projects/linux·blob v4.3 · refs

663 lines · 14.3 KiB

1/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * This program is distributed in the hope that it will be useful, but
8 * WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
10 * General Public License for more details.
11 */
12#include <linux/bpf.h>
13#include <linux/syscalls.h>
14#include <linux/slab.h>
15#include <linux/anon_inodes.h>
16#include <linux/file.h>
17#include <linux/license.h>
18#include <linux/filter.h>
19#include <linux/version.h>
20
21static LIST_HEAD(bpf_map_types);
22
23static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
24{
25 struct bpf_map_type_list *tl;
26 struct bpf_map *map;
27
28 list_for_each_entry(tl, &bpf_map_types, list_node) {
29 if (tl->type == attr->map_type) {
30 map = tl->ops->map_alloc(attr);
31 if (IS_ERR(map))
32 return map;
33 map->ops = tl->ops;
34 map->map_type = attr->map_type;
35 return map;
36 }
37 }
38 return ERR_PTR(-EINVAL);
39}
40
41/* boot time registration of different map implementations */
42void bpf_register_map_type(struct bpf_map_type_list *tl)
43{
44 list_add(&tl->list_node, &bpf_map_types);
45}
46
47/* called from workqueue */
48static void bpf_map_free_deferred(struct work_struct *work)
49{
50 struct bpf_map *map = container_of(work, struct bpf_map, work);
51
52 /* implementation dependent freeing */
53 map->ops->map_free(map);
54}
55
56/* decrement map refcnt and schedule it for freeing via workqueue
57 * (unrelying map implementation ops->map_free() might sleep)
58 */
59void bpf_map_put(struct bpf_map *map)
60{
61 if (atomic_dec_and_test(&map->refcnt)) {
62 INIT_WORK(&map->work, bpf_map_free_deferred);
63 schedule_work(&map->work);
64 }
65}
66
67static int bpf_map_release(struct inode *inode, struct file *filp)
68{
69 struct bpf_map *map = filp->private_data;
70
71 if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY)
72 /* prog_array stores refcnt-ed bpf_prog pointers
73 * release them all when user space closes prog_array_fd
74 */
75 bpf_fd_array_map_clear(map);
76
77 bpf_map_put(map);
78 return 0;
79}
80
81static const struct file_operations bpf_map_fops = {
82 .release = bpf_map_release,
83};
84
85/* helper macro to check that unused fields 'union bpf_attr' are zero */
86#define CHECK_ATTR(CMD) \
87 memchr_inv((void *) &attr->CMD##_LAST_FIELD + \
88 sizeof(attr->CMD##_LAST_FIELD), 0, \
89 sizeof(*attr) - \
90 offsetof(union bpf_attr, CMD##_LAST_FIELD) - \
91 sizeof(attr->CMD##_LAST_FIELD)) != NULL
92
93#define BPF_MAP_CREATE_LAST_FIELD max_entries
94/* called via syscall */
95static int map_create(union bpf_attr *attr)
96{
97 struct bpf_map *map;
98 int err;
99
100 err = CHECK_ATTR(BPF_MAP_CREATE);
101 if (err)
102 return -EINVAL;
103
104 /* find map type and init map: hashtable vs rbtree vs bloom vs ... */
105 map = find_and_alloc_map(attr);
106 if (IS_ERR(map))
107 return PTR_ERR(map);
108
109 atomic_set(&map->refcnt, 1);
110
111 err = anon_inode_getfd("bpf-map", &bpf_map_fops, map, O_RDWR | O_CLOEXEC);
112
113 if (err < 0)
114 /* failed to allocate fd */
115 goto free_map;
116
117 return err;
118
119free_map:
120 map->ops->map_free(map);
121 return err;
122}
123
124/* if error is returned, fd is released.
