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

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Message-ID: <84144f020807180215p4c3e9fadl75c478f1aacea35f@mail.gmail.com>
Date:	Fri, 18 Jul 2008 12:15:26 +0300
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Evgeniy Polyakov" <johnpol@....mipt.ru>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	"Vegard Nossum" <vegard.nossum@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [bug, netconsole, SLUB] BUG skbuff_head_cache: Poison overwritten

Hi Ingo,

On Fri, Jul 18, 2008 at 12:09 PM, Ingo Molnar <mingo@...e.hu> wrote:
> yeah, we want to check use-after free at the next allocation point -
> i.e. as late as possible to gather all corruptions that happened
> meanwhile.
>
> We could in theory have a SLUB debug mode where a SCHED_IDLE kernel
> thread would periodically check all free objects (of that CPU) in the
> background to ensure their integrity. That would catch corruptions
> sooner, with a possibly still meaningful context to print out. [right
> after the IRQ or process that corrupts them finishes running]
>
> It could also be hooked into ftrace to print out the last few hundred
> kernel function calls executed prior any corruption. ftrace/slub-debug
> plugin perhaps?

Well, there's this Norwegian guy, Vegard, who has written a small
piece of code that can detect use-after-free _as it happens_. I think
he calls the thing kmemcheck :-).
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