linux-kernel - Re: [PATCH 2/2] efi: Validate UEFI boot variables

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Message-ID: <20120501003156.GA9543@srcf.ucam.org>
Date:	Tue, 1 May 2012 01:31:56 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Shea Levy <shea@...alevy.com>
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 2/2] efi: Validate UEFI boot variables

On Mon, Apr 30, 2012 at 08:00:30PM -0400, Shea Levy wrote:
> On 04/30/2012 04:11 PM, Matthew Garrett wrote:
> >A common flaw in UEFI systems is a refusal to POST triggered by a malformed
> >boot variable. Once in this state, machines may only be restored by
> >reflashing their firmware with an external hardware device. While this is
> >obviously a firmware bug, the serious nature of the outcome suggests that
> >operating systems should filter their variable writes in order to prevent
> >a malicious user from rendering the machine unusable.
> 
> Any chance this will make it safe to use efibootmgr on Apple EFI
> firmware? I've been afraid to use it because I've read it can
> silently brick the device due to a mistake in efibootmgr. Obviously
> this won't correct that mistake, but with this applied should a
> successful variable set imply that the firmware wasn't bricked?

As far as I know that's been fixed since 
202f9d0a41809e3424af5f61489b48b622824aed - the problem wasn't 
efibootmgr, the problem was Apple's firmware overwriting itself.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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