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.rst 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/slab.h>
 17#include <linux/user_namespace.h>
 18#include <linux/fs_context.h>
 19#include <net/net_namespace.h>
 20
 21#include "sysfs.h"
 22
 23static struct kernfs_root *sysfs_root;
 24struct kernfs_node *sysfs_root_kn;
 25
 26static int sysfs_get_tree(struct fs_context *fc)
 27{
 28	struct kernfs_fs_context *kfc = fc->fs_private;
 29	int ret;
 30
 31	ret = kernfs_get_tree(fc);
 32	if (ret)
 33		return ret;
 34
 35	if (kfc->new_sb_created)
 36		fc->root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
 37	return 0;
 38}
 39
 40static void sysfs_fs_context_free(struct fs_context *fc)
 41{
 42	struct kernfs_fs_context *kfc = fc->fs_private;
 43
 44	if (kfc->ns_tag)
 45		kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);
 46	kernfs_free_fs_context(fc);
 47	kfree(kfc);
 48}
 49
 50static const struct fs_context_operations sysfs_fs_context_ops = {
 51	.free		= sysfs_fs_context_free,
 52	.get_tree	= sysfs_get_tree,
 53};
 54
 55static int sysfs_init_fs_context(struct fs_context *fc)
 56{
 57	struct kernfs_fs_context *kfc;
 58	struct net *netns;
 
 59
 60	if (!(fc->sb_flags & SB_KERNMOUNT)) {
 61		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
 62			return -EPERM;
 63	}
 64
 65	kfc = kzalloc(sizeof(struct kernfs_fs_context), GFP_KERNEL);
 66	if (!kfc)
 67		return -ENOMEM;
 68
 69	kfc->ns_tag = netns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
 70	kfc->root = sysfs_root;
 71	kfc->magic = SYSFS_MAGIC;
 72	fc->fs_private = kfc;
 73	fc->ops = &sysfs_fs_context_ops;
 74	if (netns) {
 75		put_user_ns(fc->user_ns);
 76		fc->user_ns = get_user_ns(netns->user_ns);
 77	}
 78	fc->global = true;
 79	return 0;
 80}
 81
 82static void sysfs_kill_sb(struct super_block *sb)
 83{
 84	void *ns = (void *)kernfs_super_ns(sb);
 85
 86	kernfs_kill_sb(sb);
 87	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 88}
 89
 90static struct file_system_type sysfs_fs_type = {
 91	.name			= "sysfs",
 92	.init_fs_context	= sysfs_init_fs_context,
 93	.kill_sb		= sysfs_kill_sb,
 94	.fs_flags		= FS_USERNS_MOUNT,
 95};
 96
 97int __init sysfs_init(void)
 98{
 99	int err;
100
101	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
102					NULL);
103	if (IS_ERR(sysfs_root))
104		return PTR_ERR(sysfs_root);
105
106	sysfs_root_kn = kernfs_root_to_node(sysfs_root);
107
108	err = register_filesystem(&sysfs_fs_type);
109	if (err) {
110		kernfs_destroy_root(sysfs_root);
111		return err;
112	}
113
114	return 0;
115}

 
 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
23static struct kernfs_root *sysfs_root;
24struct kernfs_node *sysfs_root_kn;
25
26static 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
50static 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
58static 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
65int __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}