1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Copyright (c) 2001-3 Patrick Mochel
6*4882a593Smuzhiyun * Copyright (c) 2007 SUSE Linux Products GmbH
7*4882a593Smuzhiyun * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8*4882a593Smuzhiyun *
9*4882a593Smuzhiyun * Please see Documentation/filesystems/sysfs.rst for more information.
10*4882a593Smuzhiyun */
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun #include <linux/fs.h>
13*4882a593Smuzhiyun #include <linux/magic.h>
14*4882a593Smuzhiyun #include <linux/mount.h>
15*4882a593Smuzhiyun #include <linux/init.h>
16*4882a593Smuzhiyun #include <linux/slab.h>
17*4882a593Smuzhiyun #include <linux/user_namespace.h>
18*4882a593Smuzhiyun #include <linux/fs_context.h>
19*4882a593Smuzhiyun #include <net/net_namespace.h>
20*4882a593Smuzhiyun
21*4882a593Smuzhiyun #include "sysfs.h"
22*4882a593Smuzhiyun
23*4882a593Smuzhiyun static struct kernfs_root *sysfs_root;
24*4882a593Smuzhiyun struct kernfs_node *sysfs_root_kn;
25*4882a593Smuzhiyun
sysfs_get_tree(struct fs_context * fc)26*4882a593Smuzhiyun static int sysfs_get_tree(struct fs_context *fc)
27*4882a593Smuzhiyun {
28*4882a593Smuzhiyun struct kernfs_fs_context *kfc = fc->fs_private;
29*4882a593Smuzhiyun int ret;
30*4882a593Smuzhiyun
31*4882a593Smuzhiyun ret = kernfs_get_tree(fc);
32*4882a593Smuzhiyun if (ret)
33*4882a593Smuzhiyun return ret;
34*4882a593Smuzhiyun
35*4882a593Smuzhiyun if (kfc->new_sb_created)
36*4882a593Smuzhiyun fc->root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
37*4882a593Smuzhiyun return 0;
38*4882a593Smuzhiyun }
39*4882a593Smuzhiyun
sysfs_fs_context_free(struct fs_context * fc)40*4882a593Smuzhiyun static void sysfs_fs_context_free(struct fs_context *fc)
41*4882a593Smuzhiyun {
42*4882a593Smuzhiyun struct kernfs_fs_context *kfc = fc->fs_private;
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun if (kfc->ns_tag)
45*4882a593Smuzhiyun kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);
46*4882a593Smuzhiyun kernfs_free_fs_context(fc);
47*4882a593Smuzhiyun kfree(kfc);
48*4882a593Smuzhiyun }
49*4882a593Smuzhiyun
50*4882a593Smuzhiyun static const struct fs_context_operations sysfs_fs_context_ops = {
51*4882a593Smuzhiyun .free = sysfs_fs_context_free,
52*4882a593Smuzhiyun .get_tree = sysfs_get_tree,
53*4882a593Smuzhiyun };
54*4882a593Smuzhiyun
sysfs_init_fs_context(struct fs_context * fc)55*4882a593Smuzhiyun static int sysfs_init_fs_context(struct fs_context *fc)
56*4882a593Smuzhiyun {
57*4882a593Smuzhiyun struct kernfs_fs_context *kfc;
58*4882a593Smuzhiyun struct net *netns;
59*4882a593Smuzhiyun
60*4882a593Smuzhiyun if (!(fc->sb_flags & SB_KERNMOUNT)) {
61*4882a593Smuzhiyun if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
62*4882a593Smuzhiyun return -EPERM;
63*4882a593Smuzhiyun }
64*4882a593Smuzhiyun
65*4882a593Smuzhiyun kfc = kzalloc(sizeof(struct kernfs_fs_context), GFP_KERNEL);
66*4882a593Smuzhiyun if (!kfc)
67*4882a593Smuzhiyun return -ENOMEM;
68*4882a593Smuzhiyun
69*4882a593Smuzhiyun kfc->ns_tag = netns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
70*4882a593Smuzhiyun kfc->root = sysfs_root;
71*4882a593Smuzhiyun kfc->magic = SYSFS_MAGIC;
72*4882a593Smuzhiyun fc->fs_private = kfc;
73*4882a593Smuzhiyun fc->ops = &sysfs_fs_context_ops;
74*4882a593Smuzhiyun if (netns) {
75*4882a593Smuzhiyun put_user_ns(fc->user_ns);
76*4882a593Smuzhiyun fc->user_ns = get_user_ns(netns->user_ns);
77*4882a593Smuzhiyun }
78*4882a593Smuzhiyun fc->global = true;
79*4882a593Smuzhiyun return 0;
80*4882a593Smuzhiyun }
81*4882a593Smuzhiyun
sysfs_kill_sb(struct super_block * sb)82*4882a593Smuzhiyun static void sysfs_kill_sb(struct super_block *sb)
83*4882a593Smuzhiyun {
84*4882a593Smuzhiyun void *ns = (void *)kernfs_super_ns(sb);
85*4882a593Smuzhiyun
86*4882a593Smuzhiyun kernfs_kill_sb(sb);
87*4882a593Smuzhiyun kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
88*4882a593Smuzhiyun }
89*4882a593Smuzhiyun
90*4882a593Smuzhiyun static struct file_system_type sysfs_fs_type = {
91*4882a593Smuzhiyun .name = "sysfs",
92*4882a593Smuzhiyun .init_fs_context = sysfs_init_fs_context,
93*4882a593Smuzhiyun .kill_sb = sysfs_kill_sb,
94*4882a593Smuzhiyun .fs_flags = FS_USERNS_MOUNT,
95*4882a593Smuzhiyun };
96*4882a593Smuzhiyun
sysfs_init(void)97*4882a593Smuzhiyun int __init sysfs_init(void)
98*4882a593Smuzhiyun {
99*4882a593Smuzhiyun int err;
100*4882a593Smuzhiyun
101*4882a593Smuzhiyun sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
102*4882a593Smuzhiyun NULL);
103*4882a593Smuzhiyun if (IS_ERR(sysfs_root))
104*4882a593Smuzhiyun return PTR_ERR(sysfs_root);
105*4882a593Smuzhiyun
106*4882a593Smuzhiyun sysfs_root_kn = sysfs_root->kn;
107*4882a593Smuzhiyun
108*4882a593Smuzhiyun err = register_filesystem(&sysfs_fs_type);
109*4882a593Smuzhiyun if (err) {
110*4882a593Smuzhiyun kernfs_destroy_root(sysfs_root);
111*4882a593Smuzhiyun return err;
112*4882a593Smuzhiyun }
113*4882a593Smuzhiyun
114*4882a593Smuzhiyun return 0;
115*4882a593Smuzhiyun }
116