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