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1// SPDX-License-Identifier: GPL-2.02/*3 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs4 *5 * Copyright (c) 2001-3 Patrick Mochel6 * Copyright (c) 2007 SUSE Linux Products GmbH7 * 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}116