/* *  This program is free software; you can redistribute it and/or *  modify it under the terms of the GNU General Public License as *  published by the Free Software Foundation, version 2 of the *  License. */ #include <linux/module.h>#include <linux/version.h>#include <linux/nsproxy.h>#include <linux/slab.h>#include <linux/user_namespace.h> /* * Clone a new ns copying an original user ns, setting refcount to 1 * @old_ns: namespace to clone * Return NULL on error (failure to kmalloc), new ns otherwise */static struct user_namespace *clone_user_ns(struct user_namespace *old_ns){	struct user_namespace *ns;	struct user_struct *new_user;	int n; 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);	if (!ns)		return ERR_PTR(-ENOMEM); 	kref_init(&ns->kref); 	for (n = 0; n < UIDHASH_SZ; ++n)		INIT_HLIST_HEAD(ns->uidhash_table + n); 	/* Insert new root user.  */	ns->root_user = alloc_uid(ns, 0);	if (!ns->root_user) {		kfree(ns);		return ERR_PTR(-ENOMEM);	} 	/* Reset current->user with a new one */	new_user = alloc_uid(ns, current->uid);	if (!new_user) {		free_uid(ns->root_user);		kfree(ns);		return ERR_PTR(-ENOMEM);	} 	switch_uid(new_user);	return ns;} struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns){	struct user_namespace *new_ns; 	BUG_ON(!old_ns);	get_user_ns(old_ns); 	if (!(flags & CLONE_NEWUSER))		return old_ns; 	new_ns = clone_user_ns(old_ns); 	put_user_ns(old_ns);	return new_ns;} void free_user_ns(struct kref *kref){	struct user_namespace *ns; 	ns = container_of(kref, struct user_namespace, kref);	release_uids(ns);	kfree(ns);}EXPORT_SYMBOL(free_user_ns);