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