1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Minimal file system backend for holding eBPF maps and programs,
  4 * used by bpf(2) object pinning.
  5 *
  6 * Authors:
  7 *
  8 *	Daniel Borkmann <daniel@iogearbox.net>
  9 */
 10
 11#include <linux/init.h>
 12#include <linux/magic.h>
 13#include <linux/major.h>
 14#include <linux/mount.h>
 15#include <linux/namei.h>
 16#include <linux/fs.h>
 17#include <linux/fs_context.h>
 18#include <linux/fs_parser.h>
 19#include <linux/kdev_t.h>
 20#include <linux/filter.h>
 21#include <linux/bpf.h>
 22#include <linux/bpf_trace.h>
 23
 24enum bpf_type {
 25	BPF_TYPE_UNSPEC	= 0,
 26	BPF_TYPE_PROG,
 27	BPF_TYPE_MAP,
 28};
 29
 30static void *bpf_any_get(void *raw, enum bpf_type type)
 31{
 32	switch (type) {
 33	case BPF_TYPE_PROG:
 34		raw = bpf_prog_inc(raw);
 35		break;
 36	case BPF_TYPE_MAP:
 37		raw = bpf_map_inc(raw, true);
 38		break;
 39	default:
 40		WARN_ON_ONCE(1);
 41		break;
 42	}
 43
 44	return raw;
 45}
 46
 47static void bpf_any_put(void *raw, enum bpf_type type)
 48{
 49	switch (type) {
 50	case BPF_TYPE_PROG:
 51		bpf_prog_put(raw);
 52		break;
 53	case BPF_TYPE_MAP:
 54		bpf_map_put_with_uref(raw);
 55		break;
 56	default:
 57		WARN_ON_ONCE(1);
 58		break;
 59	}
 60}
 61
 62static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
 63{
 64	void *raw;
 65
 66	*type = BPF_TYPE_MAP;
 67	raw = bpf_map_get_with_uref(ufd);
 68	if (IS_ERR(raw)) {
 69		*type = BPF_TYPE_PROG;
 70		raw = bpf_prog_get(ufd);
 71	}
 72
 73	return raw;
 74}
 75
 76static const struct inode_operations bpf_dir_iops;
 77
 78static const struct inode_operations bpf_prog_iops = { };
 79static const struct inode_operations bpf_map_iops  = { };
 80
 81static struct inode *bpf_get_inode(struct super_block *sb,
 82				   const struct inode *dir,
 83				   umode_t mode)
 84{
 85	struct inode *inode;
 86
 87	switch (mode & S_IFMT) {
 88	case S_IFDIR:
 89	case S_IFREG:
 90	case S_IFLNK:
 91		break;
 92	default:
 93		return ERR_PTR(-EINVAL);
 94	}
 95
 96	inode = new_inode(sb);
 97	if (!inode)
 98		return ERR_PTR(-ENOSPC);
 99
100	inode->i_ino = get_next_ino();
101	inode->i_atime = current_time(inode);
102	inode->i_mtime = inode->i_atime;
103	inode->i_ctime = inode->i_atime;
104
105	inode_init_owner(inode, dir, mode);
106
107	return inode;
108}
109
110static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
111{
112	*type = BPF_TYPE_UNSPEC;
113	if (inode->i_op == &bpf_prog_iops)
114		*type = BPF_TYPE_PROG;
115	else if (inode->i_op == &bpf_map_iops)
116		*type = BPF_TYPE_MAP;
117	else
118		return -EACCES;
119
120	return 0;
121}
122
123static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode,
124				struct inode *dir)
125{
126	d_instantiate(dentry, inode);
127	dget(dentry);
128
129	dir->i_mtime = current_time(dir);
130	dir->i_ctime = dir->i_mtime;
131}
132
133static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
134{
135	struct inode *inode;
136
137	inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
138	if (IS_ERR(inode))
139		return PTR_ERR(inode);
140
141	inode->i_op = &bpf_dir_iops;
142	inode->i_fop = &simple_dir_operations;
143
144	inc_nlink(inode);
145	inc_nlink(dir);
146
147	bpf_dentry_finalize(dentry, inode, dir);
148	return 0;
149}
150
151struct map_iter {
152	void *key;
153	bool done;
154};
155
156static struct map_iter *map_iter(struct seq_file *m)
157{
158	return m->private;
159}
160
161static struct bpf_map *seq_file_to_map(struct seq_file *m)
162{
163	return file_inode(m->file)->i_private;
164}
165
166static void map_iter_free(struct map_iter *iter)
167{
168	if (iter) {
169		kfree(iter->key);
170		kfree(iter);
171	}
172}
173
174static struct map_iter *map_iter_alloc(struct bpf_map *map)
175{
176	struct map_iter *iter;
177
178	iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN);
179	if (!iter)
180		goto error;
181
182	iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN);
183	if (!iter->key)
184		goto error;
185
186	return iter;
