unstable.git] / net / core / filter.c
blobf6bdc2b1ba01295a53be71b4043437a82848d1c6
1 /*
2 * Linux Socket Filter - Kernel level socket filtering
3 *
4 * Based on the design of the Berkeley Packet Filter. The new
5 * internal format has been designed by PLUMgrid:
6 *
7 * Copyright (c) 2011 - 2014 PLUMgrid, http://plumgrid.com
8 *
9 * Authors:
10 *
11 * Jay Schulist <jschlst@samba.org>
12 * Alexei Starovoitov <ast@plumgrid.com>
13 * Daniel Borkmann <dborkman@redhat.com>
14 *
15 * This program is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public License
17 * as published by the Free Software Foundation; either version
18 * 2 of the License, or (at your option) any later version.
19 *
20 * Andi Kleen - Fix a few bad bugs and races.
21 * Kris Katterjohn - Added many additional checks in bpf_check_classic()
22 */
23
24 #include <linux/module.h>
25 #include <linux/types.h>
26 #include <linux/mm.h>
27 #include <linux/fcntl.h>
28 #include <linux/socket.h>
29 #include <linux/in.h>
30 #include <linux/inet.h>
31 #include <linux/netdevice.h>
32 #include <linux/if_packet.h>
33 #include <linux/gfp.h>
34 #include <net/ip.h>
35 #include <net/protocol.h>
36 #include <net/netlink.h>
37 #include <linux/skbuff.h>
38 #include <net/sock.h>
39 #include <linux/errno.h>
40 #include <linux/timer.h>
41 #include <asm/uaccess.h>
42 #include <asm/unaligned.h>
43 #include <linux/filter.h>
44 #include <linux/ratelimit.h>
45 #include <linux/seccomp.h>
46 #include <linux/if_vlan.h>
47 #include <linux/bpf.h>
48
49 /**
50 * sk_filter - run a packet through a socket filter
51 * @sk: sock associated with &sk_buff
52 * @skb: buffer to filter
53 *
54 * Run the filter code and then cut skb->data to correct size returned by
55 * SK_RUN_FILTER. If pkt_len is 0 we toss packet. If skb->len is smaller
56 * than pkt_len we keep whole skb->data. This is the socket level
57 * wrapper to SK_RUN_FILTER. It returns 0 if the packet should
58 * be accepted or -EPERM if the packet should be tossed.
59 *
60 */
61 int sk_filter(struct sock *sk, struct sk_buff *skb)
62 {
63 int err;
64 struct sk_filter *filter;
65
66 /*
67 * If the skb was allocated from pfmemalloc reserves, only
68 * allow SOCK_MEMALLOC sockets to use it as this socket is
69 * helping free memory
70 */
71 if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
72 return -ENOMEM;
73
74 err = security_sock_rcv_skb(sk, skb);
75 if (err)
76 return err;
77
78 rcu_read_lock();
79 filter = rcu_dereference(sk->sk_filter);
80 if (filter) {
81 unsigned int pkt_len = SK_RUN_FILTER(filter, skb);
82
83 err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
84 }
85 rcu_read_unlock();
86
87 return err;
88 }
89 EXPORT_SYMBOL(sk_filter);
90
91 static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
92 {
93 return skb_get_poff((struct sk_buff *)(unsigned long) ctx);
94 }
95
96 static u64 __skb_get_nlattr(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
97 {
98 struct sk_buff *skb = (struct sk_buff *)(unsigned long) ctx;
99 struct nlattr *nla;
100
101 if (skb_is_nonlinear(skb))
102 return 0;
103
104 if (skb->len < sizeof(struct nlattr))
105 return 0;
106
107 if (a > skb->len - sizeof(struct nlattr))
108 return 0;
109
110 nla = nla_find((struct nlattr *) &skb->data[a], skb->len - a, x);
111 if (nla)
112 return (void *) nla - (void *) skb->data;
113
114 return 0;
115 }
116
117 static u64 __skb_get_nlattr_nest(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
118 {
119 struct sk_buff *skb = (struct sk_buff *)(unsigned long) ctx;
120 struct nlattr *nla;
121
122 if (skb_is_nonlinear(skb))
123 return 0;
124
125 if (skb->len < sizeof(struct nlattr))
126 return 0;
127
128 if (a > skb->len - sizeof(struct nlattr))
129 return 0;
130
131 nla = (struct nlattr *) &skb->data[a];
132 if (nla->nla_len > skb->len - a)
133 return 0;
134
135 nla = nla_find_nested(nla, x);
136 if (nla)
137 return (void *) nla - (void *) skb->data;
138
139 return 0;
140 }
141
142 static u64 __get_raw_cpu_id(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
143 {
144 return raw_smp_processor_id();
145 }
146
147 /* note that this only generates 32-bit random numbers */
148 static u64 __get_random_u32(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
149 {
150 return prandom_u32();
151 }
152
153 static bool convert_bpf_extensions(struct sock_filter *fp,
154 struct bpf_insn **insnp)
155 {
156 struct bpf_insn *insn = *insnp;
157
158 switch (fp->k) {
159 case SKF_AD_OFF + SKF_AD_PROTOCOL:
160 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
161
162 /* A = *(u16 *) (CTX + offsetof(protocol)) */
163 *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
164 offsetof(struct sk_buff, protocol));
165 /* A = ntohs(A) [emitting a nop or swap16] */
166 *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
167 break;
168
169 case SKF_AD_OFF + SKF_AD_PKTTYPE:
170 *insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_A, BPF_REG_CTX,
171 PKT_TYPE_OFFSET());
172 *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, PKT_TYPE_MAX);
