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};
62
63static const struct constant_table binderfs_param_stats[] = {
64 { "global", binderfs_stats_mode_global },
65 {}
66};
67
68static const struct fs_parameter_spec binderfs_fs_parameters[] = {
69 fsparam_u32("max", Opt_max),
70 fsparam_enum("stats", Opt_stats_mode, binderfs_param_stats),
71 {}
72};
73
74static struct binder_features binder_features = {
75 .oneway_spam_detection = true,
76 .extended_error = true,
77};
78
79static inline struct binderfs_info *BINDERFS_SB(const struct super_block *sb)
80{
81 return sb->s_fs_info;
82}
83
84bool is_binderfs_device(const struct inode *inode)
85{
86 if (inode->i_sb->s_magic == BINDERFS_SUPER_MAGIC)
87 return true;
88
89 return false;
90}
91
92/**
93 * binderfs_binder_device_create - allocate inode from super block of a
94 * binderfs mount
95 * @ref_inode: inode from which the super block will be taken
96 * @userp: buffer to copy information about new device for userspace to
97 * @req: struct binderfs_device as copied from userspace
98 *
99 * This function allocates a new binder_device and reserves a new minor
100 * number for it.
101 * Minor numbers are limited and tracked globally in binderfs_minors. The
102 * function will stash a struct binder_device for the specific binder
103 * device in i_private of the inode.
104 * It will go on to allocate a new inode from the super block of the
105 * filesystem mount, stash a struct binder_device in its i_private field
106 * and attach a dentry to that inode.
107 *
108 * Return: 0 on success, negative errno on failure
109 */
110static int binderfs_binder_device_create(struct inode *ref_inode,
111 struct binderfs_device __user *userp,
112 struct binderfs_device *req)
113{
114 int minor, ret;
115 struct dentry *dentry, *root;
116 struct binder_device *device;
117 char *name = NULL;
118 size_t name_len;
119 struct inode *inode = NULL;
120 struct super_block *sb = ref_inode->i_sb;
121 struct binderfs_info *info = sb->s_fs_info;
122#if defined(CONFIG_IPC_NS)
123 bool use_reserve = (info->ipc_ns == &init_ipc_ns);
124#else
125 bool use_reserve = true;
126#endif
127
128 /* Reserve new minor number for the new device. */
129 mutex_lock(&binderfs_minors_mutex);
130 if (++info->device_count <= info->mount_opts.max)
131 minor = ida_alloc_max(ida: &binderfs_minors,
132 max: use_reserve ? BINDERFS_MAX_MINOR :
133 BINDERFS_MAX_MINOR_CAPPED,
134 GFP_KERNEL);
135 else
136 minor = -ENOSPC;
137 if (minor < 0) {
138 --info->device_count;
139 mutex_unlock(lock: &binderfs_minors_mutex);
140 return minor;
141 }
142 mutex_unlock(lock: &binderfs_minors_mutex);
143
144 ret = -ENOMEM;
145 device = kzalloc(size: sizeof(*device), GFP_KERNEL);
146 if (!device)
147 goto err;
148
149 inode = new_inode(sb);
150 if (!inode)
151 goto err;
152
153 inode->i_ino = minor + INODE_OFFSET;
154 simple_inode_init_ts(inode);
155 init_special_inode(inode, S_IFCHR | 0600,
156 MKDEV(MAJOR(binderfs_dev), minor));
157 inode->i_fop = &binder_fops;
158 inode->i_uid = info->root_uid;
159 inode->i_gid = info->root_gid;
160
161 req->name[BINDERFS_MAX_NAME] = '\0'; /* NUL-terminate */
162 name_len = strlen(req->name);
163 /* Make sure to include terminating NUL byte */
164 name = kmemdup(p: req->name, size: name_len + 1, GFP_KERNEL);
165 if (!name)
166 goto err;
167
168 refcount_set(r: &device->ref, n: 1);
169 device->binderfs_inode = inode;
170 device->context.binder_context_mgr_uid = INVALID_UID;
