From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from imap1.codethink.co.uk ([176.9.8.82]:58983 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750748AbeEOXPk (ORCPT ); Tue, 15 May 2018 19:15:40 -0400 Message-ID: <1526426136.9159.85.camel@codethink.co.uk> Subject: Re: [PATCH 4.4 099/190] arm64: futex: Fix undefined behaviour with FUTEX_OP_OPARG_SHIFT usage From: Ben Hutchings To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Robin Murphy , Will Deacon , Sasha Levin Date: Wed, 16 May 2018 00:15:36 +0100 In-Reply-To: <20180411183556.339662900@linuxfoundation.org> References: <20180411183550.114495991@linuxfoundation.org> <20180411183556.339662900@linuxfoundation.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: On Wed, 2018-04-11 at 20:35 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch.  If anyone has any objections, please let me know. > > ------------------ > > > From: Will Deacon > > > [ Upstream commit 5f16a046f8e144c294ef98cd29d9458b5f8273e5 ] > > FUTEX_OP_OPARG_SHIFT instructs the futex code to treat the 12-bit oparg > field as a shift value, potentially leading to a left shift value that > is negative or with an absolute value that is significantly larger then > the size of the type. UBSAN chokes with: [...] > Whilst I think this catches all of the issues, I'd much prefer to remove > this stuff, as I think it's unused and the bugs are copy-pasted between > a bunch of architectures. [...] Indeed. That more complete fix was done upstream by: commit 30d6e0a4190d37740e9447e4e4815f06992dd8c3 Author: Jiri Slaby Date:   Thu Aug 24 09:31:05 2017 +0200     futex: Remove duplicated code and fix undefined behaviour It's a bit big for stable - though most of the changes are deletions. What do you think? Ben. -- Ben Hutchings Software Developer, Codethink Ltd.