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/sched/task.h>
17
18 static struct kmem_cache *uts_ns_cache __ro_after_init;
19
inc_uts_namespaces(struct user_namespace * ns)20 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
21 {
22 return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
23 }
24
dec_uts_namespaces(struct ucounts * ucounts)25 static void dec_uts_namespaces(struct ucounts *ucounts)
26 {
27 dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
28 }
29
create_uts_ns(void)30 static struct uts_namespace *create_uts_ns(void)
31 {
32 struct uts_namespace *uts_ns;
33
34 uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
35 if (uts_ns)
36 kref_init(&uts_ns->kref);
37 return uts_ns;
38 }
39
40 /*
41 * Clone a new ns copying an original utsname, setting refcount to 1
42 * @old_ns: namespace to clone
43 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
44 */
clone_uts_ns(struct user_namespace * user_ns,struct uts_namespace * old_ns)45 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
46 struct uts_namespace *old_ns)
47 {
48 struct uts_namespace *ns;
49 struct ucounts *ucounts;
50 int err;
51
52 err = -ENOSPC;
53 ucounts = inc_uts_namespaces(user_ns);
54 if (!ucounts)
55 goto fail;
56
57 err = -ENOMEM;
58 ns = create_uts_ns();
59 if (!ns)
60 goto fail_dec;
61
62 err = ns_alloc_inum(&ns->ns);
63 if (err)
64 goto fail_free;
65
66 ns->ucounts = ucounts;
67 ns->ns.ops = &utsns_operations;
68
69 down_read(&uts_sem);
70 memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
71 ns->user_ns = get_user_ns(user_ns);
72 up_read(&uts_sem);
73 return ns;
74
75 fail_free:
76 kmem_cache_free(uts_ns_cache, ns);
77 fail_dec:
78 dec_uts_namespaces(ucounts);
79 fail:
80 return ERR_PTR(err);
81 }
82
83 /*
84 * Copy task tsk's utsname namespace, or clone it if flags
85 * specifies CLONE_NEWUTS. In latter case, changes to the
86 * utsname of this process won't be seen by parent, and vice
87 * versa.
88 */
copy_utsname(unsigned long flags,struct user_namespace * user_ns,struct uts_namespace * old_ns)89 struct uts_namespace *copy_utsname(unsigned long flags,
90 struct user_namespace *user_ns, struct uts_namespace *old_ns)
91 {
92 struct uts_namespace *new_ns;
93
94 BUG_ON(!old_ns);
95 get_uts_ns(old_ns);
96
97 if (!(flags & CLONE_NEWUTS))
98 return old_ns;
99
100 new_ns = clone_uts_ns(user_ns, old_ns);
101
102 put_uts_ns(old_ns);
103 return new_ns;
104 }
105
free_uts_ns(struct kref * kref)106 void free_uts_ns(struct kref *kref)
107 {
108 struct uts_namespace *ns;
109
110 ns = container_of(kref, struct uts_namespace, kref);
111 dec_uts_namespaces(ns->ucounts);
112 put_user_ns(ns->user_ns);
113 ns_free_inum(&ns->ns);
114 kmem_cache_free(uts_ns_cache, ns);
115 }
116
to_uts_ns(struct ns_common * ns)117 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
118 {
119 return container_of(ns, struct uts_namespace, ns);
120 }
121
utsns_get(struct task_struct * task)122 static struct ns_common *utsns_get(struct task_struct *task)
123 {
124 struct uts_namespace *ns = NULL;
125 struct nsproxy *nsproxy;
126
127 task_lock(task);
128 nsproxy = task->nsproxy;
129 if (nsproxy) {
130 ns = nsproxy->uts_ns;
131 get_uts_ns(ns);
132 }
133 task_unlock(task);
134
135 return ns ? &ns->ns : NULL;
136 }
137
utsns_put(struct ns_common * ns)138 static void utsns_put(struct ns_common *ns)
139 {
140 put_uts_ns(to_uts_ns(ns));
141 }
142
utsns_install(struct nsproxy * nsproxy,struct ns_common * new)143 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
144 {
145 struct uts_namespace *ns = to_uts_ns(new);
146
147 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
148 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
149 return -EPERM;
150
151 get_uts_ns(ns);
152 put_uts_ns(nsproxy->uts_ns);
153 nsproxy->uts_ns = ns;
154 return 0;
155 }
156
utsns_owner(struct ns_common * ns)157 static struct user_namespace *utsns_owner(struct ns_common *ns)
158 {
159 return to_uts_ns(ns)->user_ns;
160 }
161
162 const struct proc_ns_operations utsns_operations = {
163 .name = "uts",
164 .type = CLONE_NEWUTS,
165 .get = utsns_get,
166 .put = utsns_put,
167 .install = utsns_install,
168 .owner = utsns_owner,
169 };
170
uts_ns_init(void)171 void __init uts_ns_init(void)
172 {
173 uts_ns_cache = kmem_cache_create_usercopy(
174 "uts_namespace", sizeof(struct uts_namespace), 0,
175 SLAB_PANIC|SLAB_ACCOUNT,
176 offsetof(struct uts_namespace, name),
177 sizeof_field(struct uts_namespace, name),
178 NULL);
179 }
180