From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757744Ab2EAAcE (ORCPT ); Mon, 30 Apr 2012 20:32:04 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:56257 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756896Ab2EAAcC (ORCPT ); Mon, 30 Apr 2012 20:32:02 -0400 Date: Tue, 1 May 2012 01:31:56 +0100 From: Matthew Garrett To: Shea Levy Cc: torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 2/2] efi: Validate UEFI boot variables Message-ID: <20120501003156.GA9543@srcf.ucam.org> References: <1335816690-26019-1-git-send-email-mjg@redhat.com> <1335816690-26019-2-git-send-email-mjg@redhat.com> <4F9F279E.606@shealevy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F9F279E.606@shealevy.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: mjg59@cavan.codon.org.uk X-SA-Exim-Scanned: No (on cavan.codon.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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@srcf.ucam.org