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
23 static struct kernfs_root *sysfs_root;
24 struct kernfs_node *sysfs_root_kn;
25
sysfs_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)26 static 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 (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
35 return ERR_PTR(-EPERM);
36 }
37
38 ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
39 root = kernfs_mount_ns(fs_type, flags, sysfs_root,
40 SYSFS_MAGIC, &new_sb, ns);
41 if (IS_ERR(root) || !new_sb)
42 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
43 else if (new_sb)
44 /* Userspace would break if executables appear on sysfs */
45 root->d_sb->s_iflags |= SB_I_NOEXEC;
46
47 return root;
48 }
49
sysfs_kill_sb(struct super_block * sb)50 static void sysfs_kill_sb(struct super_block *sb)
51 {
52 void *ns = (void *)kernfs_super_ns(sb);
53
54 kernfs_kill_sb(sb);
55 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
56 }
57
58 static struct file_system_type sysfs_fs_type = {
59 .name = "sysfs",
60 .mount = sysfs_mount,
61 .kill_sb = sysfs_kill_sb,
62 .fs_flags = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
63 };
64
sysfs_init(void)65 int __init sysfs_init(void)
66 {
67 int err;
68
69 sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
70 NULL);
71 if (IS_ERR(sysfs_root))
72 return PTR_ERR(sysfs_root);
73
74 sysfs_root_kn = sysfs_root->kn;
75
76 err = register_filesystem(&sysfs_fs_type);
77 if (err) {
78 kernfs_destroy_root(sysfs_root);
79 return err;
80 }
81
82 return 0;
83 }
84