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/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
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