173 #ifdef __BIG_ENDIAN_BITFIELD
174 insn++;
175 *insn = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 5);
176 #endif
177 break;
178
179 case SKF_AD_OFF + SKF_AD_IFINDEX:
180 case SKF_AD_OFF + SKF_AD_HATYPE:
181 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
182 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);
183 BUILD_BUG_ON(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)) < 0);
184
185 *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
186 BPF_REG_TMP, BPF_REG_CTX,
187 offsetof(struct sk_buff, dev));
188 /* if (tmp != 0) goto pc + 1 */
189 *insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_TMP, 0, 1);
190 *insn++ = BPF_EXIT_INSN();
191 if (fp->k == SKF_AD_OFF + SKF_AD_IFINDEX)
192 *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_TMP,
193 offsetof(struct net_device, ifindex));
194 else
195 *insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_TMP,
196 offsetof(struct net_device, type));
197 break;
198
199 case SKF_AD_OFF + SKF_AD_MARK:
200 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
201
202 *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
203 offsetof(struct sk_buff, mark));
204 break;
205
206 case SKF_AD_OFF + SKF_AD_RXHASH:
207 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
208
209 *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
210 offsetof(struct sk_buff, hash));
211 break;
212
213 case SKF_AD_OFF + SKF_AD_QUEUE:
214 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);
215
216 *insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
217 offsetof(struct sk_buff, queue_mapping));
218 break;
219
220 case SKF_AD_OFF + SKF_AD_VLAN_TAG:
221 case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
222 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
223 BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
224
225 /* A = *(u16 *) (CTX + offsetof(vlan_tci)) */
226 *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
227 offsetof(struct sk_buff, vlan_tci));
228 if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {
229 *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,
230 ~VLAN_TAG_PRESENT);
231 } else {
232 /* A >>= 12 */
233 *insn++ = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);
234 /* A &= 1 */
235 *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);
236 }
237 break;
238
239 case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
240 case SKF_AD_OFF + SKF_AD_NLATTR:
241 case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
242 case SKF_AD_OFF + SKF_AD_CPU:
243 case SKF_AD_OFF + SKF_AD_RANDOM:
244 /* arg1 = CTX */
245 *insn++ = BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX);
246 /* arg2 = A */
247 *insn++ = BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_A);
248 /* arg3 = X */
249 *insn++ = BPF_MOV64_REG(BPF_REG_ARG3, BPF_REG_X);
250 /* Emit call(arg1=CTX, arg2=A, arg3=X) */
251 switch (fp->k) {
252 case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
253 *insn = BPF_EMIT_CALL(__skb_get_pay_offset);
254 break;
255 case SKF_AD_OFF + SKF_AD_NLATTR:
256 *insn = BPF_EMIT_CALL(__skb_get_nlattr);
257 break;
258 case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
259 *insn = BPF_EMIT_CALL(__skb_get_nlattr_nest);
260 break;
261 case SKF_AD_OFF + SKF_AD_CPU:
262 *insn = BPF_EMIT_CALL(__get_raw_cpu_id);
263 break;
264 case SKF_AD_OFF + SKF_AD_RANDOM:
265 *insn = BPF_EMIT_CALL(__get_random_u32);
266 break;
267 }
268 break;
269
270 case SKF_AD_OFF + SKF_AD_ALU_XOR_X:
271 /* A ^= X */
272 *insn = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_X);
273 break;
274
275 default:
276 /* This is just a dummy call to avoid letting the compiler
277 * evict __bpf_call_base() as an optimization. Placed here
278 * where no-one bothers.
279 */
280 BUG_ON(__bpf_call_base(0, 0, 0, 0, 0) != 0);
281 return false;
282 }
283
284 *insnp = insn;
285 return true;
286 }
287
288 /**
289 * bpf_convert_filter - convert filter program
290 * @prog: the user passed filter program
291 * @len: the length of the user passed filter program
292 * @new_prog: buffer where converted program will be stored
293 * @new_len: pointer to store length of converted program
294 *
295 * Remap 'sock_filter' style BPF instruction set to 'sock_filter_ext' style.
296 * Conversion workflow:
297 *
298 * 1) First pass for calculating the new program length:
299 * bpf_convert_filter(old_prog, old_len, NULL, &new_len)
300 *
301 * 2) 2nd pass to remap in two passes: 1st pass finds new
302 * jump offsets, 2nd pass remapping:
303 * new_prog = kmalloc(sizeof(struct bpf_insn) * new_len);
304 * bpf_convert_filter(old_prog, old_len, new_prog, &new_len);
305 *
306 * User BPF's register A is mapped to our BPF register 6, user BPF
307 * register X is mapped to BPF register 7; frame pointer is always
308 * register 10; Context 'void *ctx' is stored in register 1, that is,
309 * for socket filters: ctx == 'struct sk_buff *', for seccomp:
310 * ctx == 'struct seccomp_data *'.
