binderfs.c

  1// SPDX-License-Identifier: GPL-2.0
  2
  3#include <linux/compiler_types.h>
  4#include <linux/errno.h>
  5#include <linux/fs.h>
  6#include <linux/fsnotify.h>
  7#include <linux/gfp.h>
  8#include <linux/idr.h>
  9#include <linux/init.h>
 10#include <linux/ipc_namespace.h>
 11#include <linux/kdev_t.h>
 12#include <linux/kernel.h>
 13#include <linux/list.h>
 14#include <linux/namei.h>
 15#include <linux/magic.h>
 16#include <linux/major.h>
 17#include <linux/miscdevice.h>
 18#include <linux/module.h>
 19#include <linux/mutex.h>
 20#include <linux/mount.h>
 21#include <linux/fs_parser.h>
 22#include <linux/sched.h>
 23#include <linux/seq_file.h>
 24#include <linux/slab.h>
 25#include <linux/spinlock_types.h>
 26#include <linux/stddef.h>
 27#include <linux/string.h>
 28#include <linux/types.h>
 29#include <linux/uaccess.h>
 30#include <linux/user_namespace.h>
 31#include <linux/xarray.h>
 32#include <uapi/linux/android/binder.h>
 33#include <uapi/linux/android/binderfs.h>
 34
 35#include "binder_internal.h"
 36
 37#define FIRST_INODE 1
 38#define SECOND_INODE 2
 39#define INODE_OFFSET 3
 40#define BINDERFS_MAX_MINOR (1U << MINORBITS)
 41/* Ensure that the initial ipc namespace always has devices available. */
 42#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4)
 43
 44static dev_t binderfs_dev;
 45static DEFINE_MUTEX(binderfs_minors_mutex);
 46static DEFINE_IDA(binderfs_minors);
 47
 48enum binderfs_param {
 49	Opt_max,
 50	Opt_stats_mode,
 51};
 52
 53enum binderfs_stats_mode {
 54	binderfs_stats_mode_unset,
 55	binderfs_stats_mode_global,
 56};
 57
 58struct binder_features {
 59	bool oneway_spam_detection;
 60	bool extended_error;
 61	bool freeze_notification;
 62	bool transaction_report;
 63};
 64
 65static const struct constant_table binderfs_param_stats[] = {
 66	{ "global", binderfs_stats_mode_global },
 67	{}
 68};
 69
 70static const struct fs_parameter_spec binderfs_fs_parameters[] = {
 71	fsparam_u32("max",	Opt_max),
 72	fsparam_enum("stats",	Opt_stats_mode, binderfs_param_stats),
 73	{}
 74};
 75
 76static struct binder_features binder_features = {
 77	.oneway_spam_detection = true,
 78	.extended_error = true,
 79	.freeze_notification = true,
 80	.transaction_report = true,
 81};
 82
 83static inline struct binderfs_info *BINDERFS_SB(const struct super_block *sb)
 84{
 85	return sb->s_fs_info;
 86}
 87
 88bool is_binderfs_device(const struct inode *inode)
 89{
 90	if (inode->i_sb->s_magic == BINDERFS_SUPER_MAGIC)
 91		return true;
 92
 93	return false;
 94}
 95
 96/**
 97 * binderfs_binder_device_create - allocate inode from super block of a
 98 *                                 binderfs mount
 99 * @ref_inode: inode from which the super block will be taken
100 * @userp:     buffer to copy information about new device for userspace to
101 * @req:       struct binderfs_device as copied from userspace
102 *
103 * This function allocates a new binder_device and reserves a new minor
104 * number for it.
105 * Minor numbers are limited and tracked globally in binderfs_minors. The
106 * function will stash a struct binder_device for the specific binder
107 * device in i_private of the inode.
108 * It will go on to allocate a new inode from the super block of the
109 * filesystem mount, stash a struct binder_device in its i_private field
110 * and attach a dentry to that inode.
