aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/bpf/inode.c
blob: dc9d7ac8228db065617004e49cbd621de6ee5fb1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
/*
 * Minimal file system backend for holding eBPF maps and programs,
 * used by bpf(2) object pinning.
 *
 * Authors:
 *
 *	Daniel Borkmann <daniel@iogearbox.net>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/magic.h>
#include <linux/major.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/parser.h>
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/bpf_trace.h>

enum bpf_type {
	BPF_TYPE_UNSPEC	= 0,
	BPF_TYPE_PROG,
	BPF_TYPE_MAP,
};

static void *bpf_any_get(void *raw, enum bpf_type type)
{
	switch (type) {
	case BPF_TYPE_PROG:
		raw = bpf_prog_inc(raw);
		break;
	case BPF_TYPE_MAP:
		raw = bpf_map_inc(raw, true);
		break;
	default:
		WARN_ON_ONCE(1);
		break;
	}

	return raw;
}

static void bpf_any_put(void *raw, enum bpf_type type)
{
	switch (type) {
	case BPF_TYPE_PROG:
		bpf_prog_put(raw);
		break;
	case BPF_TYPE_MAP:
		bpf_map_put_with_uref(raw);
		break;
	default:
		WARN_ON_ONCE(1);
		break;
	}
}

static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
{
	void *raw;

	*type = BPF_TYPE_MAP;
	raw = bpf_map_get_with_uref(ufd);
	if (IS_ERR(raw)) {
		*type = BPF_TYPE_PROG;
		raw = bpf_prog_get(ufd);
	}

	return raw;
}

static const struct inode_operations bpf_dir_iops;

static const struct inode_operations bpf_prog_iops = { };
static const struct inode_operations bpf_map_iops  = { };

static struct inode *bpf_get_inode(struct super_block *sb,
				   const struct inode *dir,
				   umode_t mode)
{
	struct inode *inode;

	switch (mode & S_IFMT) {
	case S_IFDIR:
	case S_IFREG:
	case S_IFLNK:
		break;
	default:
		return ERR_PTR(-EINVAL);
	}

	inode = new_inode(sb);
	if (!inode)
		return ERR_PTR(-ENOSPC);

	inode->i_ino = get_next_ino();
	inode->i_atime = current_time(inode);
	inode->i_mtime = inode->i_atime;
	inode->i_ctime = inode->i_atime;

	inode_init_owner(inode, dir, mode);

	return inode;
}

static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
{
	*type = BPF_TYPE_UNSPEC;
	if (inode->i_op == &bpf_prog_iops)
		*type = BPF_TYPE_PROG;
	else if (inode->i_op == &bpf_map_iops)
		*type = BPF_TYPE_MAP;
	else
		return -EACCES;

	return 0;
}

static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode,
				struct inode *dir)
{
	d_instantiate(dentry, inode);
	dget(dentry);

	dir->i_mtime = current_time(dir);
	dir->i_ctime = dir->i_mtime;
}

static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
	struct inode *inode;

	inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
	if (IS_ERR(inode))
		return PTR_ERR(inode);

	inode->i_op = &bpf_dir_iops;
	inode->i_fop = &simple_dir_operations;

	inc_nlink(inode);
	inc_nlink(dir);

	bpf_dentry_finalize(dentry, inode, dir);
	return 0;
}

struct map_iter {
	void *key;
	bool done;
};

static struct map_iter *map_iter(struct seq_file *m)
{
	return m->private;
}

static struct bpf_map *seq_file_to_map(struct seq_file *m)
{
	return file_inode(m->file)->i_private;
}

static void map_iter_free(struct map_iter *iter)
{
	if (iter) {
		kfree(iter->key);
		kfree(iter);
	}
}

static struct map_iter *map_iter_alloc(struct bpf_map *map)
{
	struct map_iter *iter;

	iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN);
	if (!iter)
		goto error;

	iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN);
	if (!iter->key)
		goto error;

	return iter;

error:
	map_iter_free(iter);
	return NULL;
}

static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct bpf_map *map = seq_file_to_map(m);
	void *key = map_iter(m)->key;
	void *prev_key;

	if (map_iter(m)->done)
		return NULL;

	if (unlikely(v == SEQ_START_TOKEN))
		prev_key = NULL;
	else
		prev_key = key;

	if (map->ops->map_get_next_key(map, prev_key, key)) {
		map_iter(m)->done = true;
		return NULL;
	}

