From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: Re: Do not allow MSR or Embedded Controller writes from userspace in secure boot case Date: Wed, 7 Nov 2012 23:21:33 +0000 Message-ID: <20121107232133.12f94cfe@pyramind.ukuu.org.uk> References: <1352323699-52400-1-git-send-email-trenn@suse.de> <20121107215403.GA7277@srcf.ucam.org> <509AE5DA.1030508@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <509AE5DA.1030508-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "H. Peter Anvin" Cc: Matthew Garrett , Thomas Renninger , linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, jlee-IBi9RG/b67k@public.gmane.org List-Id: linux-efi@vger.kernel.org On Wed, 07 Nov 2012 23:51:06 +0100 "H. Peter Anvin" wrote: > On 11/07/2012 10:54 PM, Matthew Garrett wrote: > > Is there a case where modifying MSRs or EC registers can cause arbitrary > > code execution? > > For MSRs we could have a whitelist of permitted MSRs, but allowing > general MSR access... no. Far safer to just block it and expect people to use MSRs accessed via drivers that provide functionality. Otherwise your blacklist in some cases will get fiendishly complicated and sometimes depend upon the exact chip and the values in other MSRs as to whether they are safe. Alan