1 /* 2 * This program is free software; you can redistribute it and/or 3 * modify it under the terms of the GNU General Public License as 4 * published by the Free Software Foundation, version 2 of the 5 * License. 6 */ 7 8 #include <linux/module.h> 9 #include <linux/nsproxy.h> 10 #include <linux/slab.h> 11 #include <linux/user_namespace.h> 12 #include <linux/cred.h> 13 14 /* 15 * Create a new user namespace, deriving the creator from the user in the 16 * passed credentials, and replacing that user with the new root user for the 17 * new namespace. 18 * 19 * This is called by copy_creds(), which will finish setting the target task's 20 * credentials. 21 */ 22 int create_user_ns(struct cred *new) 23 { 24 struct user_namespace *ns; 25 struct user_struct *root_user; 26 int n; 27 28 ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL); 29 if (!ns) 30 return -ENOMEM; 31 32 kref_init(&ns->kref); 33 34 for (n = 0; n < UIDHASH_SZ; ++n) 35 INIT_HLIST_HEAD(ns->uidhash_table + n); 36 37 /* Alloc new root user. */ 38 root_user = alloc_uid(ns, 0); 39 if (!root_user) { 40 kfree(ns); 41 return -ENOMEM; 42 } 43 44 /* set the new root user in the credentials under preparation */ 45 ns->creator = new->user; 46 new->user = root_user; 47 new->uid = new->euid = new->suid = new->fsuid = 0; 48 new->gid = new->egid = new->sgid = new->fsgid = 0; 49 put_group_info(new->group_info); 50 new->group_info = get_group_info(&init_groups); 51 #ifdef CONFIG_KEYS 52 key_put(new->request_key_auth); 53 new->request_key_auth = NULL; 54 #endif 55 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */ 56 57 /* alloc_uid() incremented the userns refcount. Just set it to 1 */ 58 kref_set(&ns->kref, 1); 59 60 return 0; 61 } 62 63 /* 64 * Deferred destructor for a user namespace. This is required because 65 * free_user_ns() may be called with uidhash_lock held, but we need to call 66 * back to free_uid() which will want to take the lock again. 67 */ 68 static void free_user_ns_work(struct work_struct *work) 69 { 70 struct user_namespace *ns = 71 container_of(work, struct user_namespace, destroyer); 72 free_uid(ns->creator); 73 kfree(ns); 74 } 75 76 void free_user_ns(struct kref *kref) 77 { 78 struct user_namespace *ns = 79 container_of(kref, struct user_namespace, kref); 80 81 INIT_WORK(&ns->destroyer, free_user_ns_work); 82 schedule_work(&ns->destroyer); 83 } 84 EXPORT_SYMBOL(free_user_ns); 85