111 *
112 * Return: 0 on success, negative errno on failure
113 */
114static int binderfs_binder_device_create(struct inode *ref_inode,
115					 struct binderfs_device __user *userp,
116					 struct binderfs_device *req)
117{
118	int minor, ret;
119	struct dentry *dentry, *root;
120	struct binder_device *device;
121	char *name = NULL;
122	struct inode *inode = NULL;
123	struct super_block *sb = ref_inode->i_sb;
124	struct binderfs_info *info = sb->s_fs_info;
125#if defined(CONFIG_IPC_NS)
126	bool use_reserve = (info->ipc_ns == &init_ipc_ns);
127#else
128	bool use_reserve = true;
129#endif
130
131	/* Reserve new minor number for the new device. */
132	mutex_lock(&binderfs_minors_mutex);
133	if (++info->device_count <= info->mount_opts.max)
134		minor = ida_alloc_max(&binderfs_minors,
135				      use_reserve ? BINDERFS_MAX_MINOR - 1 :
136						    BINDERFS_MAX_MINOR_CAPPED - 1,
137				      GFP_KERNEL);
138	else
139		minor = -ENOSPC;
140	if (minor < 0) {
141		--info->device_count;
142		mutex_unlock(&binderfs_minors_mutex);
143		return minor;
144	}
145	mutex_unlock(&binderfs_minors_mutex);
146
147	ret = -ENOMEM;
148	device = kzalloc(sizeof(*device), GFP_KERNEL);
149	if (!device)
150		goto err;
151
152	inode = new_inode(sb);
153	if (!inode)
154		goto err;
155
156	inode->i_ino = minor + INODE_OFFSET;
157	simple_inode_init_ts(inode);
158	init_special_inode(inode, S_IFCHR | 0600,
159			   MKDEV(MAJOR(binderfs_dev), minor));
160	inode->i_fop = &binder_fops;
161	inode->i_uid = info->root_uid;
162	inode->i_gid = info->root_gid;
163
164	req->name[BINDERFS_MAX_NAME] = '\0'; /* NUL-terminate */
165	name = kstrdup(req->name, GFP_KERNEL);
166	if (!name)
167		goto err;
168
169	refcount_set(&device->ref, 1);
170	device->binderfs_inode = inode;
171	device->context.binder_context_mgr_uid = INVALID_UID;
172	device->context.name = name;
173	device->miscdev.name = name;
174	device->miscdev.minor = minor;
175	mutex_init(&device->context.context_mgr_node_lock);
176
177	req->major = MAJOR(binderfs_dev);
178	req->minor = minor;
179
180	if (userp && copy_to_user(userp, req, sizeof(*req))) {
181		ret = -EFAULT;
182		goto err;
183	}
184
185	root = sb->s_root;
186	dentry = simple_start_creating(root, name);
187	if (IS_ERR(dentry)) {
188		ret = PTR_ERR(dentry);
189		goto err;
190	}
191	inode->i_private = device;
192	d_make_persistent(dentry, inode);
193	fsnotify_create(root->d_inode, dentry);
194	simple_done_creating(dentry);
195
196	binder_add_device(device);
197
198	return 0;
199
200err:
201	kfree(name);
202	kfree(device);
203	mutex_lock(&binderfs_minors_mutex);
204	--info->device_count;
205	ida_free(&binderfs_minors, minor);
206	mutex_unlock(&binderfs_minors_mutex);
207	iput(inode);
208
209	return ret;
210}
211
212/**
213 * binder_ctl_ioctl - handle binder device node allocation requests
214 * @file: The file pointer for the binder-control device node.
215 * @cmd: The ioctl command.
216 * @arg: The ioctl argument.
217 *
218 * The request handler for the binder-control device. All requests operate on
219 * the binderfs mount the binder-control device resides in:
220 * - BINDER_CTL_ADD
221 *   Allocate a new binder device.
222 *
223 * Return: %0 on success, negative errno on failure.
