/* *  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/export.h>#include <linux/nsproxy.h>#include <linux/slab.h>#include <linux/user_namespace.h>#include <linux/highuid.h>#include <linux/cred.h> static struct kmem_cache *user_ns_cachep __read_mostly; /* * 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 = kmem_cache_alloc(user_ns_cachep, 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) {		kmem_cache_free(user_ns_cachep, 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 */ 	/* root_user holds a reference to ns, our reference can be dropped */	put_user_ns(ns); 	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);	kmem_cache_free(user_ns_cachep, 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); uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid){	struct user_namespace *tmp; 	if (likely(to == cred->user->user_ns))		return uid;  	/* Is cred->user the creator of the target user_ns	 * or the creator of one of it's parents?	 */	for ( tmp = to; tmp != &init_user_ns;	      tmp = tmp->creator->user_ns ) {		if (cred->user == tmp->creator) {			return (uid_t)0;		}	} 	/* No useful relationship so no mapping */	return overflowuid;} gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid){	struct user_namespace *tmp; 	if (likely(to == cred->user->user_ns))		return gid; 	/* Is cred->user the creator of the target user_ns	 * or the creator of one of it's parents?	 */	for ( tmp = to; tmp != &init_user_ns;	      tmp = tmp->creator->user_ns ) {		if (cred->user == tmp->creator) {			return (gid_t)0;		}	} 	/* No useful relationship so no mapping */	return overflowgid;} static __init int user_namespaces_init(void){	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);	return 0;}module_init(user_namespaces_init);