187
188error:
189	map_iter_free(iter);
190	return NULL;
191}
192
193static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)
194{
195	struct bpf_map *map = seq_file_to_map(m);
196	void *key = map_iter(m)->key;
197	void *prev_key;
198
199	if (map_iter(m)->done)
200		return NULL;
201
202	if (unlikely(v == SEQ_START_TOKEN))
203		prev_key = NULL;
204	else
205		prev_key = key;
206
207	if (map->ops->map_get_next_key(map, prev_key, key)) {
208		map_iter(m)->done = true;
209		return NULL;
210	}
211
212	++(*pos);
213	return key;
214}
215
216static void *map_seq_start(struct seq_file *m, loff_t *pos)
217{
218	if (map_iter(m)->done)
219		return NULL;
220
221	return *pos ? map_iter(m)->key : SEQ_START_TOKEN;
222}
223
224static void map_seq_stop(struct seq_file *m, void *v)
225{
226}
227
228static int map_seq_show(struct seq_file *m, void *v)
229{
230	struct bpf_map *map = seq_file_to_map(m);
231	void *key = map_iter(m)->key;
232
233	if (unlikely(v == SEQ_START_TOKEN)) {
234		seq_puts(m, "# WARNING!! The output is for debug purpose only\n");
235		seq_puts(m, "# WARNING!! The output format will change\n");
236	} else {
237		map->ops->map_seq_show_elem(map, key, m);
238	}
239
240	return 0;
241}
242
243static const struct seq_operations bpffs_map_seq_ops = {
244	.start	= map_seq_start,
245	.next	= map_seq_next,
246	.show	= map_seq_show,
247	.stop	= map_seq_stop,
248};
249
250static int bpffs_map_open(struct inode *inode, struct file *file)
251{
252	struct bpf_map *map = inode->i_private;
253	struct map_iter *iter;
254	struct seq_file *m;
255	int err;
256
257	iter = map_iter_alloc(map);
258	if (!iter)
259		return -ENOMEM;
260
261	err = seq_open(file, &bpffs_map_seq_ops);
262	if (err) {
263		map_iter_free(iter);
264		return err;
265	}
266
267	m = file->private_data;
268	m->private = iter;
269
270	return 0;
271}
272
273static int bpffs_map_release(struct inode *inode, struct file *file)
274{
275	struct seq_file *m = file->private_data;
276
277	map_iter_free(map_iter(m));
278
279	return seq_release(inode, file);
280}
281
282/* bpffs_map_fops should only implement the basic
283 * read operation for a BPF map.  The purpose is to
284 * provide a simple user intuitive way to do
285 * "cat bpffs/pathto/a-pinned-map".
286 *
287 * Other operations (e.g. write, lookup...) should be realized by
288 * the userspace tools (e.g. bpftool) through the
289 * BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update
290 * interface.
291 */
292static const struct file_operations bpffs_map_fops = {
293	.open		= bpffs_map_open,
294	.read		= seq_read,
295	.release	= bpffs_map_release,
296};
297
298static int bpffs_obj_open(struct inode *inode, struct file *file)
299{
300	return -EIO;
301}
302
303static const struct file_operations bpffs_obj_fops = {
304	.open		= bpffs_obj_open,
305};
306
307static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
308			 const struct inode_operations *iops,
309			 const struct file_operations *fops)
310{
311	struct inode *dir = dentry->d_parent->d_inode;
312	struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode);
313	if (IS_ERR(inode))
314		return PTR_ERR(inode);
315
316	inode->i_op = iops;
317	inode->i_fop = fops;
318	inode->i_private = raw;
319
320	bpf_dentry_finalize(dentry, inode, dir);
321	return 0;
322}
323
324static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)
325{
326	return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,
327			     &bpffs_obj_fops);
328}
329
330static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
331{
332	struct bpf_map *map = arg;
333
334	return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,
335			     bpf_map_support_seq_show(map) ?
336			     &bpffs_map_fops : &bpffs_obj_fops);
337}
338
339static struct dentry *
340bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
341{
342	/* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future
343	 * extensions.
344	 */
345	if (strchr(dentry->d_name.name, '.'))