224 */
225static long binder_ctl_ioctl(struct file *file, unsigned int cmd,
226			     unsigned long arg)
227{
228	int ret = -EINVAL;
229	struct inode *inode = file_inode(file);
230	struct binderfs_device __user *device = (struct binderfs_device __user *)arg;
231	struct binderfs_device device_req;
232
233	switch (cmd) {
234	case BINDER_CTL_ADD:
235		ret = copy_from_user(&device_req, device, sizeof(device_req));
236		if (ret) {
237			ret = -EFAULT;
238			break;
239		}
240
241		ret = binderfs_binder_device_create(inode, device, &device_req);
242		break;
243	default:
244		break;
245	}
246
247	return ret;
248}
249
250static void binderfs_evict_inode(struct inode *inode)
251{
252	struct binder_device *device = inode->i_private;
253	struct binderfs_info *info = BINDERFS_SB(inode->i_sb);
254
255	clear_inode(inode);
256
257	if (!S_ISCHR(inode->i_mode) || !device)
258		return;
259
260	mutex_lock(&binderfs_minors_mutex);
261	--info->device_count;
262	ida_free(&binderfs_minors, device->miscdev.minor);
263	mutex_unlock(&binderfs_minors_mutex);
264
265	if (refcount_dec_and_test(&device->ref)) {
266		binder_remove_device(device);
267		kfree(device->context.name);
268		kfree(device);
269	}
270}
271
272static int binderfs_fs_context_parse_param(struct fs_context *fc,
273					   struct fs_parameter *param)
274{
275	int opt;
276	struct binderfs_mount_opts *ctx = fc->fs_private;
277	struct fs_parse_result result;
278
279	opt = fs_parse(fc, binderfs_fs_parameters, param, &result);
280	if (opt < 0)
281		return opt;
282
283	switch (opt) {
284	case Opt_max:
285		if (result.uint_32 > BINDERFS_MAX_MINOR)
286			return invalfc(fc, "Bad value for '%s'", param->key);
287
288		ctx->max = result.uint_32;
289		break;
290	case Opt_stats_mode:
291		if (!capable(CAP_SYS_ADMIN))
292			return -EPERM;
293
294		ctx->stats_mode = result.uint_32;
295		break;
296	default:
297		return invalfc(fc, "Unsupported parameter '%s'", param->key);
298	}
299
300	return 0;
301}
302
303static int binderfs_fs_context_reconfigure(struct fs_context *fc)
304{
305	struct binderfs_mount_opts *ctx = fc->fs_private;
306	struct binderfs_info *info = BINDERFS_SB(fc->root->d_sb);
307
308	if (info->mount_opts.stats_mode != ctx->stats_mode)
309		return invalfc(fc, "Binderfs stats mode cannot be changed during a remount");
310
311	info->mount_opts.stats_mode = ctx->stats_mode;
312	info->mount_opts.max = ctx->max;
313	return 0;
314}
315
316static int binderfs_show_options(struct seq_file *seq, struct dentry *root)
317{
318	struct binderfs_info *info = BINDERFS_SB(root->d_sb);
319
320	if (info->mount_opts.max <= BINDERFS_MAX_MINOR)
321		seq_printf(seq, ",max=%d", info->mount_opts.max);
322
323	switch (info->mount_opts.stats_mode) {
324	case binderfs_stats_mode_unset:
325		break;
326	case binderfs_stats_mode_global:
327		seq_printf(seq, ",stats=global");
328		break;
329	}
330
331	return 0;
332}
333
334static const struct super_operations binderfs_super_ops = {
335	.evict_inode    = binderfs_evict_inode,
336	.show_options	= binderfs_show_options,
337	.statfs         = simple_statfs,
338};
339
340static inline bool is_binderfs_control_device(const struct dentry *dentry)
341{
342	struct binderfs_info *info = dentry->d_sb->s_fs_info;
343
344	return info->control_dentry == dentry;
345}
346
347static int binderfs_rename(struct mnt_idmap *idmap,
348			   struct inode *old_dir, struct dentry *old_dentry,
349			   struct inode *new_dir, struct dentry *new_dentry,
350			   unsigned int flags)
351{
352	if (is_binderfs_control_device(old_dentry) ||
353	    is_binderfs_control_device(new_dentry))
354		return -EPERM;
355
356	return simple_rename(idmap, old_dir, old_dentry, new_dir,
357			     new_dentry, flags);
358}
359
360static int binderfs_unlink(struct inode *dir, struct dentry *dentry)
361{
362	if (is_binderfs_control_device(dentry))
363		return -EPERM;
364
365	return simple_unlink(dir, dentry);
366}
367
368static const struct file_operations binder_ctl_fops = {
369	.owner		= THIS_MODULE,
370	.open		= nonseekable_open,
371	.unlocked_ioctl	= binder_ctl_ioctl,
372	.compat_ioctl	= binder_ctl_ioctl,
373	.llseek		= noop_llseek,
374};
375
376/**
377 * binderfs_binder_ctl_create - create a new binder-control device
378 * @sb: super block of the binderfs mount
379 *
380 * This function creates a new binder-control device node in the binderfs mount
381 * referred to by @sb.
