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 sysfs_dirent *sysfs_root_sd; 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 kernfs_kill_sb(sb); 49 kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)kernfs_super_ns(sb)); 50 } 51 52 static struct file_system_type sysfs_fs_type = { 53 .name = "sysfs", 54 .mount = sysfs_mount, 55 .kill_sb = sysfs_kill_sb, 56 .fs_flags = FS_USERNS_MOUNT, 57 }; 58 59 int __init sysfs_init(void) 60 { 61 int err; 62 63 sysfs_root = kernfs_create_root(NULL); 64 if (IS_ERR(sysfs_root)) 65 return PTR_ERR(sysfs_root); 66 67 sysfs_root_sd = sysfs_root->sd; 68 69 err = register_filesystem(&sysfs_fs_type); 70 if (err) { 71 kernfs_destroy_root(sysfs_root); 72 return err; 73 } 74 75 return 0; 76 } 77