311 */
312 int bpf_convert_filter(struct sock_filter *prog, int len,
313 struct bpf_insn *new_prog, int *new_len)
314 {
315 int new_flen = 0, pass = 0, target, i;
316 struct bpf_insn *new_insn;
317 struct sock_filter *fp;
318 int *addrs = NULL;
319 u8 bpf_src;
320
321 BUILD_BUG_ON(BPF_MEMWORDS * sizeof(u32) > MAX_BPF_STACK);
322 BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
323
324 if (len <= 0 || len > BPF_MAXINSNS)
325 return -EINVAL;
326
327 if (new_prog) {
328 addrs = kcalloc(len, sizeof(*addrs), GFP_KERNEL);
329 if (!addrs)
330 return -ENOMEM;
331 }
332
333 do_pass:
334 new_insn = new_prog;
335 fp = prog;
336
337 if (new_insn)
338 *new_insn = BPF_MOV64_REG(BPF_REG_CTX, BPF_REG_ARG1);
339 new_insn++;
340
341 for (i = 0; i < len; fp++, i++) {
342 struct bpf_insn tmp_insns[6] = { };
343 struct bpf_insn *insn = tmp_insns;
344
345 if (addrs)
346 addrs[i] = new_insn - new_prog;
347
348 switch (fp->code) {
349 /* All arithmetic insns and skb loads map as-is. */
350 case BPF_ALU | BPF_ADD | BPF_X:
351 case BPF_ALU | BPF_ADD | BPF_K:
352 case BPF_ALU | BPF_SUB | BPF_X:
353 case BPF_ALU | BPF_SUB | BPF_K:
354 case BPF_ALU | BPF_AND | BPF_X:
355 case BPF_ALU | BPF_AND | BPF_K:
356 case BPF_ALU | BPF_OR | BPF_X:
357 case BPF_ALU | BPF_OR | BPF_K:
358 case BPF_ALU | BPF_LSH | BPF_X:
359 case BPF_ALU | BPF_LSH | BPF_K:
360 case BPF_ALU | BPF_RSH | BPF_X:
361 case BPF_ALU | BPF_RSH | BPF_K:
362 case BPF_ALU | BPF_XOR | BPF_X:
363 case BPF_ALU | BPF_XOR | BPF_K:
364 case BPF_ALU | BPF_MUL | BPF_X:
365 case BPF_ALU | BPF_MUL | BPF_K:
366 case BPF_ALU | BPF_DIV | BPF_X:
367 case BPF_ALU | BPF_DIV | BPF_K:
368 case BPF_ALU | BPF_MOD | BPF_X:
369 case BPF_ALU | BPF_MOD | BPF_K:
370 case BPF_ALU | BPF_NEG:
371 case BPF_LD | BPF_ABS | BPF_W:
372 case BPF_LD | BPF_ABS | BPF_H:
373 case BPF_LD | BPF_ABS | BPF_B:
374 case BPF_LD | BPF_IND | BPF_W:
375 case BPF_LD | BPF_IND | BPF_H:
376 case BPF_LD | BPF_IND | BPF_B:
377 /* Check for overloaded BPF extension and
378 * directly convert it if found, otherwise
379 * just move on with mapping.
380 */
381 if (BPF_CLASS(fp->code) == BPF_LD &&
382 BPF_MODE(fp->code) == BPF_ABS &&
383 convert_bpf_extensions(fp, &insn))
384 break;
385
386 *insn = BPF_RAW_INSN(fp->code, BPF_REG_A, BPF_REG_X, 0, fp->k);
387 break;
388
389 /* Jump transformation cannot use BPF block macros
390 * everywhere as offset calculation and target updates
391 * require a bit more work than the rest, i.e. jump
392 * opcodes map as-is, but offsets need adjustment.
393 */
394
395 #define BPF_EMIT_JMP \
396 do { \
397 if (target >= len || target < 0) \
398 goto err; \
399 insn->off = addrs ? addrs[target] - addrs[i] - 1 : 0; \
400 /* Adjust pc relative offset for 2nd or 3rd insn. */ \
401 insn->off -= insn - tmp_insns; \
402 } while (0)
403
404 case BPF_JMP | BPF_JA:
405 target = i + fp->k + 1;
406 insn->code = fp->code;
407 BPF_EMIT_JMP;
408 break;
409
410 case BPF_JMP | BPF_JEQ | BPF_K:
411 case BPF_JMP | BPF_JEQ | BPF_X:
412 case BPF_JMP | BPF_JSET | BPF_K:
413 case BPF_JMP | BPF_JSET | BPF_X:
414 case BPF_JMP | BPF_JGT | BPF_K:
415 case BPF_JMP | BPF_JGT | BPF_X:
416 case BPF_JMP | BPF_JGE | BPF_K:
417 case BPF_JMP | BPF_JGE | BPF_X:
418 if (BPF_SRC(fp->code) == BPF_K && (int) fp->k < 0) {
419 /* BPF immediates are signed, zero extend
420 * immediate into tmp register and use it
421 * in compare insn.
422 */
423 *insn++ = BPF_MOV32_IMM(BPF_REG_TMP, fp->k);
424
425 insn->dst_reg = BPF_REG_A;
426 insn->src_reg = BPF_REG_TMP;
427 bpf_src = BPF_X;
428 } else {
429 insn->dst_reg = BPF_REG_A;
430 insn->src_reg = BPF_REG_X;
431 insn->imm = fp->k;
432 bpf_src = BPF_SRC(fp->code);
433 }
434
435 /* Common case where 'jump_false' is next insn. */
436 if (fp->jf == 0) {
437 insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
438 target = i + fp->jt + 1;
439 BPF_EMIT_JMP;
440 break;
441 }
442
443 /* Convert JEQ into JNE when 'jump_true' is next insn. */
444 if (fp->jt == 0 && BPF_OP(fp->code) == BPF_JEQ) {
445 insn->code = BPF_JMP | BPF_JNE | bpf_src;
446 target = i + fp->jf + 1;
447 BPF_EMIT_JMP;
448 break;
449 }
450
451 /* Other jumps are mapped into two insns: Jxx and JA. */
452 target = i + fp->jt + 1;
453 insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
454 BPF_EMIT_JMP;
455 insn++;
456
457 insn->code = BPF_JMP | BPF_JA;
458 target = i + fp->jf + 1;
459 BPF_EMIT_JMP;
460 break;
461
462 /* ldxb 4 * ([14] & 0xf) is remaped into 6 insns. */
463 case BPF_LDX | BPF_MSH | BPF_B:
464 /* tmp = A */
465 *insn++ = BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_A);
466 /* A = BPF_R0 = *(u8 *) (skb->data + K) */
467 *insn++ = BPF_LD_ABS(BPF_B, fp->k);
468 /* A &= 0xf */
469 *insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 0xf);
470 /* A <<= 2 */
471 *insn++ = BPF_ALU32_IMM(BPF_LSH, BPF_REG_A, 2);
472 /* X = A */
473 *insn++ = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
474 /* A = tmp */
475 *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_TMP);
476 break;
477
478 /* RET_K, RET_A are remaped into 2 insns. */
479 case BPF_RET | BPF_A:
480 case BPF_RET | BPF_K:
481 *insn++ = BPF_MOV32_RAW(BPF_RVAL(fp->code) == BPF_K ?
