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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/user_namespace.h> | |
18 | #include <linux/proc_ns.h> | |
19 | ||
20 | static struct ucounts *inc_uts_namespaces(struct user_namespace *ns) | |
21 | { | |
22 | return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES); | |
23 | } | |
24 | ||
25 | static void dec_uts_namespaces(struct ucounts *ucounts) | |
26 | { | |
27 | dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES); | |
28 | } | |
29 | ||
30 | static struct uts_namespace *create_uts_ns(void) | |
31 | { | |
32 | struct uts_namespace *uts_ns; | |
33 | ||
34 | uts_ns = kmalloc(sizeof(struct uts_namespace), 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 kmalloc), new ns otherwise | |
44 | */ | |
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 | kfree(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 | */ | |
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 | ||
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 | kfree(ns); | |
115 | } | |
116 | ||
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 | ||
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 | ||
138 | static void utsns_put(struct ns_common *ns) | |
139 | { | |
140 | put_uts_ns(to_uts_ns(ns)); | |
141 | } | |
142 | ||
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 | ||
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 | }; |