projects/linux·blob 2c455ddc · refs

163 lines · 3.5 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2004 IBM Corporation
4 *
5 * Author: Serge Hallyn <[email protected]>
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(), UCOUNT_UTS_NAMESPACES);
24}
25
26static void dec_uts_namespaces(struct ucounts *ucounts)
27{
28 dec_ucount(ucounts, 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(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(&uts_sem);
59 memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
60 ns->user_ns = get_user_ns(user_ns);
61 up_read(&uts_sem);
62 ns_tree_add(ns);
63 return ns;
64
65fail_free:
66 kmem_cache_free(uts_ns_cache, ns);
67fail_dec:
68 dec_uts_namespaces(ucounts);
69fail:
70 return ERR_PTR(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 get_uts_ns(old_ns);
85
86 if (!(flags & CLONE_NEWUTS))
87 return old_ns;
88
89 new_ns = clone_uts_ns(user_ns, old_ns);
90
91 put_uts_ns(old_ns);
92 return new_ns;
93}
94
95void free_uts_ns(struct uts_namespace *ns)
96{
97 ns_tree_remove(ns);
98 dec_uts_namespaces(ns->ucounts);
99 put_user_ns(ns->user_ns);
100 ns_common_free(ns);
101 /* Concurrent nstree traversal depends on a grace period. */
102 kfree_rcu(ns, ns.ns_rcu);
103}
104
105static struct ns_common *utsns_get(struct task_struct *task)
106{
107 struct uts_namespace *ns = NULL;
108 struct nsproxy *nsproxy;
109
110 task_lock(task);
111 nsproxy = task->nsproxy;
112 if (nsproxy) {
113 ns = nsproxy->uts_ns;
114 get_uts_ns(ns);
115 }
116 task_unlock(task);
117
118 return ns ? &ns->ns : NULL;
119}
120
121static void utsns_put(struct ns_common *ns)
122{
123 put_uts_ns(to_uts_ns(ns));
124}
125
126static int utsns_install(struct nsset *nsset, struct ns_common *new)
127{
128 struct nsproxy *nsproxy = nsset->nsproxy;
129 struct uts_namespace *ns = to_uts_ns(new);
130
131 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
132 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
133 return -EPERM;
134
135 get_uts_ns(ns);
136 put_uts_ns(nsproxy->uts_ns);
137 nsproxy->uts_ns = ns;
138 return 0;
139}
140
141static struct user_namespace *utsns_owner(struct ns_common *ns)
142{
143 return to_uts_ns(ns)->user_ns;
144}
145
146const struct proc_ns_operations utsns_operations = {
147 .name = "uts",
148 .get = utsns_get,
149 .put = utsns_put,
150 .install = utsns_install,
151 .owner = utsns_owner,
152};
153
154void __init uts_ns_init(void)
155{
156 uts_ns_cache = kmem_cache_create_usercopy(
157 "uts_namespace", sizeof(struct uts_namespace), 0,
158 SLAB_PANIC|SLAB_ACCOUNT,
159 offsetof(struct uts_namespace, name),
160 sizeof_field(struct uts_namespace, name),
161 NULL);
162 ns_tree_add(&init_uts_ns);
163}