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/*
* Copyright (C) 2004 IBM Corporation
*
* Author: Serge Hallyn <serue@us.ibm.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*/

#include <linux/module.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/user_namespace.h>
#include <linux/proc_fs.h>

static struct uts_namespace *create_uts_ns(void)
{
struct uts_namespace *uts_ns;

uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
if (uts_ns)
kref_init(&uts_ns->kref);
return uts_ns;
}

/*
* Clone a new ns copying an original utsname, setting refcount to 1
* @old_ns: namespace to clone
* Return NULL on error (failure to kmalloc), new ns otherwise
*/
static struct uts_namespace *clone_uts_ns(struct task_struct *tsk,
struct uts_namespace *old_ns)
{
struct uts_namespace *ns;

ns = create_uts_ns();
if (!ns)
return ERR_PTR(-ENOMEM);

down_read(&uts_sem);
memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns);
up_read(&uts_sem);
return ns;
}

/*
* Copy task tsk's utsname namespace, or clone it if flags
* specifies CLONE_NEWUTS. In latter case, changes to the
* utsname of this process won't be seen by parent, and vice
* versa.
*/
struct uts_namespace *copy_utsname(unsigned long flags,
struct task_struct *tsk)
{
struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
struct uts_namespace *new_ns;

BUG_ON(!old_ns);
get_uts_ns(old_ns);

if (!(flags & CLONE_NEWUTS))
return old_ns;

new_ns = clone_uts_ns(tsk, old_ns);

put_uts_ns(old_ns);
return new_ns;
}

void free_uts_ns(struct kref *kref)
{
struct uts_namespace *ns;

ns = container_of(kref, struct uts_namespace, kref);
put_user_ns(ns->user_ns);
kfree(ns);
}

static void *utsns_get(struct task_struct *task)
{
struct uts_namespace *ns = NULL;
struct nsproxy *nsproxy;

rcu_read_lock();
nsproxy = task_nsproxy(task);
if (nsproxy) {
ns = nsproxy->uts_ns;
get_uts_ns(ns);
}
rcu_read_unlock();

return ns;
}

static void utsns_put(void *ns)
{
put_uts_ns(ns);
}

static int utsns_install(struct nsproxy *nsproxy, void *ns)
{
get_uts_ns(ns);
put_uts_ns(nsproxy->uts_ns);
nsproxy->uts_ns = ns;
return 0;
}

const struct proc_ns_operations utsns_operations = {
.name = "uts",
.type = CLONE_NEWUTS,
.get = utsns_get,
.put = utsns_put,
.install = utsns_install,
};
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