482 BPF_K : BPF_X, BPF_REG_0,
483 BPF_REG_A, fp->k);
484 *insn = BPF_EXIT_INSN();
485 break;
486
487 /* Store to stack. */
488 case BPF_ST:
489 case BPF_STX:
490 *insn = BPF_STX_MEM(BPF_W, BPF_REG_FP, BPF_CLASS(fp->code) ==
491 BPF_ST ? BPF_REG_A : BPF_REG_X,
492 -(BPF_MEMWORDS - fp->k) * 4);
493 break;
494
495 /* Load from stack. */
496 case BPF_LD | BPF_MEM:
497 case BPF_LDX | BPF_MEM:
498 *insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD ?
499 BPF_REG_A : BPF_REG_X, BPF_REG_FP,
500 -(BPF_MEMWORDS - fp->k) * 4);
501 break;
502
503 /* A = K or X = K */
504 case BPF_LD | BPF_IMM:
505 case BPF_LDX | BPF_IMM:
506 *insn = BPF_MOV32_IMM(BPF_CLASS(fp->code) == BPF_LD ?
507 BPF_REG_A : BPF_REG_X, fp->k);
508 break;
509
510 /* X = A */
511 case BPF_MISC | BPF_TAX:
512 *insn = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
513 break;
514
515 /* A = X */
516 case BPF_MISC | BPF_TXA:
517 *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_X);
518 break;
519
520 /* A = skb->len or X = skb->len */
521 case BPF_LD | BPF_W | BPF_LEN:
522 case BPF_LDX | BPF_W | BPF_LEN:
523 *insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD ?
524 BPF_REG_A : BPF_REG_X, BPF_REG_CTX,
525 offsetof(struct sk_buff, len));
526 break;
527
528 /* Access seccomp_data fields. */
529 case BPF_LDX | BPF_ABS | BPF_W:
530 /* A = *(u32 *) (ctx + K) */
531 *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX, fp->k);
532 break;
533
534 /* Unknown instruction. */
535 default:
536 goto err;
537 }
538
539 insn++;
540 if (new_prog)
541 memcpy(new_insn, tmp_insns,
542 sizeof(*insn) * (insn - tmp_insns));
543 new_insn += insn - tmp_insns;
544 }
545
546 if (!new_prog) {
547 /* Only calculating new length. */
548 *new_len = new_insn - new_prog;
549 return 0;
550 }
551
552 pass++;
553 if (new_flen != new_insn - new_prog) {
554 new_flen = new_insn - new_prog;
555 if (pass > 2)
556 goto err;
557 goto do_pass;
558 }
559
560 kfree(addrs);
561 BUG_ON(*new_len != new_flen);
562 return 0;
563 err:
564 kfree(addrs);
565 return -EINVAL;
566 }
567
568 /* Security:
569 *
570 * As we dont want to clear mem[] array for each packet going through
571 * __bpf_prog_run(), we check that filter loaded by user never try to read
572 * a cell if not previously written, and we check all branches to be sure
573 * a malicious user doesn't try to abuse us.
