1/*
2 *  Copyright (C) 2004 IBM Corporation
3 *
4 *  Author: Serge Hallyn <serue@us.ibm.com>
5 *
6 *  This program is free software; you can redistribute it and/or
7 *  modify it under the terms of the GNU General Public License as
8 *  published by the Free Software Foundation, version 2 of the
9 *  License.
10 */
11
12#include <linux/export.h>
13#include <linux/uts.h>
14#include <linux/utsname.h>
15#include <linux/err.h>
16#include <linux/slab.h>
17#include <linux/user_namespace.h>
18#include <linux/proc_ns.h>
19
20static struct uts_namespace *create_uts_ns(void)
21{
22	struct uts_namespace *uts_ns;
23
24	uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
25	if (uts_ns)
26		kref_init(&uts_ns->kref);
27	return uts_ns;
28}
29
30/*
31 * Clone a new ns copying an original utsname, setting refcount to 1
32 * @old_ns: namespace to clone
33 * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
34 */
35static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
36					  struct uts_namespace *old_ns)
37{
38	struct uts_namespace *ns;
39	int err;
40
41	ns = create_uts_ns();
42	if (!ns)
43		return ERR_PTR(-ENOMEM);
44
45	err = ns_alloc_inum(&ns->ns);
46	if (err) {
47		kfree(ns);
48		return ERR_PTR(err);
49	}
50
51	ns->ns.ops = &utsns_operations;
52
53	down_read(&uts_sem);
54	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
55	ns->user_ns = get_user_ns(user_ns);
56	up_read(&uts_sem);
57	return ns;
58}
59
60/*
61 * Copy task tsk's utsname namespace, or clone it if flags
62 * specifies CLONE_NEWUTS.  In latter case, changes to the
63 * utsname of this process won't be seen by parent, and vice
64 * versa.
65 */
66struct uts_namespace *copy_utsname(unsigned long flags,
67	struct user_namespace *user_ns, struct uts_namespace *old_ns)
68{
69	struct uts_namespace *new_ns;
70
71	BUG_ON(!old_ns);
72	get_uts_ns(old_ns);
73
74	if (!(flags & CLONE_NEWUTS))
75		return old_ns;
76
77	new_ns = clone_uts_ns(user_ns, old_ns);
78
79	put_uts_ns(old_ns);
80	return new_ns;
81}
82
83void free_uts_ns(struct kref *kref)
84{
85	struct uts_namespace *ns;
86
87	ns = container_of(kref, struct uts_namespace, kref);
88	put_user_ns(ns->user_ns);
89	ns_free_inum(&ns->ns);
90	kfree(ns);
91}
92
93static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
94{
95	return container_of(ns, struct uts_namespace, ns);
96}
97
98static struct ns_common *utsns_get(struct task_struct *task)
99{
100	struct uts_namespace *ns = NULL;
101	struct nsproxy *nsproxy;
102
103	task_lock(task);
104	nsproxy = task->nsproxy;
105	if (nsproxy) {
106		ns = nsproxy->uts_ns;
107		get_uts_ns(ns);
108	}
109	task_unlock(task);
110
111	return ns ? &ns->ns : NULL;
112}
113
114static void utsns_put(struct ns_common *ns)
115{
116	put_uts_ns(to_uts_ns(ns));
117}
118
119static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
120{
121	struct uts_namespace *ns = to_uts_ns(new);
122
123	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
124	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
125		return -EPERM;
126
127	get_uts_ns(ns);
128	put_uts_ns(nsproxy->uts_ns);
129	nsproxy->uts_ns = ns;
130	return 0;
131}
132
133const struct proc_ns_operations utsns_operations = {
134	.name		= "uts",
135	.type		= CLONE_NEWUTS,
136	.get		= utsns_get,
137	.put		= utsns_put,
138	.install	= utsns_install,
139};
140