382 *
383 * Return: 0 on success, negative errno on failure
384 */
385static int binderfs_binder_ctl_create(struct super_block *sb)
386{
387	int minor, ret;
388	struct dentry *dentry;
389	struct binder_device *device;
390	struct inode *inode = NULL;
391	struct dentry *root = sb->s_root;
392	struct binderfs_info *info = sb->s_fs_info;
393#if defined(CONFIG_IPC_NS)
394	bool use_reserve = (info->ipc_ns == &init_ipc_ns);
395#else
396	bool use_reserve = true;
397#endif
398
399	device = kzalloc(sizeof(*device), GFP_KERNEL);
400	if (!device)
401		return -ENOMEM;
402
403	ret = -ENOMEM;
404	inode = new_inode(sb);
405	if (!inode)
406		goto out;
407
408	/* Reserve a new minor number for the new device. */
409	mutex_lock(&binderfs_minors_mutex);
410	minor = ida_alloc_max(&binderfs_minors,
411			      use_reserve ? BINDERFS_MAX_MINOR - 1 :
412					    BINDERFS_MAX_MINOR_CAPPED - 1,
413			      GFP_KERNEL);
414	mutex_unlock(&binderfs_minors_mutex);
415	if (minor < 0) {
416		ret = minor;
417		goto out;
418	}
419
420	inode->i_ino = SECOND_INODE;
421	simple_inode_init_ts(inode);
422	init_special_inode(inode, S_IFCHR | 0600,
423			   MKDEV(MAJOR(binderfs_dev), minor));
424	inode->i_fop = &binder_ctl_fops;
425	inode->i_uid = info->root_uid;
426	inode->i_gid = info->root_gid;
427
428	refcount_set(&device->ref, 1);
429	device->binderfs_inode = inode;
430	device->miscdev.minor = minor;
431
432	dentry = d_alloc_name(root, "binder-control");
433	if (!dentry)
434		goto out;
435
436	inode->i_private = device;
437	info->control_dentry = dentry;
438	d_make_persistent(dentry, inode);
439	dput(dentry);
440
441	return 0;
442
443out:
444	kfree(device);
445	iput(inode);
446
447	return ret;
448}
449
450static const struct inode_operations binderfs_dir_inode_operations = {
451	.lookup = simple_lookup,
452	.rename = binderfs_rename,
453	.unlink = binderfs_unlink,
454};
455
456static struct inode *binderfs_make_inode(struct super_block *sb, int mode)
457{
458	struct inode *ret;
459
460	ret = new_inode(sb);
461	if (ret) {
462		ret->i_ino = iunique(sb, BINDERFS_MAX_MINOR + INODE_OFFSET);
463		ret->i_mode = mode;
464		simple_inode_init_ts(ret);
465	}
466	return ret;
467}
468
469struct dentry *binderfs_create_file(struct dentry *parent, const char *name,
470				    const struct file_operations *fops,
471				    void *data)
472{
473	struct dentry *dentry;
474	struct inode *new_inode, *parent_inode;
475	struct super_block *sb;
476
477	parent_inode = d_inode(parent);
478
479	dentry = simple_start_creating(parent, name);
480	if (IS_ERR(dentry))
481		return dentry;
482
483	sb = parent_inode->i_sb;
484	new_inode = binderfs_make_inode(sb, S_IFREG | 0444);
485	if (!new_inode) {
486		simple_done_creating(dentry);
487		return ERR_PTR(-ENOMEM);
488	}
489
490	new_inode->i_fop = fops;
491	new_inode->i_private = data;
492	d_make_persistent(dentry, new_inode);
493	fsnotify_create(parent_inode, dentry);
494	simple_done_creating(dentry);
495	return dentry; // borrowed
496}
497
498static struct dentry *binderfs_create_dir(struct dentry *parent,
499					  const char *name)
500{
501	struct dentry *dentry;
502	struct inode *new_inode, *parent_inode;
503	struct super_block *sb;
504
505	parent_inode = d_inode(parent);
506
507	dentry = simple_start_creating(parent, name);
508	if (IS_ERR(dentry))
509		return dentry;
510
511	sb = parent_inode->i_sb;
512	new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);
513	if (!new_inode) {
514		simple_done_creating(dentry);
515		return ERR_PTR(-ENOMEM);
516	}
517
