linux/kernel/utsname.c
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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_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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