	++(*pos);
	return key;
}

static void *map_seq_start(struct seq_file *m, loff_t *pos)
{
	if (map_iter(m)->done)
		return NULL;

	return *pos ? map_iter(m)->key : SEQ_START_TOKEN;
}

static void map_seq_stop(struct seq_file *m, void *v)
{
}

static int map_seq_show(struct seq_file *m, void *v)
{
	struct bpf_map *map = seq_file_to_map(m);
	void *key = map_iter(m)->key;

	if (unlikely(v == SEQ_START_TOKEN)) {
		seq_puts(m, "# WARNING!! The output is for debug purpose only\n");
		seq_puts(m, "# WARNING!! The output format will change\n");
	} else {
		map->ops->map_seq_show_elem(map, key, m);
	}

	return 0;
}

static const struct seq_operations bpffs_map_seq_ops = {
	.start	= map_seq_start,
	.next	= map_seq_next,
	.show	= map_seq_show,
	.stop	= map_seq_stop,
};

static int bpffs_map_open(struct inode *inode, struct file *file)
{
	struct bpf_map *map = inode->i_private;
	struct map_iter *iter;
	struct seq_file *m;
	int err;

	iter = map_iter_alloc(map);
	if (!iter)
		return -ENOMEM;

	err = seq_open(file, &bpffs_map_seq_ops);
	if (err) {
		map_iter_free(iter);
		return err;
	}

	m = file->private_data;
	m->private = iter;

	return 0;
}

static int bpffs_map_release(struct inode *inode, struct file *file)
{
	struct seq_file *m = file->private_data;

	map_iter_free(map_iter(m));

	return seq_release(inode, file);
}

/* bpffs_map_fops should only implement the basic
 * read operation for a BPF map.  The purpose is to
 * provide a simple user intuitive way to do
 * "cat bpffs/pathto/a-pinned-map".
 *
 * Other operations (e.g. write, lookup...) should be realized by
 * the userspace tools (e.g. bpftool) through the
 * BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update
 * interface.
 */
static const struct file_operations bpffs_map_fops = {
	.open		= bpffs_map_open,
	.read		= seq_read,
	.release	= bpffs_map_release,
};

static int bpffs_obj_open(struct inode *inode, struct file *file)
{
	return -EIO;
}

static const struct file_operations bpffs_obj_fops = {
	.open		= bpffs_obj_open,
};

static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
			 const struct inode_operations *iops,
			 const struct file_operations *fops)
{
	struct inode *dir = dentry->d_parent->d_inode;
	struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode);
	if (IS_ERR(inode))
		return PTR_ERR(inode);

	inode->i_op = iops;
	inode->i_fop = fops;
	inode->i_private = raw;

	bpf_dentry_finalize(dentry, inode, dir);
	return 0;
}

static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)
{
	return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,
			     &bpffs_obj_fops);
}

static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
{
	struct bpf_map *map = arg;

	return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,
			     bpf_map_support_seq_show(map) ?
			     &bpffs_map_fops : &bpffs_obj_fops);
}

static struct dentry *
bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
{
	/* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future
	 * extensions.
	 */
	if (strchr(dentry->d_name.name, '.'))
		return ERR_PTR(-EPERM);

	return simple_lookup(dir, dentry, flags);
}

static int bpf_symlink(struct inode *dir, struct dentry *dentry,
		       const char *target)
{
	char *link = kstrdup(target, GFP_USER | __GFP_NOWARN);
	struct inode *inode;

