From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55848C00449 for ; Wed, 3 Oct 2018 21:21:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18ED221470 for ; Wed, 3 Oct 2018 21:21:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18ED221470 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727109AbeJDELc (ORCPT ); Thu, 4 Oct 2018 00:11:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39648 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725871AbeJDELc (ORCPT ); Thu, 4 Oct 2018 00:11:32 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 28AB1308FBA3; Wed, 3 Oct 2018 21:21:27 +0000 (UTC) Received: from asgard.redhat.com (ovpn-200-17.brq.redhat.com [10.40.200.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8E5B0589B; Wed, 3 Oct 2018 21:21:16 +0000 (UTC) Date: Wed, 3 Oct 2018 23:21:44 +0200 From: Eugene Syromiatnikov To: Jann Horn Cc: yu-cheng.yu@intel.com, Andy Lutomirski , the arch/x86 maintainers , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , rdunlap@infradead.org, ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com Subject: Re: [RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs Message-ID: <20181003212029.GH32759@asgard.redhat.com> References: <20180921150351.20898-1-yu-cheng.yu@intel.com> <20180921150351.20898-25-yu-cheng.yu@intel.com> <20181003045611.GB22724@asgard.redhat.com> <5ddb0ad33298d1858e530fce9c9ea2788b2fac81.camel@intel.com> <20181003163226.GC9449@asgard.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Wed, 03 Oct 2018 21:21:27 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 03, 2018 at 06:52:40PM +0200, Jann Horn wrote: > On Wed, Oct 3, 2018 at 6:32 PM Eugene Syromiatnikov wrote: > > I'm not sure, however, whether such a change that provides no ability > > to configure or affect it will go well with all the supported > > architectures. > > Is there a concrete reason why you think an architecture might not > like this? As far as I can tell, the virtual address space overhead > should be insignificant even for 32-bit systems. Not really, and not architectures per se, but judging by some past experiences with enabling ASLR, I would expect that all kinds of weird applications may start to behave in all kinds of strange ways. Not that I have anything more than this doubt, however; but this sort of change without any ability to tune or revert it still looks unusual to me.