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/cred.h>
13
14 /*
15 * Create a new user namespace, deriving the creator from the user in the
16 * passed credentials, and replacing that user with the new root user for the
17 * new namespace.
18 *
19 * This is called by copy_creds(), which will finish setting the target task's
20 * credentials.
21 */
create_user_ns(struct cred * new)22 int create_user_ns(struct cred *new)
23 {
24 struct user_namespace *ns;
25 struct user_struct *root_user;
26 int n;
27
28 ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
29 if (!ns)
30 return -ENOMEM;
31
32 kref_init(&ns->kref);
33
34 for (n = 0; n < UIDHASH_SZ; ++n)
35 INIT_HLIST_HEAD(ns->uidhash_table + n);
36
37 /* Alloc new root user. */
38 root_user = alloc_uid(ns, 0);
39 if (!root_user) {
40 kfree(ns);
41 return -ENOMEM;
42 }
43
44 /* set the new root user in the credentials under preparation */
45 ns->creator = new->user;
46 new->user = root_user;
47 new->uid = new->euid = new->suid = new->fsuid = 0;
48 new->gid = new->egid = new->sgid = new->fsgid = 0;
49 put_group_info(new->group_info);
50 new->group_info = get_group_info(&init_groups);
51 #ifdef CONFIG_KEYS
52 key_put(new->request_key_auth);
53 new->request_key_auth = NULL;
54 #endif
55 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
56
57 /* alloc_uid() incremented the userns refcount. Just set it to 1 */
58 kref_set(&ns->kref, 1);
59
60 return 0;
61 }
62
63 /*
64 * Deferred destructor for a user namespace. This is required because
65 * free_user_ns() may be called with uidhash_lock held, but we need to call
66 * back to free_uid() which will want to take the lock again.
67 */
free_user_ns_work(struct work_struct * work)68 static void free_user_ns_work(struct work_struct *work)
69 {
70 struct user_namespace *ns =
71 container_of(work, struct user_namespace, destroyer);
72 free_uid(ns->creator);
73 kfree(ns);
74 }
75
free_user_ns(struct kref * kref)76 void free_user_ns(struct kref *kref)
77 {
78 struct user_namespace *ns =
79 container_of(kref, struct user_namespace, kref);
80
81 INIT_WORK(&ns->destroyer, free_user_ns_work);
82 schedule_work(&ns->destroyer);
83 }
84 EXPORT_SYMBOL(free_user_ns);
85