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

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Message-ID: <87a9c3ie66.fsf@x220.int.ebiederm.org>
Date:	Wed, 02 Apr 2014 15:01:37 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Oleg Nesterov <oleg@...hat.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

Oleg Nesterov <oleg@...hat.com> writes:

2> 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;
> 	}
>
> ?

Apparently I could not read this morning, and somehow thought
ns != &init_pid_ns was ns != NULL.


Eric
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