[CRIU] [PATCHv6 01/36] ns: Introduce Time Namespace

[Thomas Gleixner]

Dmitry,

On Thu, 15 Aug 2019, Dmitry Safonov wrote:
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 420567d1519a..97b7737f5aba 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12898,6 +12898,8 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
>  S:	Maintained
>  F:	fs/timerfd.c
>  F:	include/linux/timer*
> +F:	include/linux/time_namespace.h
> +F:	kernel/time_namespace.c

Shouldn't this be kernel/time/namespace.c so all that stuff is lumped
together. No strong opinion though.

> +++ b/kernel/time_namespace.c
> +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);
> +}
> +
> +static struct time_namespace *create_time_ns(void)
> +{
> +	struct time_namespace *time_ns;
> +
> +	time_ns = kmalloc(sizeof(struct time_namespace), GFP_KERNEL);

Shouldn't this use kzalloc()? There are tons of members in that struct.

> +	if (time_ns) {
> +		kref_init(&time_ns->kref);
> +		time_ns->initialized = false;

And you spare this one.

> +	}
> +	return time_ns;
> +}
> +
> +/*
> + * Clone a new ns copying @old_ns, setting refcount to 1
> + * @old_ns: namespace to clone
> + * Return the new ns or ERR_PTR.

If you use kernel-doc style then please use te proper syntax

/*
 * clone_time_ns - Clone a time 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 = create_time_ns();
> +	if (!ns)
> +		goto fail_dec;
> +
> +	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);
> +	return ns;
> +
> +fail_free:
> +	kfree(ns);
> +fail_dec:
> +	dec_time_namespaces(ucounts);
> +fail:
> +	return ERR_PTR(err);
> +}
> +
> +/*
> + * Add a reference to old_ns, or clone it if @flags specify CLONE_NEWTIME.
> + * In latter case, changes to the time of this process won't be seen by parent,
> + * and vice versa.

Ditto

> + */
> +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);
> +	get_time_ns(ns);

Why is this a double get?

> +	put_time_ns(nsproxy->time_ns);
> +	put_time_ns(nsproxy->time_ns_for_children);
> +	nsproxy->time_ns = ns;
> +	nsproxy->time_ns_for_children = ns;
> +	ns->initialized = true;
> +	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);
> +
> +	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;
> +	ns->initialized = true;

Isn't that one initialized already?

> +
> +	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,
> +};

Inconsisten formatting. The above static initializers are nicely
tabular. This on not.

Thanks,

	tglx