linux-kernel - Re: [PATCH V2] slub: avoid potential NULL dereference or corruption

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Message-ID: <1322083191.1428.125.camel@jaguar>
Date:	Wed, 23 Nov 2011 23:19:51 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Christian Kujau <lists@...dbynature.de>,
	markus@...ppelsdorf.de, David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH V2] slub: avoid potential NULL dereference or corruption

On Wed, 2011-11-23 at 09:17 -0600, Christoph Lameter wrote:
> On Wed, 23 Nov 2011, Pekka Enberg wrote:
> 
> > On Tue, 22 Nov 2011, Eric Dumazet wrote:
> > > show_slab_objects() can trigger NULL dereferences or memory corruption.
> > >
> > > Another cpu can change its c->page to NULL or c->node to NUMA_NO_NODE
> > > while we use them.
> > >
> > > Use ACCESS_ONCE(c->page) and ACCESS_ONCE(c->node) to make sure this
> > > cannot happen.
> > >
> > > Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> >
> > Did someone test this patch? Does it fix any of the reported issues?
> 
> It does not fix any current issues but it is safe against potential
> compiler refetching of variables that we have already checked against
> bad values.
> 
> I thought I acked it already?

Yes, you did. I'm just trying to figure out which ones are going
straight to Linus and which ones can wait for v3.3.

			Pekka

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