171 device->context.name = name;
172 device->miscdev.name = name;
173 device->miscdev.minor = minor;
174 mutex_init(&device->context.context_mgr_node_lock);
175
176 req->major = MAJOR(binderfs_dev);
177 req->minor = minor;
178
179 if (userp && copy_to_user(to: userp, from: req, n: sizeof(*req))) {
180 ret = -EFAULT;
181 goto err;
182 }
183
184 root = sb->s_root;
185 inode_lock(inode: d_inode(dentry: root));
186
187 /* look it up */
188 dentry = lookup_one_len(name, root, name_len);
189 if (IS_ERR(ptr: dentry)) {
190 inode_unlock(inode: d_inode(dentry: root));
191 ret = PTR_ERR(ptr: dentry);
192 goto err;
193 }
194
195 if (d_really_is_positive(dentry)) {
196 /* already exists */
197 dput(dentry);
198 inode_unlock(inode: d_inode(dentry: root));
199 ret = -EEXIST;
200 goto err;
201 }
202
203 inode->i_private = device;
204 d_instantiate(dentry, inode);
205 fsnotify_create(dir: root->d_inode, dentry);
206 inode_unlock(inode: d_inode(dentry: root));
207
208 return 0;
209
210err:
211 kfree(objp: name);
212 kfree(objp: device);
213 mutex_lock(&binderfs_minors_mutex);
214 --info->device_count;
215 ida_free(&binderfs_minors, id: minor);
216 mutex_unlock(lock: &binderfs_minors_mutex);
217 iput(inode);
218
219 return ret;
220}
221
222/**
223 * binder_ctl_ioctl - handle binder device node allocation requests
224 *
225 * The request handler for the binder-control device. All requests operate on
226 * the binderfs mount the binder-control device resides in:
227 * - BINDER_CTL_ADD
228 * Allocate a new binder device.
229 *
230 * Return: %0 on success, negative errno on failure.
231 */
232static long binder_ctl_ioctl(struct file *file, unsigned int cmd,
233 unsigned long arg)
234{
235 int ret = -EINVAL;
236 struct inode *inode = file_inode(f: file);
237 struct binderfs_device __user *device = (struct binderfs_device __user *)arg;
238 struct binderfs_device device_req;
239
240 switch (cmd) {
241 case BINDER_CTL_ADD:
242 ret = copy_from_user(to: &device_req, from: device, n: sizeof(device_req));
243 if (ret) {
244 ret = -EFAULT;
245 break;
246 }
247
248 ret = binderfs_binder_device_create(ref_inode: inode, userp: device, req: &device_req);
249 break;
250 default:
251 break;
252 }
253
254 return ret;
255}
256
257static void binderfs_evict_inode(struct inode *inode)
258{
259 struct binder_device *device = inode->i_private;
260 struct binderfs_info *info = BINDERFS_SB(sb: inode->i_sb);
261
262 clear_inode(inode);
263
264 if (!S_ISCHR(inode->i_mode) || !device)
265 return;
266
267 mutex_lock(&binderfs_minors_mutex);
268 --info->device_count;
269 ida_free(&binderfs_minors, id: device->miscdev.minor);
270 mutex_unlock(lock: &binderfs_minors_mutex);
271
272 if (refcount_dec_and_test(r: &device->ref)) {
273 kfree(objp: device->context.name);
274 kfree(objp: device);
275 }
276}
277
278static int binderfs_fs_context_parse_param(struct fs_context *fc,
279 struct fs_parameter *param)
280{
281 int opt;
282 struct binderfs_mount_opts *ctx = fc->fs_private;
283 struct fs_parse_result result;
284
285 opt = fs_parse(fc, desc: binderfs_fs_parameters, param, result: &result);
286 if (opt < 0)
287 return opt;
288
289 switch (opt) {
290 case Opt_max:
291 if (result.uint_32 > BINDERFS_MAX_MINOR)
292 return invalfc(fc, "Bad value for '%s'", param->key);
293
294 ctx->max = result.uint_32;
295 break;
296 case Opt_stats_mode:
297 if (!capable(CAP_SYS_ADMIN))
298 return -EPERM;
299
