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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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