linux-kernel - Re: [bug, netconsole, SLUB] BUG skbuff_head

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Message-ID: <19f34abd0807211323o11f38bf6ja756d196da1d7a1f@mail.gmail.com>
Date:	Mon, 21 Jul 2008 22:23:34 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Christoph Lameter" <cl@...ux-foundation.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Evgeniy Polyakov" <johnpol@....mipt.ru>,
	"Pekka Enberg" <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, davem@...emloft.net
Subject: Re: [bug, netconsole, SLUB] BUG skbuff_head_cache: Poison overwritten

On Mon, Jul 21, 2008 at 6:19 PM, Christoph Lameter
<cl@...ux-foundation.org> wrote:
>> (There was recently an odd case of kzalloc() succeeding even though it
>> was called before the slab caches were initialized -- and it only
>> generated a warning about irqs-on happening too early. I just mean to
>> say that it _can_ happen. On another machine, it crashed
>> spectacularly. I guess you're not enabling the netconsole before slab
>> allocator is up?)
>
> Kzalloc for objects > 4k will succeed even during early boot since we will
> directly call into the page allocator.

It wasn't just that; it got into __slab_alloc() and out again. See the
backtrace at http://lkml.org/lkml/2008/7/19/23

It's scary, I know. It's a good thing we have irqtrace :-)


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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