1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs 4 * 5 * Copyright (c) 2001-3 Patrick Mochel 6 * Copyright (c) 2007 SUSE Linux Products GmbH 7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de> 8 * 9 * Please see Documentation/filesystems/sysfs.txt for more information. 10 */ 11 12 #include <linux/fs.h> 13 #include <linux/magic.h> 14 #include <linux/mount.h> 15 #include <linux/init.h> 16 #include <linux/user_namespace.h> 17 18 #include "sysfs.h" 19 20 static struct kernfs_root *sysfs_root; 21 struct kernfs_node *sysfs_root_kn; 22 23 static struct dentry *sysfs_mount(struct file_system_type *fs_type, 24 int flags, const char *dev_name, void *data) 25 { 26 struct dentry *root; 27 void *ns; 28 bool new_sb = false; 29 30 if (!(flags & SB_KERNMOUNT)) { 31 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET)) 32 return ERR_PTR(-EPERM); 33 } 34 35 ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET); 36 root = kernfs_mount_ns(fs_type, flags, sysfs_root, 37 SYSFS_MAGIC, &new_sb, ns); 38 if (!new_sb) 39 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns); 40 else if (!IS_ERR(root)) 41 root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE; 42 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, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK, 66 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