Root/kernel/utsname.c

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_fs.h>
19
20static struct uts_namespace *create_uts_ns(void)
21{
22    struct uts_namespace *uts_ns;
23
24    uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
25    if (uts_ns)
26        kref_init(&uts_ns->kref);
27    return uts_ns;
28}
29
30/*
31 * Clone a new ns copying an original utsname, setting refcount to 1
32 * @old_ns: namespace to clone
33 * Return NULL on error (failure to kmalloc), new ns otherwise
34 */
35static struct uts_namespace *clone_uts_ns(struct task_struct *tsk,
36                      struct uts_namespace *old_ns)
37{
38    struct uts_namespace *ns;
39
40    ns = create_uts_ns();
41    if (!ns)
42        return ERR_PTR(-ENOMEM);
43
44    down_read(&uts_sem);
45    memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
46    ns->user_ns = get_user_ns(task_cred_xxx(tsk, user_ns));
47    up_read(&uts_sem);
48    return ns;
49}
50
51/*
52 * Copy task tsk's utsname namespace, or clone it if flags
53 * specifies CLONE_NEWUTS. In latter case, changes to the
54 * utsname of this process won't be seen by parent, and vice
55 * versa.
56 */
57struct uts_namespace *copy_utsname(unsigned long flags,
58                   struct task_struct *tsk)
59{
60    struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
61    struct uts_namespace *new_ns;
62
63    BUG_ON(!old_ns);
64    get_uts_ns(old_ns);
65
66    if (!(flags & CLONE_NEWUTS))
67        return old_ns;
68
69    new_ns = clone_uts_ns(tsk, old_ns);
70
71    put_uts_ns(old_ns);
72    return new_ns;
73}
74
75void free_uts_ns(struct kref *kref)
76{
77    struct uts_namespace *ns;
78
79    ns = container_of(kref, struct uts_namespace, kref);
80    put_user_ns(ns->user_ns);
81    kfree(ns);
82}
83
84static void *utsns_get(struct task_struct *task)
85{
86    struct uts_namespace *ns = NULL;
87    struct nsproxy *nsproxy;
88
89    rcu_read_lock();
90    nsproxy = task_nsproxy(task);
91    if (nsproxy) {
92        ns = nsproxy->uts_ns;
93        get_uts_ns(ns);
94    }
95    rcu_read_unlock();
96
97    return ns;
98}
99
100static void utsns_put(void *ns)
101{
102    put_uts_ns(ns);
103}
104
105static int utsns_install(struct nsproxy *nsproxy, void *ns)
106{
107    get_uts_ns(ns);
108    put_uts_ns(nsproxy->uts_ns);
109    nsproxy->uts_ns = ns;
110    return 0;
111}
112
113const struct proc_ns_operations utsns_operations = {
114    .name = "uts",
115    .type = CLONE_NEWUTS,
116    .get = utsns_get,
117    .put = utsns_put,
118    .install = utsns_install,
119};
120
121

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