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