125 * On success caller should complete fd access with matching fdput()
126 */
127struct bpf_map *bpf_map_get(struct fd f)
128{
129 struct bpf_map *map;
130
131 if (!f.file)
132 return ERR_PTR(-EBADF);
133
134 if (f.file->f_op != &bpf_map_fops) {
135 fdput(f);
136 return ERR_PTR(-EINVAL);
137 }
138
139 map = f.file->private_data;
140
141 return map;
142}
143
144/* helper to convert user pointers passed inside __aligned_u64 fields */
145static void __user *u64_to_ptr(__u64 val)
146{
147 return (void __user *) (unsigned long) val;
148}
149
150/* last field in 'union bpf_attr' used by this command */
151#define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value
152
153static int map_lookup_elem(union bpf_attr *attr)
154{
155 void __user *ukey = u64_to_ptr(attr->key);
156 void __user *uvalue = u64_to_ptr(attr->value);
157 int ufd = attr->map_fd;
158 struct bpf_map *map;
159 void *key, *value, *ptr;
160 struct fd f;
161 int err;
162
163 if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
164 return -EINVAL;
165
166 f = fdget(ufd);
167 map = bpf_map_get(f);
168 if (IS_ERR(map))
169 return PTR_ERR(map);
170
171 err = -ENOMEM;
172 key = kmalloc(map->key_size, GFP_USER);
173 if (!key)
174 goto err_put;
175
176 err = -EFAULT;
177 if (copy_from_user(key, ukey, map->key_size) != 0)
178 goto free_key;
179
180 err = -ENOMEM;
181 value = kmalloc(map->value_size, GFP_USER);
182 if (!value)
183 goto free_key;
184
185 rcu_read_lock();
186 ptr = map->ops->map_lookup_elem(map, key);
187 if (ptr)
188 memcpy(value, ptr, map->value_size);
189 rcu_read_unlock();
190
191 err = -ENOENT;
192 if (!ptr)
193 goto free_value;
194
195 err = -EFAULT;
196 if (copy_to_user(uvalue, value, map->value_size) != 0)
197 goto free_value;
198
199 err = 0;
200
201free_value:
202 kfree(value);
203free_key:
204 kfree(key);
205err_put:
206 fdput(f);
207 return err;
208}
209
210#define BPF_MAP_UPDATE_ELEM_LAST_FIELD flags
211
212static int map_update_elem(union bpf_attr *attr)
213{
214 void __user *ukey = u64_to_ptr(attr->key);
215 void __user *uvalue = u64_to_ptr(attr->value);
216 int ufd = attr->map_fd;
217 struct bpf_map *map;
218 void *key, *value;
219 struct fd f;
220 int err;
221
222 if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
223 return -EINVAL;
224
225 f = fdget(ufd);
226 map = bpf_map_get(f);
227 if (IS_ERR(map))
228 return PTR_ERR(map);
229
230 err = -ENOMEM;
231 key = kmalloc(map->key_size, GFP_USER);
232 if (!key)
233 goto err_put;
234
235 err = -EFAULT;
236 if (copy_from_user(key, ukey, map->key_size) != 0)
237 goto free_key;
238
239 err = -ENOMEM;
240 value = kmalloc(map->value_size, GFP_USER);
241 if (!value)
242 goto free_key;
243
244 err = -EFAULT;
245 if (copy_from_user(value, uvalue, map->value_size) != 0)
246 goto free_value;
247
248 /* eBPF program that use maps are running under rcu_read_lock(),
249 * therefore all map accessors rely on this fact, so do the same here
250 */
251 rcu_read_lock();
252 err = map->ops->map_update_elem(map, key, value, attr->flags);