346		return ERR_PTR(-EPERM);
347
348	return simple_lookup(dir, dentry, flags);
349}
350
351static int bpf_symlink(struct inode *dir, struct dentry *dentry,
352		       const char *target)
353{
354	char *link = kstrdup(target, GFP_USER | __GFP_NOWARN);
355	struct inode *inode;
356
357	if (!link)
358		return -ENOMEM;
359
360	inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK);
361	if (IS_ERR(inode)) {
362		kfree(link);
363		return PTR_ERR(inode);
364	}
365
366	inode->i_op = &simple_symlink_inode_operations;
367	inode->i_link = link;
368
369	bpf_dentry_finalize(dentry, inode, dir);
370	return 0;
371}
372
373static const struct inode_operations bpf_dir_iops = {
374	.lookup		= bpf_lookup,
375	.mkdir		= bpf_mkdir,
376	.symlink	= bpf_symlink,
377	.rmdir		= simple_rmdir,
378	.rename		= simple_rename,
379	.link		= simple_link,
380	.unlink		= simple_unlink,
381};
382
383static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
384			  enum bpf_type type)
385{
386	struct dentry *dentry;
387	struct inode *dir;
388	struct path path;
389	umode_t mode;
390	int ret;
391
392	dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
393	if (IS_ERR(dentry))
394		return PTR_ERR(dentry);
395
396	mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
397
398	ret = security_path_mknod(&path, dentry, mode, 0);
399	if (ret)
400		goto out;
401
402	dir = d_inode(path.dentry);
403	if (dir->i_op != &bpf_dir_iops) {
404		ret = -EPERM;
405		goto out;
406	}
407
408	switch (type) {
409	case BPF_TYPE_PROG:
410		ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw);
411		break;
412	case BPF_TYPE_MAP:
413		ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);
414		break;
415	default:
416		ret = -EPERM;
417	}
418out:
419	done_path_create(&path, dentry);
420	return ret;
421}
422
423int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
424{
425	struct filename *pname;
426	enum bpf_type type;
427	void *raw;
428	int ret;
429
430	pname = getname(pathname);
431	if (IS_ERR(pname))
432		return PTR_ERR(pname);
433
434	raw = bpf_fd_probe_obj(ufd, &type);
435	if (IS_ERR(raw)) {
436		ret = PTR_ERR(raw);
437		goto out;
438	}
439
440	ret = bpf_obj_do_pin(pname, raw, type);
441	if (ret != 0)
442		bpf_any_put(raw, type);
443out:
444	putname(pname);
445	return ret;
446}
447
448static void *bpf_obj_do_get(const struct filename *pathname,
449			    enum bpf_type *type, int flags)
450{
451	struct inode *inode;
452	struct path path;
453	void *raw;
454	int ret;
455
456	ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
457	if (ret)
458		return ERR_PTR(ret);
459
460	inode = d_backing_inode(path.dentry);
461	ret = inode_permission(inode, ACC_MODE(flags));
462	if (ret)
463		goto out;
464
465	ret = bpf_inode_type(inode, type);
466	if (ret)
467		goto out;
468
469	raw = bpf_any_get(inode->i_private, *type);
470	if (!IS_ERR(raw))
471		touch_atime(&path);
472
473	path_put(&path);
474	return raw;
475out:
476	path_put(&path);
477	return ERR_PTR(ret);
478}
479
480int bpf_obj_get_user(const char __user *pathname, int flags)
481{
482	enum bpf_type type = BPF_TYPE_UNSPEC;
483	struct filename *pname;
484	int ret = -ENOENT;
485	int f_flags;
486	void *raw;
487
488	f_flags = bpf_get_file_flag(flags);
489	if (f_flags < 0)
490		return f_flags;
491
492	pname = getname(pathname);
493	if (IS_ERR(pname))
494		return PTR_ERR(pname);
495
496	raw = bpf_obj_do_get(pname, &type, f_flags);
497	if (IS_ERR(raw)) {
498		ret = PTR_ERR(raw);
499		goto out;
500	}
501
502	if (type == BPF_TYPE_PROG)
503		ret = bpf_prog_new_fd(raw);
504	else if (type == BPF_TYPE_MAP)
505		ret = bpf_map_new_fd(raw, f_flags);
506	else
507		goto out;
508
509	if (ret < 0)
510		bpf_any_put(raw, type);
511out:
512	putname(pname);
513	return ret;
514}
515
516static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)
517{
518	struct bpf_prog *prog;
519	int ret = inode_permission(inode, MAY_READ);
520	if (ret)
521		return ERR_PTR(ret);
522
523	if (inode->i_op == &bpf_map_iops)
524		return ERR_PTR(-EINVAL);
525	if (inode->i_op != &bpf_prog_iops)
526		return ERR_PTR(-EACCES);
527
528	prog = inode->i_private;
529
530	ret = security_bpf_prog(prog);
531	if (ret < 0)
532		return ERR_PTR(ret);
533
534	if (!bpf_prog_get_ok(prog, &type, false))
535		return ERR_PTR(-EINVAL);
536
537	return bpf_prog_inc(prog);
538}
539
540struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)
541{
542	struct bpf_prog *prog;
543	struct path path;
544	int ret = kern_path(name, LOOKUP_FOLLOW, &path);
545	if (ret)
546		return ERR_PTR(ret);
547	prog = __get_prog_inode(d_backing_inode(path.dentry), type);
548	if (!IS_ERR(prog))
549		touch_atime(&path);
550	path_put(&path);
551	return prog;
552}
553EXPORT_SYMBOL(bpf_prog_get_type_path);
554
555/*
556 * Display the mount options in /proc/mounts.
