Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753320AbdHKPYf (ORCPT ); Fri, 11 Aug 2017 11:24:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40642 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752915AbdHKPYd (ORCPT ); Fri, 11 Aug 2017 11:24:33 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 09D70A0C35 Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=fweimer@redhat.com Subject: Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK To: Michal Hocko Cc: =?UTF-8?Q?Colm_MacC=c3=a1rthaigh?= , Kees Cook , Mike Kravetz , Rik van Riel , Will Drewry , akpm@linux-foundation.org, dave.hansen@intel.com, kirill@shutemov.name, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, luto@amacapital.net, mingo@kernel.org References: <20170807134648.GI32434@dhcp22.suse.cz> <1502117991.6577.13.camel@redhat.com> <20170810130531.GS23863@dhcp22.suse.cz> <20170810153639.GB23863@dhcp22.suse.cz> <20170810170144.GA987@dhcp22.suse.cz> <20170811140653.GO30811@dhcp22.suse.cz> <20170811142457.GP30811@dhcp22.suse.cz> From: Florian Weimer Message-ID: <6a04f59b-b72b-c468-ea5c-230764a24402@redhat.com> Date: Fri, 11 Aug 2017 17:24:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170811142457.GP30811@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 11 Aug 2017 15:24:33 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1674 Lines: 34 On 08/11/2017 04:24 PM, Michal Hocko wrote: > On Fri 11-08-17 16:11:44, Florian Weimer wrote: >> On 08/11/2017 04:06 PM, Michal Hocko wrote: >> >>> I am sorry to look too insisting here (I have still hard time to reconcile >>> myself with the madvise (ab)use) but if we in fact want minherit like >>> interface why don't we simply add minherit and make the code which wants >>> to use that interface easier to port? Is the only reason that hooking >>> into madvise is less code? If yes is that a sufficient reason to justify >>> the (ab)use of madvise? If there is a general consensus on that part I >>> will shut up and won't object anymore. Arguably MADV_DONTFORK would fit >>> into minherit API better as well. >> >> It does, OpenBSD calls it MAP_INHERIT_NONE. >> >> Could you implement MAP_INHERIT_COPY and MAP_INHERIT_SHARE as well? Or >> is changing from MAP_SHARED to MAP_PRIVATE and back impossible? > > I haven't explored those two very much. Their semantic seems rather > awkward, especially map_inherit_share one. I guess MAP_INHERIT_COPY > would be doable. Do we have to support all modes or a missing support > would disqualify the syscall completely? I think it would be a bit awkward if we implemented MAP_INHERIT_ZERO and it would not turn a shared mapping into a private mapping in the child, or would not work on shared mappings at all, or deviate in any way from the OpenBSD implementation. MAP_INHERIT_SHARE for a MAP_PRIVATE mapping which has been modified is a bit bizarre, and I don't know how OpenBSD implements any of this. It could well be that the exact behavior implemented in OpenBSD is a poor fit for the Linux VM implementation. Florian