linux-kernel - Re: [RFC PATCH 02/12] On Tue, 23 Sep 2008, David Miller wrote:

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Message-ID: <alpine.LFD.2.00.0810051752210.3398@apollo>
Date:	Sun, 5 Oct 2008 17:55:14 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arjan van de Ven <arjan@...ux.intel.com>
cc:	Jesse Brandeburg <jesse.brandeburg@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	David Miller <davem@...emloft.net>, jesse.brandeburg@...el.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	kkeil@...e.de, agospoda@...hat.com, david.graham@...el.com,
	bruce.w.allan@...el.com, john.ronciak@...el.com,
	chris.jones@...onical.com, tim.gardner@...onical.com,
	airlied@...il.com, Olaf Kirch <okir@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC PATCH 02/12] On Tue, 23 Sep 2008, David Miller wrote:

On Sun, 5 Oct 2008, Arjan van de Ven wrote:
> Thomas Gleixner wrote:
> > On Sat, 4 Oct 2008, Jesse Brandeburg wrote:
> > > > Exactly. The access to a ro region results in a fault. I have nowhere
> > > > seen that trigger, but I can reproduce the trylock() WARN_ON, which
> > > > confirms that there is concurrent access to the NVRAM registers. The
> > > > backtrace pattern is similar to the one you have seen.
> > > are you still getting WARN_ON *with* all the mutex based fixes already
> > > applied?
> > 
> > The WARN_ON triggers with current mainline. Is there any fixlet in
> > Linus tree missing ?
> > 
> > > with the mutex patches in place (without protection patch) we are
> > > still reproducing the issue, until we apply the set_memory_ro patch.
> > 
> > That does not make sense to me. If the memory_ro patch is providing
> > _real_ protection then you _must_ run into an access violation. If not,
> > then the patch just papers over the real problem in some mysterious
> > way.
> > 
> 
> not if the bad code is doing copy_to_user .... (or similar)

You mean: copy_from_user :) This would require that the e1000e
nvram region is writable via copy_from_user by an e1000e user space
interface. A quick grep does not reviel such a horrible interface.

Thanks,

	tglx
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