300 ctx->stats_mode = result.uint_32;
301 break;
302 default:
303 return invalfc(fc, "Unsupported parameter '%s'", param->key);
304 }
305
306 return 0;
307}
308
309static int binderfs_fs_context_reconfigure(struct fs_context *fc)
310{
311 struct binderfs_mount_opts *ctx = fc->fs_private;
312 struct binderfs_info *info = BINDERFS_SB(sb: fc->root->d_sb);
313
314 if (info->mount_opts.stats_mode != ctx->stats_mode)
315 return invalfc(fc, "Binderfs stats mode cannot be changed during a remount");
316
317 info->mount_opts.stats_mode = ctx->stats_mode;
318 info->mount_opts.max = ctx->max;
319 return 0;
320}
321
322static int binderfs_show_options(struct seq_file *seq, struct dentry *root)
323{
324 struct binderfs_info *info = BINDERFS_SB(sb: root->d_sb);
325
326 if (info->mount_opts.max <= BINDERFS_MAX_MINOR)
327 seq_printf(m: seq, fmt: ",max=%d", info->mount_opts.max);
328
329 switch (info->mount_opts.stats_mode) {
330 case binderfs_stats_mode_unset:
331 break;
332 case binderfs_stats_mode_global:
333 seq_printf(m: seq, fmt: ",stats=global");
334 break;
335 }
336
337 return 0;
338}
339
340static const struct super_operations binderfs_super_ops = {
341 .evict_inode = binderfs_evict_inode,
342 .show_options = binderfs_show_options,
343 .statfs = simple_statfs,
344};
345
346static inline bool is_binderfs_control_device(const struct dentry *dentry)
347{
348 struct binderfs_info *info = dentry->d_sb->s_fs_info;
349
350 return info->control_dentry == dentry;
351}
352
353static int binderfs_rename(struct mnt_idmap *idmap,
354 struct inode *old_dir, struct dentry *old_dentry,
355 struct inode *new_dir, struct dentry *new_dentry,
356 unsigned int flags)
357{
358 if (is_binderfs_control_device(dentry: old_dentry) ||
359 is_binderfs_control_device(dentry: new_dentry))
360 return -EPERM;
361
362 return simple_rename(idmap, old_dir, old_dentry, new_dir,
363 new_dentry, flags);
364}
365
366static int binderfs_unlink(struct inode *dir, struct dentry *dentry)
367{
368 if (is_binderfs_control_device(dentry))
369 return -EPERM;
370
371 return simple_unlink(dir, dentry);
372}
373
374static const struct file_operations binder_ctl_fops = {
375 .owner = THIS_MODULE,
376 .open = nonseekable_open,
377 .unlocked_ioctl = binder_ctl_ioctl,
378 .compat_ioctl = binder_ctl_ioctl,
379 .llseek = noop_llseek,
380};
381
382/**
383 * binderfs_binder_ctl_create - create a new binder-control device
384 * @sb: super block of the binderfs mount
385 *
386 * This function creates a new binder-control device node in the binderfs mount
387 * referred to by @sb.
388 *
389 * Return: 0 on success, negative errno on failure
390 */
391static int binderfs_binder_ctl_create(struct super_block *sb)
392{
393 int minor, ret;
394 struct dentry *dentry;
395 struct binder_device *device;
396 struct inode *inode = NULL;
397 struct dentry *root = sb->s_root;
398 struct binderfs_info *info = sb->s_fs_info;
399#if defined(CONFIG_IPC_NS)
400 bool use_reserve = (info->ipc_ns == &init_ipc_ns);
401#else
402 bool use_reserve = true;
403#endif
404
405 device = kzalloc(size: sizeof(*device), GFP_KERNEL);
406 if (!device)
407 return -ENOMEM;
408
409 /* If we have already created a binder-control node, return. */
410 if (info->control_dentry) {
411 ret = 0;
412 goto out;
413 }
414
415 ret = -ENOMEM;
416 inode = new_inode(sb);
417 if (!inode)
418 goto out;
419
420 /* Reserve a new minor number for the new device. */
421 mutex_lock(&binderfs_minors_mutex);
