From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f179.google.com (mail-io0-f179.google.com [209.85.223.179]) by kanga.kvack.org (Postfix) with ESMTP id 319486B0253 for ; Sun, 8 Nov 2015 22:47:59 -0500 (EST) Received: by iodd200 with SMTP id d200so174270306iod.0 for ; Sun, 08 Nov 2015 19:47:59 -0800 (PST) Received: from ozlabs.org (ozlabs.org. [2401:3900:2:1::2]) by mx.google.com with ESMTPS id jf3si8882254igb.26.2015.11.08.19.47.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 08 Nov 2015 19:47:57 -0800 (PST) Message-ID: <1447040874.5195.2.camel@ellerman.id.au> Subject: Re: [PATCH v2 2/2] arm: mm: support ARCH_MMAP_RND_BITS. From: Michael Ellerman Date: Mon, 09 Nov 2015 14:47:54 +1100 In-Reply-To: References: <1446574204-15567-1-git-send-email-dcashman@android.com> <1446574204-15567-2-git-send-email-dcashman@android.com> <56393FD0.6080001@android.com> <563A4EDC.6090403@android.com> <563BA393.9020504@android.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Kees Cook , Daniel Cashman Cc: LKML , Russell King - ARM Linux , Andrew Morton , Ingo Molnar , "linux-arm-kernel@lists.infradead.org" , Jonathan Corbet , Don Zickus , "Eric W. Biederman" , Heinrich Schuchardt , jpoimboe@redhat.com, "Kirill A. Shutemov" , n-horiguchi@ah.jp.nec.com, Andrea Arcangeli , Mel Gorman , Thomas Gleixner , David Rientjes , Linux-MM , "linux-doc@vger.kernel.org" , Mark Salyzyn , Jeffrey Vander Stoep , Nick Kralevich , dcashman On Fri, 2015-11-06 at 12:52 -0800, Kees Cook wrote: > On Thu, Nov 5, 2015 at 10:44 AM, Daniel Cashman wrote: > > On 11/04/2015 10:30 AM, Daniel Cashman wrote: > > > On 11/3/15 3:21 PM, Kees Cook wrote: > > > > On Tue, Nov 3, 2015 at 3:14 PM, Daniel Cashman wrote: > > > > > On 11/03/2015 11:19 AM, Kees Cook wrote: > > > > > > Do you have patches for x86 and arm64? > > > > > > > > > > I was holding off on those until I could gauge upstream reception. If > > > > > desired, I could put those together and add them as [PATCH 3/4] and > > > > > [PATCH 4/4]. > > > > > > > > If they're as trivial as I'm hoping, yeah, let's toss them in now. If > > > > not, skip 'em. PowerPC, MIPS, and s390 should be relatively simple > > > > too, but one or two of those have somewhat stranger calculations when > > > > I looked, so their Kconfigs may not be as clean. > > > > > > Creating the patches should be simple, it's the choice of minimum and > > > maximum values for each architecture that I'd be most concerned about. > > > I'll put them together, though, and the ranges can be changed following > > > discussion with those more knowledgeable, if needed. I also don't have > > > devices on which to test the PowerPC, MIPS and s390 changes, so I'll > > > need someone's help for that. > > > > Actually, in preparing the x86 and arm64 patches, it became apparent > > that the current patch-set does not address 32-bit executables running > > on 64-bit systems (compatibility mode), since only one procfs > > mmap_rnd_bits variable is created and exported. Some possible solutions: > > How about a single new CONFIG+sysctl that is the compat delta. For > example, on x86, it's 20 bits. Then we don't get splashed with a whole > new set of min/maxes, but we can reasonably control compat? Do you mean in addition to mmap_rnd_bits? So we'd end up with mmap_rnd_bits and also mmap_rnd_bits_compat_delta? (naming TBD) If so yeah I think that would work. It would have the nice property of allowing you to add some more randomness to all processes by bumping mmap_rnd_bits. But at the same time if you want to add a lot more randomness to 64-bit processes, but just a bit (or none) to 32-bit processes you can also do that. cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org