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Date: Wed, 24 Mar 2010 14:14:00 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Mel Gorman <mel@csn.ul.ie>, Andrea Arcangeli <aarcange@redhat.com>,
       Christoph Lameter <cl@linux-foundation.org>,
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       Rik van Riel <riel@redhat.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org
Subject: Re: [PATCH 07/11] Memory compaction core
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On Wed, 24 Mar 2010 14:59:46 -0600
Jonathan Corbet <corbet@lwn.net> wrote:

> On Wed, 24 Mar 2010 13:33:47 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > > +	VM_BUG_ON(cc == NULL);  
> > 
> > It's a bit strange to test this when we're about to oops anyway.  The
> > oops will tell us the same thing.
> 
> ...except that we've seen a fair number of null pointer dereference
> exploits that have told us something altogether different.  Are we
> *sure* we don't want to test for null pointers...?
> 

It's hard to see what the test gains us really - the kernel has
zillions of pointer derefs, any of which could be NULL if we have a
bug.  Are we more likely to have a bug here than elsewhere?

This one will oops on a plain old read, so it's a bit moot in this
case.