linux-kernel - Re: [PATCH] Fix EDD3.0 data verification.

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Date:	Wed, 2 Feb 2011 15:38:58 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Subject: Re: [PATCH] Fix EDD3.0 data verification.

On Wed, Feb 02, 2011 at 11:30:36AM -0200, Henrique de Moraes Holschuh wrote:
> On Wed, 02 Feb 2011, Gleb Natapov wrote:
> > Check for nonzero path in edd_has_edd30() has no sense. First, it looks
> > at the wrong memory. Device path starts at offset 30 of the info->params
> > structure which is at offset 8 from the beginning of info structure, but
> > code looks at info + 4 instead. This was correct when code was introduced,
> > but around v2.6.4 three more fields were added to edd_info structure
> > (commit 66b61a5c in history.git). Second, even if it will check correct
> > memory it will always succeed since at offset 30 (params->key) there will
> > be non-zero values otherwise previous check would fail.
> 
> Hmm, would that be a reason for boot lockups on some systems ?  I've
> seen that happen on Intel D875PBZ and Debian stable (2.6.26).  We
> dropped EDD support then.
> 
Unlikely. Edd module is not loaded by default and the code that the
patch changes works on in-memory data that was read from BIOS during
boot. It is theoretically possible that BIOS, that works according to
phoenix spec, will do something bad when int13_48 is called with buffer
bigger then 66 bytes, but my patch does not fix that.

--
			Gleb.
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