422 minor = ida_alloc_max(ida: &binderfs_minors,
423 max: use_reserve ? BINDERFS_MAX_MINOR :
424 BINDERFS_MAX_MINOR_CAPPED,
425 GFP_KERNEL);
426 mutex_unlock(lock: &binderfs_minors_mutex);
427 if (minor < 0) {
428 ret = minor;
429 goto out;
430 }
431
432 inode->i_ino = SECOND_INODE;
433 simple_inode_init_ts(inode);
434 init_special_inode(inode, S_IFCHR | 0600,
435 MKDEV(MAJOR(binderfs_dev), minor));
436 inode->i_fop = &binder_ctl_fops;
437 inode->i_uid = info->root_uid;
438 inode->i_gid = info->root_gid;
439
440 refcount_set(r: &device->ref, n: 1);
441 device->binderfs_inode = inode;
442 device->miscdev.minor = minor;
443
444 dentry = d_alloc_name(root, "binder-control");
445 if (!dentry)
446 goto out;
447
448 inode->i_private = device;
449 info->control_dentry = dentry;
450 d_add(dentry, inode);
451
452 return 0;
453
454out:
455 kfree(objp: device);
456 iput(inode);
457
458 return ret;
459}
460
461static const struct inode_operations binderfs_dir_inode_operations = {
462 .lookup = simple_lookup,
463 .rename = binderfs_rename,
464 .unlink = binderfs_unlink,
465};
466
467static struct inode *binderfs_make_inode(struct super_block *sb, int mode)
468{
469 struct inode *ret;
470
471 ret = new_inode(sb);
472 if (ret) {
473 ret->i_ino = iunique(sb, BINDERFS_MAX_MINOR + INODE_OFFSET);
474 ret->i_mode = mode;
475 simple_inode_init_ts(inode: ret);
476 }
477 return ret;
478}
479
480static struct dentry *binderfs_create_dentry(struct dentry *parent,
481 const char *name)
482{
483 struct dentry *dentry;
484
485 dentry = lookup_one_len(name, parent, strlen(name));
486 if (IS_ERR(ptr: dentry))
487 return dentry;
488
489 /* Return error if the file/dir already exists. */
490 if (d_really_is_positive(dentry)) {
491 dput(dentry);
492 return ERR_PTR(error: -EEXIST);
493 }
494
495 return dentry;
496}
497
498void binderfs_remove_file(struct dentry *dentry)
499{
500 struct inode *parent_inode;
501
502 parent_inode = d_inode(dentry: dentry->d_parent);
503 inode_lock(inode: parent_inode);
504 if (simple_positive(dentry)) {
505 dget(dentry);
506 simple_unlink(parent_inode, dentry);
507 d_delete(dentry);
508 dput(dentry);
509 }
510 inode_unlock(inode: parent_inode);
511}
512
513struct dentry *binderfs_create_file(struct dentry *parent, const char *name,
514 const struct file_operations *fops,
515 void *data)
516{
517 struct dentry *dentry;
518 struct inode *new_inode, *parent_inode;
519 struct super_block *sb;
520
521 parent_inode = d_inode(dentry: parent);
522 inode_lock(inode: parent_inode);
523
524 dentry = binderfs_create_dentry(parent, name);
525 if (IS_ERR(ptr: dentry))
526 goto out;
527
528 sb = parent_inode->i_sb;
529 new_inode = binderfs_make_inode(sb, S_IFREG | 0444);
530 if (!new_inode) {
531 dput(dentry);
532 dentry = ERR_PTR(error: -ENOMEM);
533 goto out;
534 }
535
536 new_inode->i_fop = fops;
537 new_inode->i_private = data;
538 d_instantiate(dentry, new_inode);
539 fsnotify_create(dir: parent_inode, dentry);
540
541out:
542 inode_unlock(inode: parent_inode);
543 return dentry;
544}
545
546static struct dentry *binderfs_create_dir(struct dentry *parent,
547 const char *name)
548{
549 struct dentry *dentry;
550 struct inode *new_inode, *parent_inode;
551 struct super_block *sb;
552
553 parent_inode = d_inode(dentry: parent);
554 inode_lock(inode: parent_inode);
555
556 dentry = binderfs_create_dentry(parent, name);
557 if (IS_ERR(ptr: dentry))
558 goto out;
559
