linux-kernel - Re: [PATCH] kernel/exit.c: make sure current's nsproxy != NULL while checking caps

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Date:	Thu, 27 Nov 2014 12:01:10 +0100
From:	Lukasz Pawelczyk <l.pawelczyk@...sung.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Lukasz Pawelczyk <havner@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Michal Hocko <mhocko@...e.cz>,
	Sameer Nanda <snanda@...omium.org>,
	Guillaume Morin <guillaume@...infr.org>,
	Li Zefan <lizefan@...wei.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/exit.c: make sure current's nsproxy != NULL while
 checking caps

On śro, 2014-11-26 at 13:32 -0800, David Rientjes wrote:
> On Wed, 26 Nov 2014, Lukasz Pawelczyk wrote:
> > 
> > LSM task_kill() hook is triggered and current->nsproxy within is NULL.
> > 
> > This happens during an exit() syscall because exit_task_namespaces() is
> > called before the exit_notify(). This patch changes their order.
> > 
> 
> This is a classic case of a patch being proposed for a problem that only 
> occurs on kernels that include other patches that are not upstream.  The 
> order that things are deconstructed in the exit path is complex and 
> carefully choreographed, changing it comes at significant risk.  That risk 
> would be justified if a patch were being proposed for upstream that fixes 
> an upstream problem.  It becomes too much of a maintenance nightmare to 
> try to address problems and keep issues from arising for non-upstream 
> patches.  Thus, I don't think this is something that we want.

This is a problem for the change I'm working on and I will be
upstreaming it too at some point. Please see my other reply for more
details:

http://www.spinics.net/lists/kernel/msg1877152.html

The only thing I can do then is to post this patch together with the
other patches when the time comes. But since this issue is rather
separate I've decided to try to push it earlier.



-- 
Lukasz Pawelczyk
Samsung R&D Institute Poland
Samsung Electronics



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