linux-kernel - Re: [RFC][PATCH] slub: Check for page NULL before doing the node

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Message-ID: <0000013c4a64146b-68cd6f7d-f7e2-460b-9ee5-d931714ce062-000000@email.amazonses.com>
Date:	Thu, 17 Jan 2013 21:22:18 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Steven Rostedt <rostedt@...dmis.org>
cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	RT <linux-rt-users@...r.kernel.org>,
	Clark Williams <clark@...hat.com>,
	John Kacur <jkacur@...il.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
Subject: Re: [RFC][PATCH] slub: Check for page NULL before doing the node_match
 check

On Thu, 17 Jan 2013, Steven Rostedt wrote:

> Anyway, looking at where this crashed, it seems that the page variable
> can be NULL when passed to the node_match() function (which does not
> check if it is NULL). When this happens we get the above panic.
>
> As page is only used in slab_alloc() to check if the node matches, if
> it's NULL I'm assuming that we can say it doesn't and call the
> __slab_alloc() code. Is this a correct assumption?

c->page should only be NULL when c->freelist == NULL but obviously there
are race conditions where c->freelist may not have been zapped but c->page
was.

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