	if (!link)
		return -ENOMEM;

	inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK);
	if (IS_ERR(inode)) {
		kfree(link);
		return PTR_ERR(inode);
	}

	inode->i_op = &simple_symlink_inode_operations;
	inode->i_link = link;

	bpf_dentry_finalize(dentry, inode, dir);
	return 0;
}

static const struct inode_operations bpf_dir_iops = {
	.lookup		= bpf_lookup,
	.mkdir		= bpf_mkdir,
	.symlink	= bpf_symlink,
	.rmdir		= simple_rmdir,
	.rename		= simple_rename,
	.link		= simple_link,
	.unlink		= simple_unlink,
};

static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
			  enum bpf_type type)
{
	struct dentry *dentry;
	struct inode *dir;
	struct path path;
	umode_t mode;
	int ret;

	dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());

	ret = security_path_mknod(&path, dentry, mode, 0);
	if (ret)
		goto out;

	dir = d_inode(path.dentry);
	if (dir->i_op != &bpf_dir_iops) {
		ret = -EPERM;
		goto out;
	}

	switch (type) {
	case BPF_TYPE_PROG:
		ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw);
		break;
	case BPF_TYPE_MAP:
		ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);
		break;
	default:
		ret = -EPERM;
	}
out:
	done_path_create(&path, dentry);
	return ret;
}

int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
{
	struct filename *pname;
	enum bpf_type type;
	void *raw;
	int ret;

	pname = getname(pathname);
	if (IS_ERR(pname))
		return PTR_ERR(pname);

	raw = bpf_fd_probe_obj(ufd, &type);
	if (IS_ERR(raw)) {
		ret = PTR_ERR(raw);
		goto out;
	}

	ret = bpf_obj_do_pin(pname, raw, type);
	if (ret != 0)
		bpf_any_put(raw, type);
out:
	putname(pname);
	return ret;
}

static void *bpf_obj_do_get(const struct filename *pathname,
			    enum bpf_type *type, int flags)
{
	struct inode *inode;
	struct path path;
	void *raw;
	int ret;

	ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
	if (ret)
		return ERR_PTR(ret);

	inode = d_backing_inode(path.dentry);
	ret = inode_permission(inode, ACC_MODE(flags));
	if (ret)
		goto out;

	ret = bpf_inode_type(inode, type);
	if (ret)
		goto out;

	raw = bpf_any_get(inode->i_private, *type);
	if (!IS_ERR(raw))
		touch_atime(&path);

	path_put(&path);
	return raw;
out:
	path_put(&path);
	return ERR_PTR(ret);
}

int bpf_obj_get_user(const char __user *pathname, int flags)
{
	enum bpf_type type = BPF_TYPE_UNSPEC;
	struct filename *pname;
	int ret = -ENOENT;
	int f_flags;
	void *raw;

	f_flags = bpf_get_file_flag(flags);
	if (f_flags < 0)
		return f_flags;

	pname = getname(pathname);
	if (IS_ERR(pname))
		return PTR_ERR(pname);

	raw = bpf_obj_do_get(pname, &type, f_flags);
	if (IS_ERR(raw)) {
		ret = PTR_ERR(raw);
		goto out;
	}

	if (type == BPF_TYPE_PROG)
		ret = bpf_prog_new_fd(raw);
	else if (type == BPF_TYPE_MAP)
		ret = bpf_map_new_fd(raw, f_flags);
	else
		goto out;

	if (ret < 0)
		bpf_any_put(raw, type);
out:
	putname(pname);
	return ret;
}

static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)
{
	struct bpf_prog *prog;
	int ret = inode_permission(inode, MAY_READ);
	if (ret)
		return ERR_PTR(ret);

	if (inode->i_op == &bpf_map_iops)
		return ERR_PTR(-EINVAL);
	if (inode->i_op != &bpf_prog_iops)
		return ERR_PTR(-EACCES);

	prog = inode->i_private;

	ret = security_bpf_prog(prog);
	if (ret < 0)
		return ERR_PTR(ret);

