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/highuid.h> 13 #include <linux/cred.h> 14 15 static struct kmem_cache *user_ns_cachep __read_mostly; 16 17 /* 18 * Create a new user namespace, deriving the creator from the user in the 19 * passed credentials, and replacing that user with the new root user for the 20 * new namespace. 21 * 22 * This is called by copy_creds(), which will finish setting the target task's 23 * credentials. 24 */ 25 int create_user_ns(struct cred *new) 26 { 27 struct user_namespace *ns; 28 struct user_struct *root_user; 29 int n; 30 31 ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL); 32 if (!ns) 33 return -ENOMEM; 34 35 kref_init(&ns->kref); 36 37 for (n = 0; n < UIDHASH_SZ; ++n) 38 INIT_HLIST_HEAD(ns->uidhash_table + n); 39 40 /* Alloc new root user. */ 41 root_user = alloc_uid(ns, 0); 42 if (!root_user) { 43 kmem_cache_free(user_ns_cachep, ns); 44 return -ENOMEM; 45 } 46 47 /* set the new root user in the credentials under preparation */ 48 ns->creator = new->user; 49 new->user = root_user; 50 new->uid = new->euid = new->suid = new->fsuid = 0; 51 new->gid = new->egid = new->sgid = new->fsgid = 0; 52 put_group_info(new->group_info); 53 new->group_info = get_group_info(&init_groups); 54 #ifdef CONFIG_KEYS 55 key_put(new->request_key_auth); 56 new->request_key_auth = NULL; 57 #endif 58 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */ 59 60 /* root_user holds a reference to ns, our reference can be dropped */ 61 put_user_ns(ns); 62 63 return 0; 64 } 65 66 /* 67 * Deferred destructor for a user namespace. This is required because 68 * free_user_ns() may be called with uidhash_lock held, but we need to call 69 * back to free_uid() which will want to take the lock again. 70 */ 71 static void free_user_ns_work(struct work_struct *work) 72 { 73 struct user_namespace *ns = 74 container_of(work, struct user_namespace, destroyer); 75 free_uid(ns->creator); 76 kmem_cache_free(user_ns_cachep, ns); 77 } 78 79 void free_user_ns(struct kref *kref) 80 { 81 struct user_namespace *ns = 82 container_of(kref, struct user_namespace, kref); 83 84 INIT_WORK(&ns->destroyer, free_user_ns_work); 85 schedule_work(&ns->destroyer); 86 } 87 EXPORT_SYMBOL(free_user_ns); 88 89 uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid) 90 { 91 struct user_namespace *tmp; 92 93 if (likely(to == cred->user->user_ns)) 94 return uid; 95 96 97 /* Is cred->user the creator of the target user_ns 98 * or the creator of one of it's parents? 99 */ 100 for ( tmp = to; tmp != &init_user_ns; 101 tmp = tmp->creator->user_ns ) { 102 if (cred->user == tmp->creator) { 103 return (uid_t)0; 104 } 105 } 106 107 /* No useful relationship so no mapping */ 108 return overflowuid; 109 } 110 111 gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid) 112 { 113 struct user_namespace *tmp; 114 115 if (likely(to == cred->user->user_ns)) 116 return gid; 117 118 /* Is cred->user the creator of the target user_ns 119 * or the creator of one of it's parents? 120 */ 121 for ( tmp = to; tmp != &init_user_ns; 122 tmp = tmp->creator->user_ns ) { 123 if (cred->user == tmp->creator) { 124 return (gid_t)0; 125 } 126 } 127 128 /* No useful relationship so no mapping */ 129 return overflowgid; 130 } 131 132 static __init int user_namespaces_init(void) 133 { 134 user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC); 135 return 0; 136 } 137 module_init(user_namespaces_init); 138