/* *  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/nsproxy.h>#include <linux/slab.h>#include <linux/user_namespace.h>#include <linux/cred.h> /* * Create a new user namespace, deriving the creator from the user in the * passed credentials, and replacing that user with the new root user for the * new namespace. * * This is called by copy_creds(), which will finish setting the target task's * credentials. */int create_user_ns(struct cred *new){	struct user_namespace *ns;	struct user_struct *root_user;	int n; 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);	if (!ns)		return -ENOMEM; 	kref_init(&ns->kref); 	for (n = 0; n < UIDHASH_SZ; ++n)		INIT_HLIST_HEAD(ns->uidhash_table + n); 	/* Alloc new root user.  */	root_user = alloc_uid(ns, 0);	if (!root_user) {		kfree(ns);		return -ENOMEM;	} 	/* set the new root user in the credentials under preparation */	ns->creator = new->user;	new->user = root_user;	new->uid = new->euid = new->suid = new->fsuid = 0;	new->gid = new->egid = new->sgid = new->fsgid = 0;	put_group_info(new->group_info);	new->group_info = get_group_info(&init_groups);#ifdef CONFIG_KEYS	key_put(new->request_key_auth);	new->request_key_auth = NULL;#endif	/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */ 	/* alloc_uid() incremented the userns refcount.  Just set it to 1 */	kref_set(&ns->kref, 1); 	return 0;} /* * Deferred destructor for a user namespace.  This is required because * free_user_ns() may be called with uidhash_lock held, but we need to call * back to free_uid() which will want to take the lock again. */static void free_user_ns_work(struct work_struct *work){	struct user_namespace *ns =		container_of(work, struct user_namespace, destroyer);	free_uid(ns->creator);	kfree(ns);} void free_user_ns(struct kref *kref){	struct user_namespace *ns =		container_of(kref, struct user_namespace, kref); 	INIT_WORK(&ns->destroyer, free_user_ns_work);	schedule_work(&ns->destroyer);}EXPORT_SYMBOL(free_user_ns);