574 */
575 static int check_load_and_stores(const struct sock_filter *filter, int flen)
576 {
577 u16 *masks, memvalid = 0; /* One bit per cell, 16 cells */
578 int pc, ret = 0;
579
580 BUILD_BUG_ON(BPF_MEMWORDS > 16);
581
582 masks = kmalloc_array(flen, sizeof(*masks), GFP_KERNEL);
583 if (!masks)
584 return -ENOMEM;
585
586 memset(masks, 0xff, flen * sizeof(*masks));
587
588 for (pc = 0; pc < flen; pc++) {
589 memvalid &= masks[pc];
590
591 switch (filter[pc].code) {
592 case BPF_ST:
593 case BPF_STX:
594 memvalid |= (1 << filter[pc].k);
595 break;
596 case BPF_LD | BPF_MEM:
597 case BPF_LDX | BPF_MEM:
598 if (!(memvalid & (1 << filter[pc].k))) {
599 ret = -EINVAL;
600 goto error;
601 }
602 break;
603 case BPF_JMP | BPF_JA:
604 /* A jump must set masks on target */
605 masks[pc + 1 + filter[pc].k] &= memvalid;
606 memvalid = ~0;
607 break;
608 case BPF_JMP | BPF_JEQ | BPF_K:
609 case BPF_JMP | BPF_JEQ | BPF_X:
610 case BPF_JMP | BPF_JGE | BPF_K:
611 case BPF_JMP | BPF_JGE | BPF_X:
612 case BPF_JMP | BPF_JGT | BPF_K:
613 case BPF_JMP | BPF_JGT | BPF_X:
614 case BPF_JMP | BPF_JSET | BPF_K:
615 case BPF_JMP | BPF_JSET | BPF_X:
616 /* A jump must set masks on targets */
617 masks[pc + 1 + filter[pc].jt] &= memvalid;
618 masks[pc + 1 + filter[pc].jf] &= memvalid;
619 memvalid = ~0;
620 break;
621 }
622 }
623 error:
624 kfree(masks);
625 return ret;
626 }
627
628 static bool chk_code_allowed(u16 code_to_probe)
629 {
630 static const bool codes[] = {
631 /* 32 bit ALU operations */
632 [BPF_ALU | BPF_ADD | BPF_K] = true,
633 [BPF_ALU | BPF_ADD | BPF_X] = true,
634 [BPF_ALU | BPF_SUB | BPF_K] = true,
635 [BPF_ALU | BPF_SUB | BPF_X] = true,
636 [BPF_ALU | BPF_MUL | BPF_K] = true,
637 [BPF_ALU | BPF_MUL | BPF_X] = true,
638 [BPF_ALU | BPF_DIV | BPF_K] = true,
639 [BPF_ALU | BPF_DIV | BPF_X] = true,
640 [BPF_ALU | BPF_MOD | BPF_K] = true,
641 [BPF_ALU | BPF_MOD | BPF_X] = true,
642 [BPF_ALU | BPF_AND | BPF_K] = true,
643 [BPF_ALU | BPF_AND | BPF_X] = true,
644 [BPF_ALU | BPF_OR | BPF_K] = true,
645 [BPF_ALU | BPF_OR | BPF_X] = true,
646 [BPF_ALU | BPF_XOR | BPF_K] = true,
647 [BPF_ALU | BPF_XOR | BPF_X] = true,
648 [BPF_ALU | BPF_LSH | BPF_K] = true,
649 [BPF_ALU | BPF_LSH | BPF_X] = true,
650 [BPF_ALU | BPF_RSH | BPF_K] = true,
651 [BPF_ALU | BPF_RSH | BPF_X] = true,
652 [BPF_ALU | BPF_NEG] = true,
653 /* Load instructions */
654 [BPF_LD | BPF_W | BPF_ABS] = true,
655 [BPF_LD | BPF_H | BPF_ABS] = true,
656 [BPF_LD | BPF_B | BPF_ABS] = true,
657 [BPF_LD | BPF_W | BPF_LEN] = true,
658 [BPF_LD | BPF_W | BPF_IND] = true,
659 [BPF_LD | BPF_H | BPF_IND] = true,
660 [BPF_LD | BPF_B | BPF_IND] = true,
661 [BPF_LD | BPF_IMM] = true,
662 [BPF_LD | BPF_MEM] = true,
663 [BPF_LDX | BPF_W | BPF_LEN] = true,
664 [BPF_LDX | BPF_B | BPF_MSH] = true,
665 [BPF_LDX | BPF_IMM] = true,
666 [BPF_LDX | BPF_MEM] = true,
667 /* Store instructions */
668 [BPF_ST] = true,
669 [BPF_STX] = true,
670 /* Misc instructions */
671 [BPF_MISC | BPF_TAX] = true,
672 [BPF_MISC | BPF_TXA] = true,
673 /* Return instructions */
674 [BPF_RET | BPF_K] = true,
675 [BPF_RET | BPF_A] = true,
676 /* Jump instructions */
677 [BPF_JMP | BPF_JA] = true,
678 [BPF_JMP | BPF_JEQ | BPF_K] = true,
679 [BPF_JMP | BPF_JEQ | BPF_X] = true,
680 [BPF_JMP | BPF_JGE | BPF_K] = true,
681 [BPF_JMP | BPF_JGE | BPF_X] = true,
682 [BPF_JMP | BPF_JGT | BPF_K] = true,
683 [BPF_JMP | BPF_JGT | BPF_X] = true,
684 [BPF_JMP | BPF_JSET | BPF_K] = true,
685 [BPF_JMP | BPF_JSET | BPF_X] = true,
686 };
687
688 if (code_to_probe >= ARRAY_SIZE(codes))
689 return false;
690
691 return codes[code_to_probe];
692 }
693
694 /**
695 * bpf_check_classic - verify socket filter code
696 * @filter: filter to verify
697 * @flen: length of filter
698 *
699 * Check the user's filter code. If we let some ugly
700 * filter code slip through kaboom! The filter must contain
701 * no references or jumps that are out of range, no illegal
702 * instructions, and must end with a RET instruction.
703 *
704 * All jumps are forward as they are not signed.
705 *
706 * Returns 0 if the rule set is legal or -EINVAL if not.
707 */
708 int bpf_check_classic(const struct sock_filter *filter, unsigned int flen)
709 {
710 bool anc_found;
711 int pc;
712
713 if (flen == 0 || flen > BPF_MAXINSNS)
714 return -EINVAL;
715
716 /* Check the filter code now */
717 for (pc = 0; pc < flen; pc++) {
718 const struct sock_filter *ftest = &filter[pc];
719
720 /* May we actually operate on this code? */
721 if (!chk_code_allowed(ftest->code))
722 return -EINVAL;
723
724 /* Some instructions need special checks */
725 switch (ftest->code) {
726 case BPF_ALU | BPF_DIV | BPF_K:
727 case BPF_ALU | BPF_MOD | BPF_K:
728 /* Check for division by zero */
729 if (ftest->k == 0)
730 return -EINVAL;
731 break;
732 case BPF_LD | BPF_MEM:
733 case BPF_LDX | BPF_MEM:
734 case BPF_ST:
735 case BPF_STX:
736 /* Check for invalid memory addresses */
737 if (ftest->k >= BPF_MEMWORDS)
738 return -EINVAL;
739 break;
740 case BPF_JMP | BPF_JA:
741 /* Note, the large ftest->k might cause loops.
