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 bool new_sb; 31 32 if (!(flags & MS_KERNMOUNT)) { 33 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type)) 34 return ERR_PTR(-EPERM); 35 36 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET)) 37 return ERR_PTR(-EPERM); 38 } 39 40 ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET); 41 root = kernfs_mount_ns(fs_type, flags, sysfs_root, &new_sb, ns); 42 if (IS_ERR(root) || !new_sb) 43 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns); 44 return root; 45 } 46 47 static void sysfs_kill_sb(struct super_block *sb) 48 { 49 void *ns = (void *)kernfs_super_ns(sb); 50 51 kernfs_kill_sb(sb); 52 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns); 53 } 54 55 static struct file_system_type sysfs_fs_type = { 56 .name = "sysfs", 57 .mount = sysfs_mount, 58 .kill_sb = sysfs_kill_sb, 59 .fs_flags = FS_USERNS_MOUNT, 60 }; 61 62 int __init sysfs_init(void) 63 { 64 int err; 65 66 sysfs_root = kernfs_create_root(NULL, 0, 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 } 80