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/mount.h> 17 #include <linux/init.h> 18 #include <linux/user_namespace.h> 19 20 #include "sysfs.h" 21 22 static struct kernfs_root *sysfs_root; 23 struct kernfs_node *sysfs_root_kn; 24 25 static struct dentry *sysfs_mount(struct file_system_type *fs_type, 26 int flags, const char *dev_name, void *data) 27 { 28 struct dentry *root; 29 void *ns; 30 31 if (!(flags & MS_KERNMOUNT)) { 32 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type)) 33 return ERR_PTR(-EPERM); 34 35 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET)) 36 return ERR_PTR(-EPERM); 37 } 38 39 ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET); 40 root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns); 41 if (IS_ERR(root)) 42 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns); 43 return root; 44 } 45 46 static 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 54 static 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 61 int __init sysfs_init(void) 62 { 63 int err; 64 65 sysfs_root = kernfs_create_root(NULL, NULL); 66 if (IS_ERR(sysfs_root)) 67 return PTR_ERR(sysfs_root); 68 69 sysfs_root_kn = sysfs_root->kn; 70 71 err = register_filesystem(&sysfs_fs_type); 72 if (err) { 73 kernfs_destroy_root(sysfs_root); 74 return err; 75 } 76 77 return 0; 78 } 79