742 * Compare this with conditional jumps below,
743 * where offsets are limited. --ANK (981016)
744 */
745 if (ftest->k >= (unsigned int)(flen - pc - 1))
746 return -EINVAL;
747 break;
748 case BPF_JMP | BPF_JEQ | BPF_K:
749 case BPF_JMP | BPF_JEQ | BPF_X:
750 case BPF_JMP | BPF_JGE | BPF_K:
751 case BPF_JMP | BPF_JGE | BPF_X:
752 case BPF_JMP | BPF_JGT | BPF_K:
753 case BPF_JMP | BPF_JGT | BPF_X:
754 case BPF_JMP | BPF_JSET | BPF_K:
755 case BPF_JMP | BPF_JSET | BPF_X:
756 /* Both conditionals must be safe */
757 if (pc + ftest->jt + 1 >= flen ||
758 pc + ftest->jf + 1 >= flen)
759 return -EINVAL;
760 break;
761 case BPF_LD | BPF_W | BPF_ABS:
762 case BPF_LD | BPF_H | BPF_ABS:
763 case BPF_LD | BPF_B | BPF_ABS:
764 anc_found = false;
765 if (bpf_anc_helper(ftest) & BPF_ANC)
766 anc_found = true;
767 /* Ancillary operation unknown or unsupported */
768 if (anc_found == false && ftest->k >= SKF_AD_OFF)
769 return -EINVAL;
770 }
771 }
772
773 /* Last instruction must be a RET code */
774 switch (filter[flen - 1].code) {
775 case BPF_RET | BPF_K:
776 case BPF_RET | BPF_A:
777 return check_load_and_stores(filter, flen);
778 }
779
780 return -EINVAL;
781 }
782 EXPORT_SYMBOL(bpf_check_classic);
783
784 static int bpf_prog_store_orig_filter(struct bpf_prog *fp,
785 const struct sock_fprog *fprog)
786 {
787 unsigned int fsize = bpf_classic_proglen(fprog);
788 struct sock_fprog_kern *fkprog;
789
790 fp->orig_prog = kmalloc(sizeof(*fkprog), GFP_KERNEL);
791 if (!fp->orig_prog)
792 return -ENOMEM;
793
794 fkprog = fp->orig_prog;
795 fkprog->len = fprog->len;
796 fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL);
797 if (!fkprog->filter) {
798 kfree(fp->orig_prog);
799 return -ENOMEM;
800 }
801
802 return 0;
803 }
804
805 static void bpf_release_orig_filter(struct bpf_prog *fp)
806 {
807 struct sock_fprog_kern *fprog = fp->orig_prog;
808
809 if (fprog) {
810 kfree(fprog->filter);
811 kfree(fprog);
812 }
813 }
814
815 static void __bpf_prog_release(struct bpf_prog *prog)
816 {
817 if (prog->aux->prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
818 bpf_prog_put(prog);
819 } else {
820 bpf_release_orig_filter(prog);
821 bpf_prog_free(prog);
822 }
823 }
824
825 static void __sk_filter_release(struct sk_filter *fp)
826 {
827 __bpf_prog_release(fp->prog);
828 kfree(fp);
829 }
830
831 /**
832 * sk_filter_release_rcu - Release a socket filter by rcu_head
833 * @rcu: rcu_head that contains the sk_filter to free
834 */
835 static void sk_filter_release_rcu(struct rcu_head *rcu)
836 {
837 struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
838
839 __sk_filter_release(fp);
840 }
841
842 /**
843 * sk_filter_release - release a socket filter
844 * @fp: filter to remove
845 *
846 * Remove a filter from a socket and release its resources.
847 */
848 static void sk_filter_release(struct sk_filter *fp)
849 {
850 if (atomic_dec_and_test(&fp->refcnt))
851 call_rcu(&fp->rcu, sk_filter_release_rcu);
852 }
853
854 void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
855 {
856 u32 filter_size = bpf_prog_size(fp->prog->len);
857
858 atomic_sub(filter_size, &sk->sk_omem_alloc);
859 sk_filter_release(fp);
860 }
861
862 /* try to charge the socket memory if there is space available
863 * return true on success
864 */
865 bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
866 {
867 u32 filter_size = bpf_prog_size(fp->prog->len);
868
869 /* same check as in sock_kmalloc() */
870 if (filter_size <= sysctl_optmem_max &&
871 atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
872 atomic_inc(&fp->refcnt);
873 atomic_add(filter_size, &sk->sk_omem_alloc);
874 return true;
875 }
876 return false;
877 }
878
879 static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
880 {
881 struct sock_filter *old_prog;
882 struct bpf_prog *old_fp;
883 int err, new_len, old_len = fp->len;
884
885 /* We are free to overwrite insns et al right here as it
886 * won't be used at this point in time anymore internally
887 * after the migration to the internal BPF instruction
888 * representation.
889 */
890 BUILD_BUG_ON(sizeof(struct sock_filter) !=
891 sizeof(struct bpf_insn));
892
893 /* Conversion cannot happen on overlapping memory areas,
894 * so we need to keep the user BPF around until the 2nd
895 * pass. At this time, the user BPF is stored in fp->insns.
