netdev - Re: [PATCH 2.6.30-rc5] ehea: fix invalid pointer access

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Date:	Tue, 5 May 2009 13:19:05 +0200
From:	Hannes Hering <hannes.hering@...ux.vnet.ibm.com>
To:	David Howells <dhowells@...hat.com>
Cc:	David Miller <davem@...emloft.net>, themann@...ibm.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	raisch@...ibm.com, ossrosch@...ux.vnet.ibm.com,
	linuxppc-dev@...abs.org, ossthema@...ibm.com, osstklei@...ibm.com
Subject: Re: [PATCH 2.6.30-rc5] ehea: fix invalid pointer access

On Tuesday 05 May 2009 11:11:27 David Howells wrote:
> Hannes Hering <hannes.hering@...ux.vnet.ibm.com> wrote:
> 
> >  	pref = skb_array[x];
> > -	prefetchw(pref);
> > -	prefetchw(pref + EHEA_CACHE_LINE);
> > +	if (pref) {
> > +		prefetchw(pref);
> > +		prefetchw(pref + EHEA_CACHE_LINE);
> 
> Ummm...  Is prefetch() or prefetchw() faulting?
> 
> David
Hi David,

this is an ehea driver problem, which is occuring when the receive queue runs
empty. The faulting code is more specifically the following line:

	pref = (skb_array[x]->data);

Here the access to the struct element data would cause an exception.We could
have made the if block a little smaller.

Regards

Hannes
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