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