253 rcu_read_unlock();
254
255free_value:
256 kfree(value);
257free_key:
258 kfree(key);
259err_put:
260 fdput(f);
261 return err;
262}
263
264#define BPF_MAP_DELETE_ELEM_LAST_FIELD key
265
266static int map_delete_elem(union bpf_attr *attr)
267{
268 void __user *ukey = u64_to_ptr(attr->key);
269 int ufd = attr->map_fd;
270 struct bpf_map *map;
271 struct fd f;
272 void *key;
273 int err;
274
275 if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
276 return -EINVAL;
277
278 f = fdget(ufd);
279 map = bpf_map_get(f);
280 if (IS_ERR(map))
281 return PTR_ERR(map);
282
283 err = -ENOMEM;
284 key = kmalloc(map->key_size, GFP_USER);
285 if (!key)
286 goto err_put;
287
288 err = -EFAULT;
289 if (copy_from_user(key, ukey, map->key_size) != 0)
290 goto free_key;
291
292 rcu_read_lock();
293 err = map->ops->map_delete_elem(map, key);
294 rcu_read_unlock();
295
296free_key:
297 kfree(key);
298err_put:
299 fdput(f);
300 return err;
301}
302
303/* last field in 'union bpf_attr' used by this command */
304#define BPF_MAP_GET_NEXT_KEY_LAST_FIELD next_key
305
306static int map_get_next_key(union bpf_attr *attr)
307{
308 void __user *ukey = u64_to_ptr(attr->key);
309 void __user *unext_key = u64_to_ptr(attr->next_key);
310 int ufd = attr->map_fd;
311 struct bpf_map *map;
312 void *key, *next_key;
313 struct fd f;
314 int err;
315
316 if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
317 return -EINVAL;
318
319 f = fdget(ufd);
320 map = bpf_map_get(f);
321 if (IS_ERR(map))
322 return PTR_ERR(map);
323
324 err = -ENOMEM;
325 key = kmalloc(map->key_size, GFP_USER);
326 if (!key)
327 goto err_put;
328
329 err = -EFAULT;
330 if (copy_from_user(key, ukey, map->key_size) != 0)
331 goto free_key;
332
333 err = -ENOMEM;
334 next_key = kmalloc(map->key_size, GFP_USER);
335 if (!next_key)
336 goto free_key;
337
338 rcu_read_lock();
339 err = map->ops->map_get_next_key(map, key, next_key);
340 rcu_read_unlock();
341 if (err)
342 goto free_next_key;
343
344 err = -EFAULT;
345 if (copy_to_user(unext_key, next_key, map->key_size) != 0)
346 goto free_next_key;
347
348 err = 0;
349
350free_next_key:
351 kfree(next_key);
352free_key:
353 kfree(key);
354err_put:
355 fdput(f);
356 return err;
357}
358
359static LIST_HEAD(bpf_prog_types);
360
361static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
362{
363 struct bpf_prog_type_list *tl;
364
365 list_for_each_entry(tl, &bpf_prog_types, list_node) {
366 if (tl->type == type) {
367 prog->aux->ops = tl->ops;
368 prog->type = type;
369 return 0;
370 }
371 }
372
373 return -EINVAL;
374}
375
376void bpf_register_prog_type(struct bpf_prog_type_list *tl)
377{
378 list_add(&tl->list_node, &bpf_prog_types);
379}
380
381/* fixup insn->imm field of bpf_call instructions:
382 * if (insn->imm == BPF_FUNC_map_lookup_elem)
383 * insn->imm = bpf_map_lookup_elem - __bpf_call_base;
384 * else if (insn->imm == BPF_FUNC_map_update_elem)
385 * insn->imm = bpf_map_update_elem - __bpf_call_base;
386 * else ...
