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// 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 int sysfs_get_tree(struct fs_context *fc)
{
struct kernfs_fs_context *kfc = fc->fs_private;
int ret;
ret = kernfs_get_tree(fc);
if (ret)
return ret;
if (kfc->new_sb_created)
fc->root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
return 0;
}
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 = sysfs_get_tree,
};
static int sysfs_init_fs_context(struct fs_context *fc)
{
struct kernfs_fs_context *kfc;
struct net *netns;
if (!(fc->sb_flags & SB_KERNMOUNT)) {
if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
return -EPERM;
}
kfc = kzalloc(sizeof(struct kernfs_fs_context), GFP_KERNEL);
if (!kfc)
return -ENOMEM;
kfc->ns_tag = netns = 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 (netns) {
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)
{
void *ns = (void *)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,
};
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 = sysfs_root->kn;
err = register_filesystem(&sysfs_fs_type);
if (err) {
kernfs_destroy_root(sysfs_root);
return err;
}
return 0;
}
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