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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