linux-kernel - Re: [PATCH 1/1] pid_namespace: pidns_get() should check task_active_pid

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Message-ID: <20140402155850.GA30570@redhat.com>
Date:	Wed, 2 Apr 2014 17:58:50 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Matthew Dempsky <mdempsky@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Julien Tinnes <jln@...omium.org>,
	Roland McGrath <mcgrathr@...omium.org>,
	Jan Kratochvil <jan.kratochvil@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] pid_namespace: pidns_get() should check
	task_active_pid_ns() != NULL

On 04/02, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@...hat.com> writes:
>
> > pidns_get()->get_pid_ns() can hit ns == NULL. This task_struct can't
> > go away, but task_active_pid_ns(task) is NULL if release_task(task)
> > was already called. Alternatively we could change get_pid_ns(ns) to
> > check ns != NULL, but it seems that other callers are fine.
>
> get_pid_ns already has a ns == NULL check, so no code changes should be
> needed.

Hmm...

	static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
	{
		if (ns != &init_pid_ns)
			kref_get(&ns->kref);
		return ns;
	}

?

Oleg.

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