From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754632AbaIDQpK (ORCPT ); Thu, 4 Sep 2014 12:45:10 -0400 Received: from 251.110.2.81.in-addr.arpa ([81.2.110.251]:55506 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754404AbaIDQpG (ORCPT ); Thu, 4 Sep 2014 12:45:06 -0400 Date: Thu, 4 Sep 2014 17:43:40 +0100 From: One Thousand Gnomes To: Austin S Hemmelgarn Cc: Andi Kleen , "H. Peter Anvin" , Linux Kernel Mailing List , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Matthew Garrett Subject: Re: RFC: Tainting the kernel on raw I/O access Message-ID: <20140904174340.24e8bdc0@alan.etchedpixels.co.uk> In-Reply-To: <540872E9.7060608@gmail.com> References: <5407863B.9030608@intel.com> <87tx4op8s5.fsf@tassilo.jf.intel.com> <540872E9.7060608@gmail.com> Organization: Intel Corporation X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > As for the original purpose of taints, I'm not aware of any > > problems with MSR access or port IO causing excessive > > kernel oops reports. Are you? I'm not. From the bugzilla trends I don't think its a major cause, and we can usually root out the "user with dumb external module" problem already. > Really? Either one can be used to modify the running kernel (or > microcode), and possibly even destroy hardware. At least on x86 I would hope not the latter at least on modern systems. So the most irritating thing you can do is probably rootkit the box. It's not as if you can't rootkit a typical distribution shipping Linux system half a dozen other simpler ways than using I/O ports. Besides which once someone has rootkitted your box it won't show the taint anyway ! As a security measure the tainting is next to useless. As a debug aid it's potentially handy. > > If there are none I don't think it makes sense. > > > > At least personally I use MSR accesses quite frequently > > for benign purposes. > But how much of that is just reading MSR's, and of the writes, how much > are either debugging or things that the average user isn't ever going to do? Most of the uses are benign and sensible things like power monitoring tools. Alan