387 *
388 * this function is called after eBPF program passed verification
389 */
390static void fixup_bpf_calls(struct bpf_prog *prog)
391{
392 const struct bpf_func_proto *fn;
393 int i;
394
395 for (i = 0; i < prog->len; i++) {
396 struct bpf_insn *insn = &prog->insnsi[i];
397
398 if (insn->code == (BPF_JMP | BPF_CALL)) {
399 /* we reach here when program has bpf_call instructions
400 * and it passed bpf_check(), means that
401 * ops->get_func_proto must have been supplied, check it
402 */
403 BUG_ON(!prog->aux->ops->get_func_proto);
404
405 if (insn->imm == BPF_FUNC_tail_call) {
406 /* mark bpf_tail_call as different opcode
407 * to avoid conditional branch in
408 * interpeter for every normal call
409 * and to prevent accidental JITing by
410 * JIT compiler that doesn't support
411 * bpf_tail_call yet
412 */
413 insn->imm = 0;
414 insn->code |= BPF_X;
415 continue;
416 }
417
418 fn = prog->aux->ops->get_func_proto(insn->imm);
419 /* all functions that have prototype and verifier allowed
420 * programs to call them, must be real in-kernel functions
421 */
422 BUG_ON(!fn->func);
423 insn->imm = fn->func - __bpf_call_base;
424 }
425 }
426}
427
428/* drop refcnt on maps used by eBPF program and free auxilary data */
429static void free_used_maps(struct bpf_prog_aux *aux)
430{
431 int i;
432
433 for (i = 0; i < aux->used_map_cnt; i++)
434 bpf_map_put(aux->used_maps[i]);
435
436 kfree(aux->used_maps);
437}
438
439static void __prog_put_rcu(struct rcu_head *rcu)
440{
441 struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
442
443 free_used_maps(aux);
444 bpf_prog_free(aux->prog);
445}
446
447/* version of bpf_prog_put() that is called after a grace period */
448void bpf_prog_put_rcu(struct bpf_prog *prog)
449{
450 if (atomic_dec_and_test(&prog->aux->refcnt)) {
451 prog->aux->prog = prog;
452 call_rcu(&prog->aux->rcu, __prog_put_rcu);
453 }
454}
455
456void bpf_prog_put(struct bpf_prog *prog)
457{
458 if (atomic_dec_and_test(&prog->aux->refcnt)) {
459 free_used_maps(prog->aux);
460 bpf_prog_free(prog);
461 }
462}
463EXPORT_SYMBOL_GPL(bpf_prog_put);
464
465static int bpf_prog_release(struct inode *inode, struct file *filp)
466{
467 struct bpf_prog *prog = filp->private_data;
468
469 bpf_prog_put_rcu(prog);
470 return 0;
471}
472
473static const struct file_operations bpf_prog_fops = {
474 .release = bpf_prog_release,
475};
476
477static struct bpf_prog *get_prog(struct fd f)
478{
479 struct bpf_prog *prog;
480
481 if (!f.file)
482 return ERR_PTR(-EBADF);
483
484 if (f.file->f_op != &bpf_prog_fops) {
485 fdput(f);
486 return ERR_PTR(-EINVAL);
487 }
488
489 prog = f.file->private_data;
490
491 return prog;
492}
493
494/* called by sockets/tracing/seccomp before attaching program to an event
495 * pairs with bpf_prog_put()
496 */
497struct bpf_prog *bpf_prog_get(u32 ufd)
498{
499 struct fd f = fdget(ufd);
500 struct bpf_prog *prog;
501
502 prog = get_prog(f);
503
504 if (IS_ERR(prog))
505 return prog;
506
507 atomic_inc(&prog->aux->refcnt);
508 fdput(f);
509 return prog;
510}
511EXPORT_SYMBOL_GPL(bpf_prog_get);
512
513/* last field in 'union bpf_attr' used by this command */
514#define BPF_PROG_LOAD_LAST_FIELD kern_version
515
516static int bpf_prog_load(union bpf_attr *attr)
517{
518 enum bpf_prog_type type = attr->prog_type;
519 struct bpf_prog *prog;
520 int err;
521 char license[128];
522 bool is_gpl;
523
524 if (CHECK_ATTR(BPF_PROG_LOAD))
525 return -EINVAL;
526
527 /* copy eBPF program license from user space */
