From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eugene Syromiatnikov Subject: Re: [RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs Date: Wed, 3 Oct 2018 23:21:44 +0200 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 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-arch.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. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 Date: Wed, 3 Oct 2018 23:21:44 +0200 From: Eugene Syromiatnikov 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: Sender: linux-arch-owner@vger.kernel.org List-ID: 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 Message-ID: <20181003212144.v_e8KGAA97P2twHxoNwNuXiSaHyzz2D9i2EAWaGQUKU@z> 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.