	if (!bpf_prog_get_ok(prog, &type, false))
		return ERR_PTR(-EINVAL);

	return bpf_prog_inc(prog);
}

struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)
{
	struct bpf_prog *prog;
	struct path path;
	int ret = kern_path(name, LOOKUP_FOLLOW, &path);
	if (ret)
		return ERR_PTR(ret);
	prog = __get_prog_inode(d_backing_inode(path.dentry), type);
	if (!IS_ERR(prog))
		touch_atime(&path);
	path_put(&path);
	return prog;
}
EXPORT_SYMBOL(bpf_prog_get_type_path);

/*
 * Display the mount options in /proc/mounts.
 */
static int bpf_show_options(struct seq_file *m, struct dentry *root)
{
	umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX;

	if (mode != S_IRWXUGO)
		seq_printf(m, ",mode=%o", mode);
	return 0;
}

static void bpf_destroy_inode_deferred(struct rcu_head *head)
{
	struct inode *inode = container_of(head, struct inode, i_rcu);
	enum bpf_type type;

	if (S_ISLNK(inode->i_mode))
		kfree(inode->i_link);
	if (!bpf_inode_type(inode, &type))
		bpf_any_put(inode->i_private, type);
	free_inode_nonrcu(inode);
}

static void bpf_destroy_inode(struct inode *inode)
{
	call_rcu(&inode->i_rcu, bpf_destroy_inode_deferred);
}

static const struct super_operations bpf_super_ops = {
	.statfs		= simple_statfs,
	.drop_inode	= generic_delete_inode,
	.show_options	= bpf_show_options,
	.destroy_inode	= bpf_destroy_inode,
};

enum {
	OPT_MODE,
	OPT_ERR,
};

static const match_table_t bpf_mount_tokens = {
	{ OPT_MODE, "mode=%o" },
	{ OPT_ERR, NULL },
};

struct bpf_mount_opts {
	umode_t mode;
};

static int bpf_parse_options(char *data, struct bpf_mount_opts *opts)
{
	substring_t args[MAX_OPT_ARGS];
	int option, token;
	char *ptr;

	opts->mode = S_IRWXUGO;

	while ((ptr = strsep(&data, ",")) != NULL) {
		if (!*ptr)
			continue;

		token = match_token(ptr, bpf_mount_tokens, args);
		switch (token) {
		case OPT_MODE:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->mode = option & S_IALLUGO;
			break;
		/* We might like to report bad mount options here, but
		 * traditionally we've ignored all mount options, so we'd
		 * better continue to ignore non-existing options for bpf.
		 */
		}
	}

	return 0;
}

static int bpf_fill_super(struct super_block *sb, void *data, int silent)
{
	static const struct tree_descr bpf_rfiles[] = { { "" } };
	struct bpf_mount_opts opts;
	struct inode *inode;
	int ret;

	ret = bpf_parse_options(data, &opts);
	if (ret)
		return ret;

	ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
	if (ret)
		return ret;

	sb->s_op = &bpf_super_ops;

	inode = sb->s_root->d_inode;
	inode->i_op = &bpf_dir_iops;
	inode->i_mode &= ~S_IALLUGO;
	inode->i_mode |= S_ISVTX | opts.mode;

	return 0;
}

static struct dentry *bpf_mount(struct file_system_type *type, int flags,
				const char *dev_name, void *data)
{
	return mount_nodev(type, flags, data, bpf_fill_super);
}

static struct file_system_type bpf_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "bpf",
	.mount		= bpf_mount,
	.kill_sb	= kill_litter_super,
};

static int __init bpf_init(void)
{
	int ret;

	ret = sysfs_create_mount_point(fs_kobj, "bpf");
	if (ret)
		return ret;

	ret = register_filesystem(&bpf_fs_type);
	if (ret)
		sysfs_remove_mount_point(fs_kobj, "bpf");

	return ret;
}
fs_initcall(bpf_init);