linux-kernel - Re: [PATCH 07/11] Memory compaction core

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Date:	Wed, 24 Mar 2010 16:19:24 -0500 (CDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Jonathan Corbet <corbet@....net>, Mel Gorman <mel@....ul.ie>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 07/11] Memory compaction core

On Wed, 24 Mar 2010, Andrew Morton wrote:

> > ...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.

If the object pointed to is larger than page size and we are
referencing a member with an offset larger than page size later then we
may create an exploit without checks.

But the structure here is certainly smaller than that. So no issue here.



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