896 */
897 old_prog = kmemdup(fp->insns, old_len * sizeof(struct sock_filter),
898 GFP_KERNEL);
899 if (!old_prog) {
900 err = -ENOMEM;
901 goto out_err;
902 }
903
904 /* 1st pass: calculate the new program length. */
905 err = bpf_convert_filter(old_prog, old_len, NULL, &new_len);
906 if (err)
907 goto out_err_free;
908
909 /* Expand fp for appending the new filter representation. */
910 old_fp = fp;
911 fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0);
912 if (!fp) {
913 /* The old_fp is still around in case we couldn't
914 * allocate new memory, so uncharge on that one.
915 */
916 fp = old_fp;
917 err = -ENOMEM;
918 goto out_err_free;
919 }
920
921 fp->len = new_len;
922
923 /* 2nd pass: remap sock_filter insns into bpf_insn insns. */
924 err = bpf_convert_filter(old_prog, old_len, fp->insnsi, &new_len);
925 if (err)
926 /* 2nd bpf_convert_filter() can fail only if it fails
927 * to allocate memory, remapping must succeed. Note,
928 * that at this time old_fp has already been released
929 * by krealloc().
930 */
931 goto out_err_free;
932
933 bpf_prog_select_runtime(fp);
934
935 kfree(old_prog);
936 return fp;
937
938 out_err_free:
939 kfree(old_prog);
940 out_err:
941 __bpf_prog_release(fp);
942 return ERR_PTR(err);
943 }
944
945 static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp)
946 {
947 int err;
948
949 fp->bpf_func = NULL;
950 fp->jited = false;
951
952 err = bpf_check_classic(fp->insns, fp->len);
953 if (err) {
954 __bpf_prog_release(fp);
955 return ERR_PTR(err);
956 }
957
958 /* Probe if we can JIT compile the filter and if so, do
959 * the compilation of the filter.
960 */
961 bpf_jit_compile(fp);
962
963 /* JIT compiler couldn't process this filter, so do the
964 * internal BPF translation for the optimized interpreter.
965 */
966 if (!fp->jited)
967 fp = bpf_migrate_filter(fp);
968
969 return fp;
970 }
971
972 /**
973 * bpf_prog_create - create an unattached filter
974 * @pfp: the unattached filter that is created
975 * @fprog: the filter program
976 *
977 * Create a filter independent of any socket. We first run some
978 * sanity checks on it to make sure it does not explode on us later.
979 * If an error occurs or there is insufficient memory for the filter
980 * a negative errno code is returned. On success the return is zero.
981 */
982 int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog)
983 {
984 unsigned int fsize = bpf_classic_proglen(fprog);
985 struct bpf_prog *fp;
986
987 /* Make sure new filter is there and in the right amounts. */
988 if (fprog->filter == NULL)
989 return -EINVAL;
990
991 fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
992 if (!fp)
993 return -ENOMEM;
994
995 memcpy(fp->insns, fprog->filter, fsize);
996
997 fp->len = fprog->len;
998 /* Since unattached filters are not copied back to user
999 * space through sk_get_filter(), we do not need to hold
1000 * a copy here, and can spare us the work.
1001 */
1002 fp->orig_prog = NULL;
1003
1004 /* bpf_prepare_filter() already takes care of freeing
1005 * memory in case something goes wrong.
1006 */
1007 fp = bpf_prepare_filter(fp);
1008 if (IS_ERR(fp))
1009 return PTR_ERR(fp);
1010
1011 *pfp = fp;
1012 return 0;
1013 }
1014 EXPORT_SYMBOL_GPL(bpf_prog_create);
1015
1016 void bpf_prog_destroy(struct bpf_prog *fp)
1017 {
1018 __bpf_prog_release(fp);
1019 }
1020 EXPORT_SYMBOL_GPL(bpf_prog_destroy);
1021
1022 /**
1023 * sk_attach_filter - attach a socket filter
1024 * @fprog: the filter program
1025 * @sk: the socket to use
1026 *
1027 * Attach the user's filter code. We first run some sanity checks on
1028 * it to make sure it does not explode on us later. If an error
1029 * occurs or there is insufficient memory for the filter a negative
1030 * errno code is returned. On success the return is zero.
1031 */
1032 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
1033 {
1034 struct sk_filter *fp, *old_fp;
1035 unsigned int fsize = bpf_classic_proglen(fprog);
1036 unsigned int bpf_fsize = bpf_prog_size(fprog->len);
1037 struct bpf_prog *prog;
1038 int err;
1039
1040 if (sock_flag(sk, SOCK_FILTER_LOCKED))
1041 return -EPERM;
1042
1043 /* Make sure new filter is there and in the right amounts. */
1044 if (fprog->filter == NULL)
1045 return -EINVAL;
1046
1047 prog = bpf_prog_alloc(bpf_fsize, 0);
1048 if (!prog)
1049 return -ENOMEM;
1050
1051 if (copy_from_user(prog->insns, fprog->filter, fsize)) {
1052 __bpf_prog_free(prog);
1053 return -EFAULT;
1054 }
1055
1056 prog->len = fprog->len;
1057
1058 err = bpf_prog_store_orig_filter(prog, fprog);
1059 if (err) {
1060 __bpf_prog_free(prog);
1061 return -ENOMEM;
1062 }
1063
1064 /* bpf_prepare_filter() already takes care of freeing
1065 * memory in case something goes wrong.
