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Date: Fri, 25 Jan 2013 14:53:29 +0000
From: Christoph Lameter <cl@linux.com>
Subject: Re: FIX [1/2] slub: Do not dereference NULL pointer in node_match
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To: Simon Jeons <simon.jeons@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>, Steven Rostedt <rostedt@goodmis.org>, Thomas Gleixner <tglx@linutronix.de>, RT <linux-rt-users@vger.kernel.org>, Clark Williams <clark@redhat.com>, John Kacur <jkacur@gmail.com>, "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>, Joonsoo Kim <js1304@gmail.com>, Glauber Costa <glommer@parallels.com>, linux-mm@kvack.org, David Rientjes <rientjes@google.com>, elezegarcia@gmail.com

On Fri, 25 Jan 2013, Simon Jeons wrote:

> >
> > node_match(NULL, xx) = 0
> >
> >  	->
> >
> > call into __slab_alloc.
> >
> > __slab_alloc() will check for !c->page which requires the assignment of a
> > new per cpu slab page.
> >
>
> But there are dereference in page_to_nid path, function page_to_section:
> return (page->flags >> SECTIONS_PGSHIFT) & SECTIONS_MASK;

node_match() checks for NULL and will not invoke page_to_nid for a NULL
pointer.

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