1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2004 IBM Corporation
4 *
5 * Author: Serge Hallyn <serue@us.ibm.com>
6 */
7
8#include <linux/export.h>
9#include <linux/uts.h>
10#include <linux/utsname.h>
11#include <linux/err.h>
12#include <linux/slab.h>
13#include <linux/cred.h>
14#include <linux/user_namespace.h>
15#include <linux/proc_ns.h>
16#include <linux/nstree.h>
17#include <linux/sched/task.h>
18
19static struct kmem_cache *uts_ns_cache __ro_after_init;
20
21static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
22{
23 return inc_ucount(ns, current_euid(), type: UCOUNT_UTS_NAMESPACES);
24}
25
26static void dec_uts_namespaces(struct ucounts *ucounts)
27{
28 dec_ucount(ucounts, type: UCOUNT_UTS_NAMESPACES);
29}
30
31/*
32 * Clone a new ns copying an original utsname, setting refcount to 1
33 * @old_ns: namespace to clone
34 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
35 */
36static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
37 struct uts_namespace *old_ns)
38{
39 struct uts_namespace *ns;
40 struct ucounts *ucounts;
41 int err;
42
43 err = -ENOSPC;
44 ucounts = inc_uts_namespaces(ns: user_ns);
45 if (!ucounts)
46 goto fail;
47
48 err = -ENOMEM;
49 ns = kmem_cache_zalloc(uts_ns_cache, GFP_KERNEL);
50 if (!ns)
51 goto fail_dec;
52
53 err = ns_common_init(ns);
54 if (err)
55 goto fail_free;
56
57 ns->ucounts = ucounts;
58 down_read(sem: &uts_sem);
59 memcpy(to: &ns->name, from: &old_ns->name, len: sizeof(ns->name));
60 ns->user_ns = get_user_ns(ns: user_ns);
61 up_read(sem: &uts_sem);
62 ns_tree_add(ns);
63 return ns;
64
65fail_free:
66 kmem_cache_free(s: uts_ns_cache, objp: ns);
67fail_dec:
68 dec_uts_namespaces(ucounts);
69fail:
70 return ERR_PTR(error: err);
71}
72
73/*
74 * Copy task tsk's utsname namespace, or clone it if flags
75 * specifies CLONE_NEWUTS. In latter case, changes to the
76 * utsname of this process won't be seen by parent, and vice
77 * versa.
78 */
79struct uts_namespace *copy_utsname(u64 flags,
80 struct user_namespace *user_ns, struct uts_namespace *old_ns)
81{
82 struct uts_namespace *new_ns;
83
84 BUG_ON(!old_ns);
85 get_uts_ns(ns: old_ns);
86
87 if (!(flags & CLONE_NEWUTS))
88 return old_ns;
89
90 new_ns = clone_uts_ns(user_ns, old_ns);
91
92 put_uts_ns(ns: old_ns);
93 return new_ns;
94}
95
96void free_uts_ns(struct uts_namespace *ns)
97{
98 ns_tree_remove(ns);
99 dec_uts_namespaces(ucounts: ns->ucounts);
100 put_user_ns(ns: ns->user_ns);
101 ns_common_free(ns);
102 /* Concurrent nstree traversal depends on a grace period. */
103 kfree_rcu(ns, ns.ns_rcu);
104}
105
106static struct ns_common *utsns_get(struct task_struct *task)
107{
108 struct uts_namespace *ns = NULL;
109 struct nsproxy *nsproxy;
110
111 task_lock(p: task);
112 nsproxy = task->nsproxy;
113 if (nsproxy) {
114 ns = nsproxy->uts_ns;
115 get_uts_ns(ns);
116 }
117 task_unlock(p: task);
118
119 return ns ? &ns->ns : NULL;
120}
121
122static void utsns_put(struct ns_common *ns)
123{
124 put_uts_ns(ns: to_uts_ns(ns));
125}
126
127static int utsns_install(struct nsset *nsset, struct ns_common *new)
128{
129 struct nsproxy *nsproxy = nsset->nsproxy;
130 struct uts_namespace *ns = to_uts_ns(ns: new);
131
132 if (!ns_capable(ns: ns->user_ns, CAP_SYS_ADMIN) ||
133 !ns_capable(ns: nsset->cred->user_ns, CAP_SYS_ADMIN))
134 return -EPERM;
135
136 get_uts_ns(ns);
137 put_uts_ns(ns: nsproxy->uts_ns);
138 nsproxy->uts_ns = ns;
139 return 0;
140}
141
142static struct user_namespace *utsns_owner(struct ns_common *ns)
143{
144 return to_uts_ns(ns)->user_ns;
145}
146
147const struct proc_ns_operations utsns_operations = {
148 .name = "uts",
149 .get = utsns_get,
150 .put = utsns_put,
151 .install = utsns_install,
152 .owner = utsns_owner,
153};
154
155void __init uts_ns_init(void)
156{
157 uts_ns_cache = kmem_cache_create_usercopy(
158 name: "uts_namespace", size: sizeof(struct uts_namespace), align: 0,
159 SLAB_PANIC|SLAB_ACCOUNT,
160 offsetof(struct uts_namespace, name),
161 sizeof_field(struct uts_namespace, name),
162 NULL);
163 ns_tree_add(&init_uts_ns);
164}
165