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// SPDX-License-Identifier: GPL-2.0
/*
* Author: Andrei Vagin <avagin@openvz.org>
* Author: Dmitry Safonov <dima@arista.com>
*/
#include <linux/time_namespace.h>
#include <linux/user_namespace.h>
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/proc_ns.h>
#include <linux/export.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/err.h>
#include <linux/mm.h>
static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);
}
static void dec_time_namespaces(struct ucounts *ucounts)
{
dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES);
}
/**
* clone_time_ns - Clone a time namespace
* @user_ns: User namespace which owns a new namespace.
* @old_ns: Namespace to clone
*
* Clone @old_ns and set the clone refcount to 1
*
* Return: The new namespace or ERR_PTR.
*/
static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
struct time_namespace *old_ns)
{
struct time_namespace *ns;
struct ucounts *ucounts;
int err;
err = -ENOSPC;
ucounts = inc_time_namespaces(user_ns);
if (!ucounts)
goto fail;
err = -ENOMEM;
ns = kmalloc(sizeof(*ns), GFP_KERNEL);
if (!ns)
goto fail_dec;
kref_init(&ns->kref);
err = ns_alloc_inum(&ns->ns);
if (err)
goto fail_free;
ns->ucounts = ucounts;
ns->ns.ops = &timens_operations;
ns->user_ns = get_user_ns(user_ns);
ns->offsets = old_ns->offsets;
return ns;
fail_free:
kfree(ns);
fail_dec:
dec_time_namespaces(ucounts);
fail:
return ERR_PTR(err);
}
/**
* copy_time_ns - Create timens_for_children from @old_ns
* @flags: Cloning flags
* @user_ns: User namespace which owns a new namespace.
* @old_ns: Namespace to clone
*
* If CLONE_NEWTIME specified in @flags, creates a new timens_for_children;
* adds a refcounter to @old_ns otherwise.
*
* Return: timens_for_children namespace or ERR_PTR.
*/
struct time_namespace *copy_time_ns(unsigned long flags,
struct user_namespace *user_ns, struct time_namespace *old_ns)
{
if (!(flags & CLONE_NEWTIME))
return get_time_ns(old_ns);
return clone_time_ns(user_ns, old_ns);
}
void free_time_ns(struct kref *kref)
{
struct time_namespace *ns;
ns = container_of(kref, struct time_namespace, kref);
dec_time_namespaces(ns->ucounts);
put_user_ns(ns->user_ns);
ns_free_inum(&ns->ns);
kfree(ns);
}
static struct time_namespace *to_time_ns(struct ns_common *ns)
{
return container_of(ns, struct time_namespace, ns);
}
static struct ns_common *timens_get(struct task_struct *task)
{
struct time_namespace *ns = NULL;
struct nsproxy *nsproxy;
task_lock(task);
nsproxy = task->nsproxy;
if (nsproxy) {
ns = nsproxy->time_ns;
get_time_ns(ns);
}
task_unlock(task);
return ns ? &ns->ns : NULL;
}
static struct ns_common *timens_for_children_get(struct task_struct *task)
{
struct time_namespace *ns = NULL;
struct nsproxy *nsproxy;
task_lock(task);
nsproxy = task->nsproxy;
if (nsproxy) {
ns = nsproxy->time_ns_for_children;
get_time_ns(ns);
}
task_unlock(task);
return ns ? &ns->ns : NULL;
}
static void timens_put(struct ns_common *ns)
{
put_time_ns(to_time_ns(ns));
}
static int timens_install(struct nsproxy *nsproxy, struct ns_common *new)
{
struct time_namespace *ns = to_time_ns(new);
if (!current_is_single_threaded())
return -EUSERS;
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
return -EPERM;
get_time_ns(ns);
put_time_ns(nsproxy->time_ns);
nsproxy->time_ns = ns;
get_time_ns(ns);
put_time_ns(nsproxy->time_ns_for_children);
nsproxy->time_ns_for_children = ns;
return 0;
}
int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
{
struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
struct time_namespace *ns = to_time_ns(nsc);
/* create_new_namespaces() already incremented the ref counter */
if (nsproxy->time_ns == nsproxy->time_ns_for_children)
return 0;
get_time_ns(ns);
put_time_ns(nsproxy->time_ns);
nsproxy->time_ns = ns;
return 0;
}
static struct user_namespace *timens_owner(struct ns_common *ns)
{
return to_time_ns(ns)->user_ns;
}
const struct proc_ns_operations timens_operations = {
.name = "time",
.type = CLONE_NEWTIME,
.get = timens_get,
.put = timens_put,
.install = timens_install,
.owner = timens_owner,
};
const struct proc_ns_operations timens_for_children_operations = {
.name = "time_for_children",
.type = CLONE_NEWTIME,
.get = timens_for_children_get,
.put = timens_put,
.install = timens_install,
.owner = timens_owner,
};
struct time_namespace init_time_ns = {
.kref = KREF_INIT(3),
.user_ns = &init_user_ns,
.ns.inum = PROC_TIME_INIT_INO,
.ns.ops = &timens_operations,
};
static int __init time_ns_init(void)
{
return 0;
}
subsys_initcall(time_ns_init);
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