528 if (strncpy_from_user(license, u64_to_ptr(attr->license),
529 sizeof(license) - 1) < 0)
530 return -EFAULT;
531 license[sizeof(license) - 1] = 0;
532
533 /* eBPF programs must be GPL compatible to use GPL-ed functions */
534 is_gpl = license_is_gpl_compatible(license);
535
536 if (attr->insn_cnt >= BPF_MAXINSNS)
537 return -EINVAL;
538
539 if (type == BPF_PROG_TYPE_KPROBE &&
540 attr->kern_version != LINUX_VERSION_CODE)
541 return -EINVAL;
542
543 /* plain bpf_prog allocation */
544 prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
545 if (!prog)
546 return -ENOMEM;
547
548 prog->len = attr->insn_cnt;
549
550 err = -EFAULT;
551 if (copy_from_user(prog->insns, u64_to_ptr(attr->insns),
552 prog->len * sizeof(struct bpf_insn)) != 0)
553 goto free_prog;
554
555 prog->orig_prog = NULL;
556 prog->jited = false;
557
558 atomic_set(&prog->aux->refcnt, 1);
559 prog->gpl_compatible = is_gpl;
560
561 /* find program type: socket_filter vs tracing_filter */
562 err = find_prog_type(type, prog);
563 if (err < 0)
564 goto free_prog;
565
566 /* run eBPF verifier */
567 err = bpf_check(&prog, attr);
568 if (err < 0)
569 goto free_used_maps;
570
571 /* fixup BPF_CALL->imm field */
572 fixup_bpf_calls(prog);
573
574 /* eBPF program is ready to be JITed */
575 err = bpf_prog_select_runtime(prog);
576 if (err < 0)
577 goto free_used_maps;
578
579 err = anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog, O_RDWR | O_CLOEXEC);
580 if (err < 0)
581 /* failed to allocate fd */
582 goto free_used_maps;
583
584 return err;
585
586free_used_maps:
587 free_used_maps(prog->aux);
588free_prog:
589 bpf_prog_free(prog);
590 return err;
591}
592
593SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
594{
595 union bpf_attr attr = {};
596 int err;
597
598 /* the syscall is limited to root temporarily. This restriction will be
599 * lifted when security audit is clean. Note that eBPF+tracing must have
600 * this restriction, since it may pass kernel data to user space
601 */
602 if (!capable(CAP_SYS_ADMIN))
603 return -EPERM;
604
605 if (!access_ok(VERIFY_READ, uattr, 1))
606 return -EFAULT;
607
608 if (size > PAGE_SIZE) /* silly large */
609 return -E2BIG;
610
611 /* If we're handed a bigger struct than we know of,
612 * ensure all the unknown bits are 0 - i.e. new
613 * user-space does not rely on any kernel feature
614 * extensions we dont know about yet.
615 */
616 if (size > sizeof(attr)) {
617 unsigned char __user *addr;
618 unsigned char __user *end;
619 unsigned char val;
620
621 addr = (void __user *)uattr + sizeof(attr);
622 end = (void __user *)uattr + size;
623
624 for (; addr < end; addr++) {
625 err = get_user(val, addr);
626 if (err)
627 return err;
628 if (val)
629 return -E2BIG;
630 }
631 size = sizeof(attr);
632 }
633
634 /* copy attributes from user space, may be less than sizeof(bpf_attr) */
635 if (copy_from_user(&attr, uattr, size) != 0)
636 return -EFAULT;
637
638 switch (cmd) {
639 case BPF_MAP_CREATE:
640 err = map_create(&attr);
641 break;
642 case BPF_MAP_LOOKUP_ELEM:
643 err = map_lookup_elem(&attr);
644 break;
645 case BPF_MAP_UPDATE_ELEM:
646 err = map_update_elem(&attr);
647 break;
648 case BPF_MAP_DELETE_ELEM:
649 err = map_delete_elem(&attr);
650 break;
651 case BPF_MAP_GET_NEXT_KEY:
652 err = map_get_next_key(&attr);
653 break;
654 case BPF_PROG_LOAD:
655 err = bpf_prog_load(&attr);
656 break;
657 default:
658 err = -EINVAL;
659 break;
660 }
661
662 return err;
663}