linux-kernel - Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

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Message-ID: <20071226204925.GF8094@elf.ucw.cz>
Date:	Wed, 26 Dec 2007 21:49:25 +0100
From:	Pavel Machek <pavel@....cz>
To:	"H. Peter Anvin" <hpa@...or.com>, security@...nel.org
Cc:	"David P. Reed" <dpreed@...d.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Rene Herman <rene.herman@...access.nl>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80
	on some AMD64x2 laptops, etc.

On Sun 2007-12-16 15:34:58, H. Peter Anvin wrote:
> Pavel Machek wrote:
>> Hi!
>>> The process of safely making delicate changes here is beyond my 
>>> responsibility as just a user - believe me, I'm not suggesting that a 
>>> risky fix be put in .24.   I can patch my own kernels, and I can even 
>>> share an unofficial patch with others for now, or suggest that Fedora and 
>>> Ubuntu add it to their downstream.
>>>
>>> May I make a small suggestion, though.   If the decision is a DMI-keyed 
>>> switch from out-80 to udelay(2)  gets put in, perhaps there should also 
>>> be a way for people to test their own configuration for the underlying 
>>> problem made available as a script.   Though it is a "hack", all you need 
>>> to freeze a problem system is to run a loop doing about 1000 "cat 
>>> /dev/nvram > /dev/null"  commands.  If that leads to a freeze, one might 
>>> ask to have the motherboard added to the DMI-key list.
>> Can you freeze it by catting /dev/rtc, too? That may be significant,
>> because that is readable for group audio (at least on some
>> systems)... which would smell like "small security hole" to me.
>
> Heck, on my system (Fedora 7), it's mode 644...

Ok, time to CC security team, I'd say.

Problem is, that some AMD64x2 nVidia laptops crash on port 0x80
access... which is easily user-triggerable by using /dev/rtc. If it is
644 on Fedora, I guess we have a problem.

Otoh, it is "only" a denial of service, and it can probably be
attributed to "buggy hardware". Is that still relevant for security team?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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