Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758312AbcCCVX2 (ORCPT ); Thu, 3 Mar 2016 16:23:28 -0500 Received: from torg.zytor.com ([198.137.202.12]:53280 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753817AbcCCVX1 (ORCPT ); Thu, 3 Mar 2016 16:23:27 -0500 Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack To: Borislav Petkov References: <20160302214654.GK8362@pd.tnic> <56D7612A.4080107@zytor.com> <20160302220954.GL8362@pd.tnic> <56D76527.5020806@zytor.com> <20160302222842.GM8362@pd.tnic> <20160303122836.GC24621@pd.tnic> <395B06E1-314F-4F8A-9C89-57F8E4A61B3D@zytor.com> <20160303162952.GE24621@pd.tnic> <56D89CEE.9070406@zytor.com> <20160303205437.GA13505@pd.tnic> Cc: Brian Gerst , X86 ML , LKML , Tom Lendacky From: "H. Peter Anvin" Message-ID: <56D8AB33.1050206@zytor.com> Date: Thu, 3 Mar 2016 13:22:59 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160303205437.GA13505@pd.tnic> 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 Content-Length: 480 Lines: 14 On 03/03/16 12:54, Borislav Petkov wrote: > On Thu, Mar 03, 2016 at 12:22:06PM -0800, H. Peter Anvin wrote: >> The only thing I can think of is that the -8 creates a null pointer that >> terminates a stack trace. > > Probably not needed anymore as print_context_stack()->valid_stack_ptr() > in dumpstack.c look at the stack boundaries instead of checking for > NULL... > Sure, but it could still affect kgdb or what not. That's the only reason I can see for -8 though. -hpa