From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752919AbbC0MO5 (ORCPT ); Fri, 27 Mar 2015 08:14:57 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:35525 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752283AbbC0MOx (ORCPT ); Fri, 27 Mar 2015 08:14:53 -0400 Date: Fri, 27 Mar 2015 13:14:48 +0100 From: Ingo Molnar To: Hector Marco-Gisbert Cc: Borislav Petkov , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Alexander Viro , Jan-Simon , linux-fsdevel@vger.kernel.org, kees Cook , Ismael Ripoll Subject: Re: [PATCH] mm/x86: AMD Bulldozer ASLR fix Message-ID: <20150327121448.GB15631@gmail.com> References: <20150326190800.GF27751@pd.tnic> <1427456301-3764-1-git-send-email-hecmargi@upv.es> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1427456301-3764-1-git-send-email-hecmargi@upv.es> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Hector Marco-Gisbert wrote: > A bug in Linux ASLR implementation which affects some AMD processors > has been found. The issue affects to all Linux process even if they > are not using shared libraries (statically compiled). It's not a bug, it's a feature: to work around a Bulldozer cache aliasing performance problem we have to keep bits 12,13,14 equal for all mappings in the system. Your patch improves upon that fix: by per-boot randomizing the constant portion of the randomized range. Btw., does anyone know how relevant the performance fix is these days? A simpler improvement would be to remove the workaround altogether and recover proper randomization of bits 12,13,14. Thanks, Ingo