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
19 static struct kmem_cache *uts_ns_cache __ro_after_init;
20
inc_uts_namespaces(struct user_namespace * ns)21 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
22 {
23 return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
24 }
25
dec_uts_namespaces(struct ucounts * ucounts)26 static 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 */
clone_uts_ns(struct user_namespace * user_ns,struct uts_namespace * old_ns)36 static 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
65 fail_free:
66 kmem_cache_free(uts_ns_cache, ns);
67 fail_dec:
68 dec_uts_namespaces(ucounts);
69 fail:
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 */
copy_utsname(u64 flags,struct user_namespace * user_ns,struct uts_namespace * old_ns)79 struct 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
free_uts_ns(struct uts_namespace * ns)95 void 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
utsns_get(struct task_struct * task)105 static 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
utsns_put(struct ns_common * ns)121 static void utsns_put(struct ns_common *ns)
122 {
123 put_uts_ns(to_uts_ns(ns));
124 }
125
utsns_install(struct nsset * nsset,struct ns_common * new)126 static 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
utsns_owner(struct ns_common * ns)141 static struct user_namespace *utsns_owner(struct ns_common *ns)
142 {
143 return to_uts_ns(ns)->user_ns;
144 }
145
146 const 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
uts_ns_init(void)154 void __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 }
164