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