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/version.h> 10 #include <linux/nsproxy.h> 11 #include <linux/user_namespace.h> 12 13 struct user_namespace init_user_ns = { 14 .kref = { 15 .refcount = ATOMIC_INIT(2), 16 }, 17 .root_user = &root_user, 18 }; 19 20 EXPORT_SYMBOL_GPL(init_user_ns); 21 22 #ifdef CONFIG_USER_NS 23 24 /* 25 * Clone a new ns copying an original user ns, setting refcount to 1 26 * @old_ns: namespace to clone 27 * Return NULL on error (failure to kmalloc), new ns otherwise 28 */ 29 static struct user_namespace *clone_user_ns(struct user_namespace *old_ns) 30 { 31 struct user_namespace *ns; 32 struct user_struct *new_user; 33 int n; 34 35 ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL); 36 if (!ns) 37 return ERR_PTR(-ENOMEM); 38 39 kref_init(&ns->kref); 40 41 for (n = 0; n < UIDHASH_SZ; ++n) 42 INIT_LIST_HEAD(ns->uidhash_table + n); 43 44 /* Insert new root user. */ 45 ns->root_user = alloc_uid(ns, 0); 46 if (!ns->root_user) { 47 kfree(ns); 48 return ERR_PTR(-ENOMEM); 49 } 50 51 /* Reset current->user with a new one */ 52 new_user = alloc_uid(ns, current->uid); 53 if (!new_user) { 54 free_uid(ns->root_user); 55 kfree(ns); 56 return ERR_PTR(-ENOMEM); 57 } 58 59 switch_uid(new_user); 60 return ns; 61 } 62 63 struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns) 64 { 65 struct user_namespace *new_ns; 66 67 BUG_ON(!old_ns); 68 get_user_ns(old_ns); 69 70 if (!(flags & CLONE_NEWUSER)) 71 return old_ns; 72 73 new_ns = clone_user_ns(old_ns); 74 75 put_user_ns(old_ns); 76 return new_ns; 77 } 78 79 void free_user_ns(struct kref *kref) 80 { 81 struct user_namespace *ns; 82 83 ns = container_of(kref, struct user_namespace, kref); 84 kfree(ns); 85 } 86 87 #endif /* CONFIG_USER_NS */ 88