518	new_inode->i_fop = &simple_dir_operations;
519	new_inode->i_op = &simple_dir_inode_operations;
520
521	set_nlink(new_inode, 2);
522	d_make_persistent(dentry, new_inode);
523	inc_nlink(parent_inode);
524	fsnotify_mkdir(parent_inode, dentry);
525	simple_done_creating(dentry);
526	return dentry;
527}
528
529static int binder_features_show(struct seq_file *m, void *unused)
530{
531	bool *feature = m->private;
532
533	seq_printf(m, "%d\n", *feature);
534
535	return 0;
536}
537DEFINE_SHOW_ATTRIBUTE(binder_features);
538
539static int init_binder_features(struct super_block *sb)
540{
541	struct dentry *dentry, *dir;
542
543	dir = binderfs_create_dir(sb->s_root, "features");
544	if (IS_ERR(dir))
545		return PTR_ERR(dir);
546
547	dentry = binderfs_create_file(dir, "oneway_spam_detection",
548				      &binder_features_fops,
549				      &binder_features.oneway_spam_detection);
550	if (IS_ERR(dentry))
551		return PTR_ERR(dentry);
552
553	dentry = binderfs_create_file(dir, "extended_error",
554				      &binder_features_fops,
555				      &binder_features.extended_error);
556	if (IS_ERR(dentry))
557		return PTR_ERR(dentry);
558
559	dentry = binderfs_create_file(dir, "freeze_notification",
560				      &binder_features_fops,
561				      &binder_features.freeze_notification);
562	if (IS_ERR(dentry))
563		return PTR_ERR(dentry);
564
565	dentry = binderfs_create_file(dir, "transaction_report",
566				      &binder_features_fops,
567				      &binder_features.transaction_report);
568	if (IS_ERR(dentry))
569		return PTR_ERR(dentry);
570
571	return 0;
572}
573
574static int init_binder_logs(struct super_block *sb)
575{
576	struct dentry *binder_logs_root_dir, *dentry, *proc_log_dir;
577	const struct binder_debugfs_entry *db_entry;
578	struct binderfs_info *info;
579	int ret = 0;
580
581	binder_logs_root_dir = binderfs_create_dir(sb->s_root,
582						   "binder_logs");
583	if (IS_ERR(binder_logs_root_dir)) {
584		ret = PTR_ERR(binder_logs_root_dir);
585		goto out;
586	}
587
588	binder_for_each_debugfs_entry(db_entry) {
589		dentry = binderfs_create_file(binder_logs_root_dir,
590					      db_entry->name,
591					      db_entry->fops,
592					      db_entry->data);
593		if (IS_ERR(dentry)) {
594			ret = PTR_ERR(dentry);
595			goto out;
596		}
597	}
598
599	proc_log_dir = binderfs_create_dir(binder_logs_root_dir, "proc");
600	if (IS_ERR(proc_log_dir)) {
601		ret = PTR_ERR(proc_log_dir);
602		goto out;
603	}
604	info = sb->s_fs_info;
605	info->proc_log_dir = proc_log_dir;
606
607out:
608	return ret;
609}
610
611static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc)
612{
613	int ret;
614	struct binderfs_info *info;
615	struct binderfs_mount_opts *ctx = fc->fs_private;
616	struct inode *inode = NULL;
617	struct binderfs_device device_info = {};
618	const char *name;
619	size_t len;
620
621	sb->s_blocksize = PAGE_SIZE;
622	sb->s_blocksize_bits = PAGE_SHIFT;
623
624	/*
625	 * The binderfs filesystem can be mounted by userns root in a
626	 * non-initial userns. By default such mounts have the SB_I_NODEV flag
627	 * set in s_iflags to prevent security issues where userns root can
628	 * just create random device nodes via mknod() since it owns the
629	 * filesystem mount. But binderfs does not allow to create any files
630	 * including devices nodes. The only way to create binder devices nodes
631	 * is through the binder-control device which userns root is explicitly
632	 * allowed to do. So removing the SB_I_NODEV flag from s_iflags is both
633	 * necessary and safe.
