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Date: Wed, 2 Apr 2014 17:58:50 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Matthew Dempsky <mdempsky@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>, Julien Tinnes <jln@chromium.org>,
        Roland McGrath <mcgrathr@chromium.org>,
        Jan Kratochvil <jan.kratochvil@redhat.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] pid_namespace: pidns_get() should check
	task_active_pid_ns() != NULL
Message-ID: <20140402155850.GA30570@redhat.com>
References: <CAF52+S6Y40K-sRPf4YAb8ceAmtgBzZ9OUbyhPTOc_AcOWuQ=Ng@mail.gmail.com> <1396391358-22367-1-git-send-email-mdempsky@chromium.org> <20140402145850.GB7332@redhat.com> <20140402154447.GA29857@redhat.com> <20140402154505.GB29857@redhat.com> <87eh1fisfm.fsf@x220.int.ebiederm.org>
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On 04/02, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@redhat.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.