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/cred.h>
18 #include <linux/user_namespace.h>
19 #include <linux/proc_ns.h>
20 #include <linux/sched/task.h>
21
22 static struct kmem_cache *uts_ns_cache __ro_after_init;
23
inc_uts_namespaces(struct user_namespace * ns)24 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
25 {
26 return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
27 }
28
dec_uts_namespaces(struct ucounts * ucounts)29 static void dec_uts_namespaces(struct ucounts *ucounts)
30 {
31 dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
32 }
33
create_uts_ns(void)34 static struct uts_namespace *create_uts_ns(void)
35 {
36 struct uts_namespace *uts_ns;
37
38 uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
39 if (uts_ns)
40 kref_init(&uts_ns->kref);
41 return uts_ns;
42 }
43
44 /*
45 * Clone a new ns copying an original utsname, setting refcount to 1
46 * @old_ns: namespace to clone
47 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
48 */
clone_uts_ns(struct user_namespace * user_ns,struct uts_namespace * old_ns)49 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
50 struct uts_namespace *old_ns)
51 {
52 struct uts_namespace *ns;
53 struct ucounts *ucounts;
54 int err;
55
56 err = -ENOSPC;
57 ucounts = inc_uts_namespaces(user_ns);
58 if (!ucounts)
59 goto fail;
60
61 err = -ENOMEM;
62 ns = create_uts_ns();
63 if (!ns)
64 goto fail_dec;
65
66 err = ns_alloc_inum(&ns->ns);
67 if (err)
68 goto fail_free;
69
70 ns->ucounts = ucounts;
71 ns->ns.ops = &utsns_operations;
72
73 down_read(&uts_sem);
74 memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
75 ns->user_ns = get_user_ns(user_ns);
76 up_read(&uts_sem);
77 return ns;
78
79 fail_free:
80 kmem_cache_free(uts_ns_cache, ns);
81 fail_dec:
82 dec_uts_namespaces(ucounts);
83 fail:
84 return ERR_PTR(err);
85 }
86
87 /*
88 * Copy task tsk's utsname namespace, or clone it if flags
89 * specifies CLONE_NEWUTS. In latter case, changes to the
90 * utsname of this process won't be seen by parent, and vice
91 * versa.
92 */
copy_utsname(unsigned long flags,struct user_namespace * user_ns,struct uts_namespace * old_ns)93 struct uts_namespace *copy_utsname(unsigned long flags,
94 struct user_namespace *user_ns, struct uts_namespace *old_ns)
95 {
96 struct uts_namespace *new_ns;
97
98 BUG_ON(!old_ns);
99 get_uts_ns(old_ns);
100
101 if (!(flags & CLONE_NEWUTS))
102 return old_ns;
103
104 new_ns = clone_uts_ns(user_ns, old_ns);
105
106 put_uts_ns(old_ns);
107 return new_ns;
108 }
109
free_uts_ns(struct kref * kref)110 void free_uts_ns(struct kref *kref)
111 {
112 struct uts_namespace *ns;
113
114 ns = container_of(kref, struct uts_namespace, kref);
115 dec_uts_namespaces(ns->ucounts);
116 put_user_ns(ns->user_ns);
117 ns_free_inum(&ns->ns);
118 kmem_cache_free(uts_ns_cache, ns);
119 }
120
to_uts_ns(struct ns_common * ns)121 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
122 {
123 return container_of(ns, struct uts_namespace, ns);
124 }
125
utsns_get(struct task_struct * task)126 static struct ns_common *utsns_get(struct task_struct *task)
127 {
128 struct uts_namespace *ns = NULL;
129 struct nsproxy *nsproxy;
130
131 task_lock(task);
132 nsproxy = task->nsproxy;
133 if (nsproxy) {
134 ns = nsproxy->uts_ns;
135 get_uts_ns(ns);
136 }
137 task_unlock(task);
138
139 return ns ? &ns->ns : NULL;
140 }
141
utsns_put(struct ns_common * ns)142 static void utsns_put(struct ns_common *ns)
143 {
144 put_uts_ns(to_uts_ns(ns));
145 }
146
utsns_install(struct nsproxy * nsproxy,struct ns_common * new)147 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
148 {
149 struct uts_namespace *ns = to_uts_ns(new);
150
151 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
152 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
153 return -EPERM;
154
155 get_uts_ns(ns);
156 put_uts_ns(nsproxy->uts_ns);
157 nsproxy->uts_ns = ns;
158 return 0;
159 }
160
utsns_owner(struct ns_common * ns)161 static struct user_namespace *utsns_owner(struct ns_common *ns)
162 {
163 return to_uts_ns(ns)->user_ns;
164 }
165
166 const struct proc_ns_operations utsns_operations = {
167 .name = "uts",
168 .type = CLONE_NEWUTS,
169 .get = utsns_get,
170 .put = utsns_put,
171 .install = utsns_install,
172 .owner = utsns_owner,
173 };
174
uts_ns_init(void)175 void __init uts_ns_init(void)
176 {
177 uts_ns_cache = kmem_cache_create_usercopy(
178 "uts_namespace", sizeof(struct uts_namespace), 0,
179 SLAB_PANIC|SLAB_ACCOUNT,
180 offsetof(struct uts_namespace, name),
181 sizeof_field(struct uts_namespace, name),
182 NULL);
183 }
184
