linux-kernel - Re: PROBLEM: memory corrupting bug, bisected to 6dda9d55

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Date:	Mon, 11 Oct 2010 14:00:39 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	pacman@...h.dhis.org, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: PROBLEM: memory corrupting bug, bisected to 6dda9d55

(cc linuxppc-dev@...ts.ozlabs.org)

On Mon, 11 Oct 2010 15:30:22 +0100
Mel Gorman <mel@....ul.ie> wrote:

> On Sat, Oct 09, 2010 at 04:57:18AM -0500, pacman@...h.dhis.org wrote:
> > (What a big Cc: list... scripts/get_maintainer.pl made me do it.)
> > 
> > This will be a long story with a weak conclusion, sorry about that, but it's
> > been a long bug-hunt.
> > 
> > With recent kernels I've seen a bug that appears to corrupt random 4-byte
> > chunks of memory. It's not easy to reproduce. It seems to happen only once
> > per boot, pretty quickly after userspace has gotten started, and sometimes it
> > doesn't happen at all.
> > 
> 
> A corruption of 4 bytes could be consistent with a pointer value being
> written to an incorrect location.

It's corruption of user memory, which is unusual.  I'd be wondering if
there was a pre-existing bug which 6dda9d55bf545013597 has exposed -
previously the corruption was hitting something harmless.  Something
like a missed CPU cache writeback or invalidate operation.

How sensitive/vulnerable is PPC32 to such things?
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