// SPDX-License-Identifier: GPL-2.0/* * fs/sysfs/symlink.c - operations for initializing and mounting sysfs * * Copyright (c) 2001-3 Patrick Mochel * Copyright (c) 2007 SUSE Linux Products GmbH * Copyright (c) 2007 Tejun Heo <teheo@suse.de> * * Please see Documentation/filesystems/sysfs.rst for more information. */ #include <linux/fs.h>#include <linux/magic.h>#include <linux/mount.h>#include <linux/init.h>#include <linux/slab.h>#include <linux/user_namespace.h>#include <linux/fs_context.h>#include <net/net_namespace.h> #include "sysfs.h" static struct kernfs_root *sysfs_root;struct kernfs_node *sysfs_root_kn; static void sysfs_fs_context_free(struct fs_context *fc){	struct kernfs_fs_context *kfc = fc->fs_private; 	if (kfc->ns_tag)		kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);	kernfs_free_fs_context(fc);	kfree(kfc);} static const struct fs_context_operations sysfs_fs_context_ops = {	.free		= sysfs_fs_context_free,	.get_tree	= kernfs_get_tree,}; static int sysfs_init_fs_context(struct fs_context *fc){	struct kernfs_fs_context *kfc;	struct ns_common *ns; 	if (!(fc->sb_flags & SB_KERNMOUNT)) {		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))			return -EPERM;	} 	kfc = kzalloc_obj(struct kernfs_fs_context);	if (!kfc)		return -ENOMEM; 	kfc->ns_tag = ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);	kfc->root = sysfs_root;	kfc->magic = SYSFS_MAGIC;	fc->fs_private = kfc;	fc->ops = &sysfs_fs_context_ops;	if (ns) {		struct net *netns = to_net_ns(ns); 		put_user_ns(fc->user_ns);		fc->user_ns = get_user_ns(netns->user_ns);	}	fc->global = true;	return 0;} static void sysfs_kill_sb(struct super_block *sb){	struct ns_common *ns = (struct ns_common *)kernfs_super_ns(sb); 	kernfs_kill_sb(sb);	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);} static struct file_system_type sysfs_fs_type = {	.name			= "sysfs",	.init_fs_context	= sysfs_init_fs_context,	.kill_sb		= sysfs_kill_sb,	.fs_flags		= FS_USERNS_MOUNT | FS_USERNS_MOUNT_RESTRICTED,}; int __init sysfs_init(void){	int err; 	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,					NULL);	if (IS_ERR(sysfs_root))		return PTR_ERR(sysfs_root); 	sysfs_root_kn = kernfs_root_to_node(sysfs_root); 	err = register_filesystem(&sysfs_fs_type);	if (err) {		kernfs_destroy_root(sysfs_root);		return err;	} 	return 0;}