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

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Message-ID: <alpine.DEB.2.00.1111230916220.16139@router.home>
Date:	Wed, 23 Nov 2011 09:17:14 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Pekka Enberg <penberg@...nel.org>
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, 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?

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