From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756308Ab3LaSnU (ORCPT ); Tue, 31 Dec 2013 13:43:20 -0500 Received: from terminus.zytor.com ([198.137.202.10]:43254 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755555Ab3LaSnP (ORCPT ); Tue, 31 Dec 2013 13:43:15 -0500 Message-ID: <52C31027.2030101@zytor.com> Date: Tue, 31 Dec 2013 10:42:47 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: halfdog , Thomas Gleixner , Ingo Molnar CC: x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: Sanitize CPU-state when switching from virtual-8086 mode to other task References: <52BF4A80.3010503@halfdog.net> <52BF8AEE.6020904@zytor.com> <52C089AC.4000401@halfdog.net> <52C0C9F4.50101@zytor.com> <52C196C3.1040300@halfdog.net> In-Reply-To: <52C196C3.1040300@halfdog.net> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/30/2013 07:52 AM, halfdog wrote: >> >> Still in VirtualBox? > > Yes, again: after comparing the results from initrd on real hardware > with Vbox, I'm getting to understand the timing problem involved and why > timing in VBox is different: The test program usually OOPSes when > touching FPU multiple times, otherwise, when terminated before second > FPU-interacation, it OOPSes on next invocation, stumbling over invalid > CPU state from prior invocation. With improved code, I can rather > reliably bring CPU into that state, so that next process invoked and > touching FPU/MMX-state is OOPSed. Currently searching SUID-binaries and > running UID=0 daemons, that might show interesting reaction on that > event, but only on DOS level yet, e.g. after running V2 test program > once and then connecting via SSH, this currently kills the ssh daemon > nicely. > > It seems that machine lockup occurs when e.g. switch to idle task > happens at exactly the right moment, which I currently cannot trigger on > real hardware, but still working on that. > I'm still wondering if this is a VirtualBox-specific problem or if it is something that *could* occur on hardware, or in other virtualization environments (KVM, Xen HVM, Hy-perV, VMware etc.) -hpa