557 */
558static int bpf_show_options(struct seq_file *m, struct dentry *root)
559{
560	umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX;
561
562	if (mode != S_IRWXUGO)
563		seq_printf(m, ",mode=%o", mode);
564	return 0;
565}
566
567static void bpf_free_inode(struct inode *inode)
568{
569	enum bpf_type type;
570
571	if (S_ISLNK(inode->i_mode))
572		kfree(inode->i_link);
573	if (!bpf_inode_type(inode, &type))
574		bpf_any_put(inode->i_private, type);
575	free_inode_nonrcu(inode);
576}
577
578static const struct super_operations bpf_super_ops = {
579	.statfs		= simple_statfs,
580	.drop_inode	= generic_delete_inode,
581	.show_options	= bpf_show_options,
582	.free_inode	= bpf_free_inode,
583};
584
585enum {
586	OPT_MODE,
587};
588
589static const struct fs_parameter_spec bpf_param_specs[] = {
590	fsparam_u32oct	("mode",			OPT_MODE),
591	{}
592};
593
594static const struct fs_parameter_description bpf_fs_parameters = {
595	.name		= "bpf",
596	.specs		= bpf_param_specs,
597};
598
599struct bpf_mount_opts {
600	umode_t mode;
601};
602
603static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param)
604{
605	struct bpf_mount_opts *opts = fc->fs_private;
606	struct fs_parse_result result;
607	int opt;
608
609	opt = fs_parse(fc, &bpf_fs_parameters, param, &result);
610	if (opt < 0)
611		/* We might like to report bad mount options here, but
612		 * traditionally we've ignored all mount options, so we'd
613		 * better continue to ignore non-existing options for bpf.
614		 */
615		return opt == -ENOPARAM ? 0 : opt;
616
617	switch (opt) {
618	case OPT_MODE:
619		opts->mode = result.uint_32 & S_IALLUGO;
620		break;
621	}
622
623	return 0;
624}
625
626static int bpf_fill_super(struct super_block *sb, struct fs_context *fc)
627{
628	static const struct tree_descr bpf_rfiles[] = { { "" } };
629	struct bpf_mount_opts *opts = fc->fs_private;
630	struct inode *inode;
631	int ret;
632
633	ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
634	if (ret)
635		return ret;
636
637	sb->s_op = &bpf_super_ops;
638
639	inode = sb->s_root->d_inode;
640	inode->i_op = &bpf_dir_iops;
641	inode->i_mode &= ~S_IALLUGO;
642	inode->i_mode |= S_ISVTX | opts->mode;
643
644	return 0;
645}
646
647static int bpf_get_tree(struct fs_context *fc)
648{
649	return get_tree_nodev(fc, bpf_fill_super);
650}
651
652static void bpf_free_fc(struct fs_context *fc)
653{
654	kfree(fc->fs_private);
655}
656
657static const struct fs_context_operations bpf_context_ops = {
658	.free		= bpf_free_fc,
659	.parse_param	= bpf_parse_param,
660	.get_tree	= bpf_get_tree,
661};
662
663/*
664 * Set up the filesystem mount context.
665 */
666static int bpf_init_fs_context(struct fs_context *fc)
667{
668	struct bpf_mount_opts *opts;
669
670	opts = kzalloc(sizeof(struct bpf_mount_opts), GFP_KERNEL);
671	if (!opts)
672		return -ENOMEM;
673
674	opts->mode = S_IRWXUGO;
675
676	fc->fs_private = opts;
677	fc->ops = &bpf_context_ops;
678	return 0;
679}
680
681static struct file_system_type bpf_fs_type = {
682	.owner		= THIS_MODULE,
683	.name		= "bpf",
684	.init_fs_context = bpf_init_fs_context,
685	.parameters	= &bpf_fs_parameters,
686	.kill_sb	= kill_litter_super,
687};
688
689static int __init bpf_init(void)
690{
691	int ret;
692
693	ret = sysfs_create_mount_point(fs_kobj, "bpf");
694	if (ret)
695		return ret;
696
697	ret = register_filesystem(&bpf_fs_type);
698	if (ret)
699		sysfs_remove_mount_point(fs_kobj, "bpf");
700
701	return ret;
702}
703fs_initcall(bpf_init);