634	 */
635	sb->s_iflags &= ~SB_I_NODEV;
636	sb->s_iflags |= SB_I_NOEXEC;
637	sb->s_magic = BINDERFS_SUPER_MAGIC;
638	sb->s_op = &binderfs_super_ops;
639	sb->s_time_gran = 1;
640
641	sb->s_fs_info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);
642	if (!sb->s_fs_info)
643		return -ENOMEM;
644	info = sb->s_fs_info;
645
646	info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
647
648	info->root_gid = make_kgid(sb->s_user_ns, 0);
649	if (!gid_valid(info->root_gid))
650		info->root_gid = GLOBAL_ROOT_GID;
651	info->root_uid = make_kuid(sb->s_user_ns, 0);
652	if (!uid_valid(info->root_uid))
653		info->root_uid = GLOBAL_ROOT_UID;
654	info->mount_opts.max = ctx->max;
655	info->mount_opts.stats_mode = ctx->stats_mode;
656
657	inode = new_inode(sb);
658	if (!inode)
659		return -ENOMEM;
660
661	inode->i_ino = FIRST_INODE;
662	inode->i_fop = &simple_dir_operations;
663	inode->i_mode = S_IFDIR | 0755;
664	simple_inode_init_ts(inode);
665	inode->i_op = &binderfs_dir_inode_operations;
666	set_nlink(inode, 2);
667
668	sb->s_root = d_make_root(inode);
669	if (!sb->s_root)
670		return -ENOMEM;
671
672	ret = binderfs_binder_ctl_create(sb);
673	if (ret)
674		return ret;
675
676	name = binder_devices_param;
677	for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
678		strscpy(device_info.name, name, len + 1);
679		ret = binderfs_binder_device_create(inode, NULL, &device_info);
680		if (ret)
681			return ret;
682		name += len;
683		if (*name == ',')
684			name++;
685	}
686
687	ret = init_binder_features(sb);
688	if (ret)
689		return ret;
690
691	if (info->mount_opts.stats_mode == binderfs_stats_mode_global)
692		return init_binder_logs(sb);
693
694	return 0;
695}
696
697static int binderfs_fs_context_get_tree(struct fs_context *fc)
698{
699	return get_tree_nodev(fc, binderfs_fill_super);
700}
701
702static void binderfs_fs_context_free(struct fs_context *fc)
703{
704	struct binderfs_mount_opts *ctx = fc->fs_private;
705
706	kfree(ctx);
707}
708
709static const struct fs_context_operations binderfs_fs_context_ops = {
710	.free		= binderfs_fs_context_free,
711	.get_tree	= binderfs_fs_context_get_tree,
712	.parse_param	= binderfs_fs_context_parse_param,
713	.reconfigure	= binderfs_fs_context_reconfigure,
714};
715
716static int binderfs_init_fs_context(struct fs_context *fc)
717{
718	struct binderfs_mount_opts *ctx;
719
720	ctx = kzalloc(sizeof(struct binderfs_mount_opts), GFP_KERNEL);
721	if (!ctx)
722		return -ENOMEM;
723
724	ctx->max = BINDERFS_MAX_MINOR;
725	ctx->stats_mode = binderfs_stats_mode_unset;
726
727	fc->fs_private = ctx;
728	fc->ops = &binderfs_fs_context_ops;
729
730	return 0;
731}
732
733static void binderfs_kill_super(struct super_block *sb)
734{
735	struct binderfs_info *info = sb->s_fs_info;
736
737	/*
738	 * During inode eviction struct binderfs_info is needed.
739	 * So first wipe the super_block then free struct binderfs_info.
740	 */
741	kill_anon_super(sb);
742
743	if (info && info->ipc_ns)
744		put_ipc_ns(info->ipc_ns);
745
746	kfree(info);
747}
748
749static struct file_system_type binder_fs_type = {
750	.name			= "binder",
751	.init_fs_context	= binderfs_init_fs_context,
752	.parameters		= binderfs_fs_parameters,
753	.kill_sb		= binderfs_kill_super,
754	.fs_flags		= FS_USERNS_MOUNT,
755};
756
757int __init init_binderfs(void)
758{
759	int ret;
760	const char *name;
761	size_t len;
762
763	/* Verify that the default binderfs device names are valid. */
764	name = binder_devices_param;
765	for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
766		if (len > BINDERFS_MAX_NAME)
767			return -E2BIG;
768		name += len;
769		if (*name == ',')
770			name++;
771	}
772
773	/* Allocate new major number for binderfs. */
774	ret = alloc_chrdev_region(&binderfs_dev, 0, BINDERFS_MAX_MINOR,
775				  "binder");
776	if (ret)
777		return ret;
778
779	ret = register_filesystem(&binder_fs_type);
780	if (ret) {
781		unregister_chrdev_region(binderfs_dev, BINDERFS_MAX_MINOR);
782		return ret;
783	}
784
785	return ret;
786}