560 sb = parent_inode->i_sb;
561 new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);
562 if (!new_inode) {
563 dput(dentry);
564 dentry = ERR_PTR(error: -ENOMEM);
565 goto out;
566 }
567
568 new_inode->i_fop = &simple_dir_operations;
569 new_inode->i_op = &simple_dir_inode_operations;
570
571 set_nlink(inode: new_inode, nlink: 2);
572 d_instantiate(dentry, new_inode);
573 inc_nlink(inode: parent_inode);
574 fsnotify_mkdir(dir: parent_inode, dentry);
575
576out:
577 inode_unlock(inode: parent_inode);
578 return dentry;
579}
580
581static int binder_features_show(struct seq_file *m, void *unused)
582{
583 bool *feature = m->private;
584
585 seq_printf(m, fmt: "%d\n", *feature);
586
587 return 0;
588}
589DEFINE_SHOW_ATTRIBUTE(binder_features);
590
591static int init_binder_features(struct super_block *sb)
592{
593 struct dentry *dentry, *dir;
594
595 dir = binderfs_create_dir(parent: sb->s_root, name: "features");
596 if (IS_ERR(ptr: dir))
597 return PTR_ERR(ptr: dir);
598
599 dentry = binderfs_create_file(parent: dir, name: "oneway_spam_detection",
600 fops: &binder_features_fops,
601 data: &binder_features.oneway_spam_detection);
602 if (IS_ERR(ptr: dentry))
603 return PTR_ERR(ptr: dentry);
604
605 dentry = binderfs_create_file(parent: dir, name: "extended_error",
606 fops: &binder_features_fops,
607 data: &binder_features.extended_error);
608 if (IS_ERR(ptr: dentry))
609 return PTR_ERR(ptr: dentry);
610
611 return 0;
612}
613
614static int init_binder_logs(struct super_block *sb)
615{
616 struct dentry *binder_logs_root_dir, *dentry, *proc_log_dir;
617 const struct binder_debugfs_entry *db_entry;
618 struct binderfs_info *info;
619 int ret = 0;
620
621 binder_logs_root_dir = binderfs_create_dir(parent: sb->s_root,
622 name: "binder_logs");
623 if (IS_ERR(ptr: binder_logs_root_dir)) {
624 ret = PTR_ERR(ptr: binder_logs_root_dir);
625 goto out;
626 }
627
628 binder_for_each_debugfs_entry(db_entry) {
629 dentry = binderfs_create_file(parent: binder_logs_root_dir,
630 name: db_entry->name,
631 fops: db_entry->fops,
632 data: db_entry->data);
633 if (IS_ERR(ptr: dentry)) {
634 ret = PTR_ERR(ptr: dentry);
635 goto out;
636 }
637 }
638
639 proc_log_dir = binderfs_create_dir(parent: binder_logs_root_dir, name: "proc");
640 if (IS_ERR(ptr: proc_log_dir)) {
641 ret = PTR_ERR(ptr: proc_log_dir);
642 goto out;
643 }
644 info = sb->s_fs_info;
645 info->proc_log_dir = proc_log_dir;
646
647out:
648 return ret;
649}
650
651static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc)
652{
653 int ret;
654 struct binderfs_info *info;
655 struct binderfs_mount_opts *ctx = fc->fs_private;
656 struct inode *inode = NULL;
657 struct binderfs_device device_info = {};
658 const char *name;
659 size_t len;
660
661 sb->s_blocksize = PAGE_SIZE;
662 sb->s_blocksize_bits = PAGE_SHIFT;
663
664 /*
665 * The binderfs filesystem can be mounted by userns root in a
666 * non-initial userns. By default such mounts have the SB_I_NODEV flag
667 * set in s_iflags to prevent security issues where userns root can
668 * just create random device nodes via mknod() since it owns the
669 * filesystem mount. But binderfs does not allow to create any files
670 * including devices nodes. The only way to create binder devices nodes
671 * is through the binder-control device which userns root is explicitly
672 * allowed to do. So removing the SB_I_NODEV flag from s_iflags is both
673 * necessary and safe.
