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_ns.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 ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
34 */
35static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
36                      struct uts_namespace *old_ns)
37{
38    struct uts_namespace *ns;
39    int err;
40
41    ns = create_uts_ns();
42    if (!ns)
43        return ERR_PTR(-ENOMEM);
44
45    err = proc_alloc_inum(&ns->proc_inum);
46    if (err) {
47        kfree(ns);
48        return ERR_PTR(err);
49    }
50
51    down_read(&uts_sem);
52    memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
53    ns->user_ns = get_user_ns(user_ns);
54    up_read(&uts_sem);
55    return ns;
56}
57
58/*
59 * Copy task tsk's utsname namespace, or clone it if flags
60 * specifies CLONE_NEWUTS. In latter case, changes to the
61 * utsname of this process won't be seen by parent, and vice
62 * versa.
63 */
64struct uts_namespace *copy_utsname(unsigned long flags,
65    struct user_namespace *user_ns, struct uts_namespace *old_ns)
66{
67    struct uts_namespace *new_ns;
68
69    BUG_ON(!old_ns);
70    get_uts_ns(old_ns);
71
72    if (!(flags & CLONE_NEWUTS))
73        return old_ns;
74
75    new_ns = clone_uts_ns(user_ns, old_ns);
76
77    put_uts_ns(old_ns);
78    return new_ns;
79}
80
81void free_uts_ns(struct kref *kref)
82{
83    struct uts_namespace *ns;
84
85    ns = container_of(kref, struct uts_namespace, kref);
86    put_user_ns(ns->user_ns);
87    proc_free_inum(ns->proc_inum);
88    kfree(ns);
89}
90
91static void *utsns_get(struct task_struct *task)
92{
93    struct uts_namespace *ns = NULL;
94    struct nsproxy *nsproxy;
95
96    rcu_read_lock();
97    nsproxy = task_nsproxy(task);
98    if (nsproxy) {
99        ns = nsproxy->uts_ns;
100        get_uts_ns(ns);
101    }
102    rcu_read_unlock();
103
104    return ns;
105}
106
107static void utsns_put(void *ns)
108{
109    put_uts_ns(ns);
110}
111
112static int utsns_install(struct nsproxy *nsproxy, void *new)
113{
114    struct uts_namespace *ns = new;
115
116    if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
117        !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
118        return -EPERM;
119
120    get_uts_ns(ns);
121    put_uts_ns(nsproxy->uts_ns);
122    nsproxy->uts_ns = ns;
123    return 0;
124}
125
126static unsigned int utsns_inum(void *vp)
127{
128    struct uts_namespace *ns = vp;
129
130    return ns->proc_inum;
131}
132
133const struct proc_ns_operations utsns_operations = {
134    .name = "uts",
135    .type = CLONE_NEWUTS,
136    .get = utsns_get,
137    .put = utsns_put,
138    .install = utsns_install,
139    .inum = utsns_inum,
140};
141

Archive Download this file



interactive