1/*
 2 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
 3 *
 4 * Copyright (c) 2001-3 Patrick Mochel
 5 * Copyright (c) 2007 SUSE Linux Products GmbH
 6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 7 *
 8 * This file is released under the GPLv2.
 9 *
10 * Please see Documentation/filesystems/sysfs.txt for more information.
11 */
12
13#define DEBUG
14
15#include <linux/fs.h>
16#include <linux/magic.h>
17#include <linux/mount.h>
18#include <linux/init.h>
19#include <linux/user_namespace.h>
20
21#include "sysfs.h"
22
23static struct kernfs_root *sysfs_root;
24struct kernfs_node *sysfs_root_kn;
25
26static struct dentry *sysfs_mount(struct file_system_type *fs_type,
27	int flags, const char *dev_name, void *data)
28{
29	struct dentry *root;
30	void *ns;
31	bool new_sb;
32
33	if (!(flags & MS_KERNMOUNT)) {
34		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
35			return ERR_PTR(-EPERM);
36
 
37		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
38			return ERR_PTR(-EPERM);
39	}
40
41	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
42	root = kernfs_mount_ns(fs_type, flags, sysfs_root,
43				SYSFS_MAGIC, &new_sb, ns);
44	if (IS_ERR(root) || !new_sb)
45		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 
 
 
46	return root;
47}
48
49static void sysfs_kill_sb(struct super_block *sb)
50{
51	void *ns = (void *)kernfs_super_ns(sb);
52
53	kernfs_kill_sb(sb);
54	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
55}
56
57static struct file_system_type sysfs_fs_type = {
58	.name		= "sysfs",
59	.mount		= sysfs_mount,
60	.kill_sb	= sysfs_kill_sb,
61	.fs_flags	= FS_USERNS_MOUNT,
62};
63
64int __init sysfs_init(void)
65{
66	int err;
67
68	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
69					NULL);
70	if (IS_ERR(sysfs_root))
71		return PTR_ERR(sysfs_root);
72
73	sysfs_root_kn = sysfs_root->kn;
74
75	err = register_filesystem(&sysfs_fs_type);
76	if (err) {
77		kernfs_destroy_root(sysfs_root);
78		return err;
79	}
80
81	return 0;
82}

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
 4 *
 5 * Copyright (c) 2001-3 Patrick Mochel
 6 * Copyright (c) 2007 SUSE Linux Products GmbH
 7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 8 *
 
 
 9 * Please see Documentation/filesystems/sysfs.txt for more information.
10 */
11
 
 
12#include <linux/fs.h>
13#include <linux/magic.h>
14#include <linux/mount.h>
15#include <linux/init.h>
16#include <linux/user_namespace.h>
17
18#include "sysfs.h"
19
20static struct kernfs_root *sysfs_root;
21struct kernfs_node *sysfs_root_kn;
22
23static struct dentry *sysfs_mount(struct file_system_type *fs_type,
24	int flags, const char *dev_name, void *data)
25{
26	struct dentry *root;
27	void *ns;
28	bool new_sb = false;
 
 
 
 
29
30	if (!(flags & SB_KERNMOUNT)) {
31		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
32			return ERR_PTR(-EPERM);
33	}
34
35	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
36	root = kernfs_mount_ns(fs_type, flags, sysfs_root,
37				SYSFS_MAGIC, &new_sb, ns);
38	if (!new_sb)
39		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
40	else if (!IS_ERR(root))
41		root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
42
43	return root;
44}
45
46static void sysfs_kill_sb(struct super_block *sb)
47{
48	void *ns = (void *)kernfs_super_ns(sb);
49
50	kernfs_kill_sb(sb);
51	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
52}
53
54static struct file_system_type sysfs_fs_type = {
55	.name		= "sysfs",
56	.mount		= sysfs_mount,
57	.kill_sb	= sysfs_kill_sb,
58	.fs_flags	= FS_USERNS_MOUNT,
59};
60
61int __init sysfs_init(void)
62{
63	int err;
64
65	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
66					NULL);
67	if (IS_ERR(sysfs_root))
68		return PTR_ERR(sysfs_root);
69
70	sysfs_root_kn = sysfs_root->kn;
71
72	err = register_filesystem(&sysfs_fs_type);
73	if (err) {
74		kernfs_destroy_root(sysfs_root);
75		return err;
76	}
77
78	return 0;
79}