674 */
675 sb->s_iflags &= ~SB_I_NODEV;
676 sb->s_iflags |= SB_I_NOEXEC;
677 sb->s_magic = BINDERFS_SUPER_MAGIC;
678 sb->s_op = &binderfs_super_ops;
679 sb->s_time_gran = 1;
680
681 sb->s_fs_info = kzalloc(size: sizeof(struct binderfs_info), GFP_KERNEL);
682 if (!sb->s_fs_info)
683 return -ENOMEM;
684 info = sb->s_fs_info;
685
686 info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
687
688 info->root_gid = make_kgid(from: sb->s_user_ns, gid: 0);
689 if (!gid_valid(gid: info->root_gid))
690 info->root_gid = GLOBAL_ROOT_GID;
691 info->root_uid = make_kuid(sb->s_user_ns, 0);
692 if (!uid_valid(info->root_uid))
693 info->root_uid = GLOBAL_ROOT_UID;
694 info->mount_opts.max = ctx->max;
695 info->mount_opts.stats_mode = ctx->stats_mode;
696
697 inode = new_inode(sb);
698 if (!inode)
699 return -ENOMEM;
700
701 inode->i_ino = FIRST_INODE;
702 inode->i_fop = &simple_dir_operations;
703 inode->i_mode = S_IFDIR | 0755;
704 simple_inode_init_ts(inode);
705 inode->i_op = &binderfs_dir_inode_operations;
706 set_nlink(inode, 2);
707
708 sb->s_root = d_make_root(inode);
709 if (!sb->s_root)
710 return -ENOMEM;
711
712 ret = binderfs_binder_ctl_create(sb);
713 if (ret)
714 return ret;
715
716 name = binder_devices_param;
717 for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
718 strscpy(device_info.name, name, len + 1);
719 ret = binderfs_binder_device_create(inode, NULL, &device_info);
720 if (ret)
721 return ret;
722 name += len;
723 if (*name == ',')
724 name++;
725 }
726
727 ret = init_binder_features(sb);
728 if (ret)
729 return ret;
730
731 if (info->mount_opts.stats_mode == binderfs_stats_mode_global)
732 return init_binder_logs(sb);
733
734 return 0;
735}
736
737static int binderfs_fs_context_get_tree(struct fs_context *fc)
738{
739 return get_tree_nodev(fc, fill_super: binderfs_fill_super);
740}
741
742static void binderfs_fs_context_free(struct fs_context *fc)
743{
744 struct binderfs_mount_opts *ctx = fc->fs_private;
745
746 kfree(objp: ctx);
747}
748
749static const struct fs_context_operations binderfs_fs_context_ops = {
750 .free = binderfs_fs_context_free,
751 .get_tree = binderfs_fs_context_get_tree,
752 .parse_param = binderfs_fs_context_parse_param,
753 .reconfigure = binderfs_fs_context_reconfigure,
754};
755
756static int binderfs_init_fs_context(struct fs_context *fc)
757{
758 struct binderfs_mount_opts *ctx;
759
760 ctx = kzalloc(size: sizeof(struct binderfs_mount_opts), GFP_KERNEL);
761 if (!ctx)
762 return -ENOMEM;
763
764 ctx->max = BINDERFS_MAX_MINOR;
765 ctx->stats_mode = binderfs_stats_mode_unset;
766
767 fc->fs_private = ctx;
768 fc->ops = &binderfs_fs_context_ops;
769
770 return 0;
771}
772
773static void binderfs_kill_super(struct super_block *sb)
774{
775 struct binderfs_info *info = sb->s_fs_info;
776
777 /*
778 * During inode eviction struct binderfs_info is needed.
779 * So first wipe the super_block then free struct binderfs_info.
780 */
781 kill_litter_super(sb);
782
783 if (info && info->ipc_ns)
784 put_ipc_ns(ns: info->ipc_ns);
785
786 kfree(objp: info);
787}
788
789static struct file_system_type binder_fs_type = {
790 .name = "binder",
791 .init_fs_context = binderfs_init_fs_context,
792 .parameters = binderfs_fs_parameters,
793 .kill_sb = binderfs_kill_super,
794 .fs_flags = FS_USERNS_MOUNT,
795};
796
797int __init init_binderfs(void)
798{
799 int ret;
800 const char *name;
801 size_t len;
802
803 /* Verify that the default binderfs device names are valid. */
804 name = binder_devices_param;
805 for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
806 if (len > BINDERFS_MAX_NAME)
807 return -E2BIG;
808 name += len;
809 if (*name == ',')
810 name++;
811 }
812
813 /* Allocate new major number for binderfs. */
814 ret = alloc_chrdev_region(&binderfs_dev, 0, BINDERFS_MAX_MINOR,
815 "binder");
816 if (ret)
817 return ret;
818
819 ret = register_filesystem(&binder_fs_type);
820 if (ret) {
821 unregister_chrdev_region(binderfs_dev, BINDERFS_MAX_MINOR);
822 return ret;
823 }
824
825 return ret;
826}
827

source code of linux/drivers/android/binderfs.c