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 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 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 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