1066 */
1067 prog = bpf_prepare_filter(prog);
1068 if (IS_ERR(prog))
1069 return PTR_ERR(prog);
1070
1071 fp = kmalloc(sizeof(*fp), GFP_KERNEL);
1072 if (!fp) {
1073 __bpf_prog_release(prog);
1074 return -ENOMEM;
1075 }
1076 fp->prog = prog;
1077
1078 atomic_set(&fp->refcnt, 0);
1079
1080 if (!sk_filter_charge(sk, fp)) {
1081 __sk_filter_release(fp);
1082 return -ENOMEM;
1083 }
1084
1085 old_fp = rcu_dereference_protected(sk->sk_filter,
1086 sock_owned_by_user(sk));
1087 rcu_assign_pointer(sk->sk_filter, fp);
1088
1089 if (old_fp)
1090 sk_filter_uncharge(sk, old_fp);
1091
1092 return 0;
1093 }
1094 EXPORT_SYMBOL_GPL(sk_attach_filter);
1095
1096 #ifdef CONFIG_BPF_SYSCALL
1097 int sk_attach_bpf(u32 ufd, struct sock *sk)
1098 {
1099 struct sk_filter *fp, *old_fp;
1100 struct bpf_prog *prog;
1101
1102 if (sock_flag(sk, SOCK_FILTER_LOCKED))
1103 return -EPERM;
1104
1105 prog = bpf_prog_get(ufd);
1106 if (IS_ERR(prog))
1107 return PTR_ERR(prog);
1108
1109 if (prog->aux->prog_type != BPF_PROG_TYPE_SOCKET_FILTER) {
1110 /* valid fd, but invalid program type */
1111 bpf_prog_put(prog);
1112 return -EINVAL;
1113 }
1114
1115 fp = kmalloc(sizeof(*fp), GFP_KERNEL);
1116 if (!fp) {
1117 bpf_prog_put(prog);
1118 return -ENOMEM;
1119 }
1120 fp->prog = prog;
1121
1122 atomic_set(&fp->refcnt, 0);
1123
1124 if (!sk_filter_charge(sk, fp)) {
1125 __sk_filter_release(fp);
1126 return -ENOMEM;
1127 }
1128
1129 old_fp = rcu_dereference_protected(sk->sk_filter,
1130 sock_owned_by_user(sk));
1131 rcu_assign_pointer(sk->sk_filter, fp);
1132
1133 if (old_fp)
1134 sk_filter_uncharge(sk, old_fp);
1135
1136 return 0;
1137 }
1138
1139 /* allow socket filters to call
1140 * bpf_map_lookup_elem(), bpf_map_update_elem(), bpf_map_delete_elem()
1141 */
1142 static const struct bpf_func_proto *sock_filter_func_proto(enum bpf_func_id func_id)
1143 {
1144 switch (func_id) {
1145 case BPF_FUNC_map_lookup_elem:
1146 return &bpf_map_lookup_elem_proto;
1147 case BPF_FUNC_map_update_elem:
1148 return &bpf_map_update_elem_proto;
1149 case BPF_FUNC_map_delete_elem:
1150 return &bpf_map_delete_elem_proto;
1151 default:
1152 return NULL;
1153 }
1154 }
1155
1156 static bool sock_filter_is_valid_access(int off, int size, enum bpf_access_type type)
1157 {
1158 /* skb fields cannot be accessed yet */
1159 return false;
1160 }
1161
1162 static struct bpf_verifier_ops sock_filter_ops = {
1163 .get_func_proto = sock_filter_func_proto,
1164 .is_valid_access = sock_filter_is_valid_access,
1165 };
1166
1167 static struct bpf_prog_type_list tl = {
1168 .ops = &sock_filter_ops,
1169 .type = BPF_PROG_TYPE_SOCKET_FILTER,
1170 };
1171
1172 static int __init register_sock_filter_ops(void)
1173 {
1174 bpf_register_prog_type(&tl);
1175 return 0;
1176 }
1177 late_initcall(register_sock_filter_ops);
1178 #else
1179 int sk_attach_bpf(u32 ufd, struct sock *sk)
1180 {
1181 return -EOPNOTSUPP;
1182 }
1183 #endif
1184 int sk_detach_filter(struct sock *sk)
1185 {
1186 int ret = -ENOENT;
1187 struct sk_filter *filter;
1188
1189 if (sock_flag(sk, SOCK_FILTER_LOCKED))
1190 return -EPERM;
1191
1192 filter = rcu_dereference_protected(sk->sk_filter,
1193 sock_owned_by_user(sk));
1194 if (filter) {
1195 RCU_INIT_POINTER(sk->sk_filter, NULL);
1196 sk_filter_uncharge(sk, filter);
1197 ret = 0;
1198 }
1199
1200 return ret;
1201 }
1202 EXPORT_SYMBOL_GPL(sk_detach_filter);
1203
1204 int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
1205 unsigned int len)
1206 {
1207 struct sock_fprog_kern *fprog;
1208 struct sk_filter *filter;
1209 int ret = 0;
1210
1211 lock_sock(sk);
1212 filter = rcu_dereference_protected(sk->sk_filter,
1213 sock_owned_by_user(sk));
1214 if (!filter)
1215 goto out;
1216
1217 /* We're copying the filter that has been originally attached,
1218 * so no conversion/decode needed anymore.
1219 */
1220 fprog = filter->prog->orig_prog;
1221
1222 ret = fprog->len;
1223 if (!len)
1224 /* User space only enquires number of filter blocks. */
1225 goto out;
1226
1227 ret = -EINVAL;
1228 if (len < fprog->len)
1229 goto out;
1230
1231 ret = -EFAULT;
1232 if (copy_to_user(ubuf, fprog->filter, bpf_classic_proglen(fprog)))
1233 goto out;
1234
1235 /* Instead of bytes, the API requests to return the number
1236 * of filter blocks.
1237 */
1238 ret = fprog->len;
1239 out:
1240 release_sock(sk);
1241 return ret;
1242 }
(deprecated) Btrfs devel tree