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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 614C4C433E0 for ; Mon, 15 Feb 2021 09:15:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18F9264E68 for ; Mon, 15 Feb 2021 09:15:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229764AbhBOJOz (ORCPT ); Mon, 15 Feb 2021 04:14:55 -0500 Received: from mx2.suse.de ([195.135.220.15]:33862 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230088AbhBOJOi (ORCPT ); Mon, 15 Feb 2021 04:14:38 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1613380431; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=miCNDkPWZZBRVJ8Jtr1LFzD24yWA9N0KNTV3BkO+MBs=; b=TETHPiEq8kl7uQEKm1Aff4L3NsQE0DM02/lfPkpKudaCI6/5lNvCven/uHuRT24qzIXWlb R5BxAqdLhSywOBM2nG5lWN1rFZRScNEvDlYO6zf3OlgEc7VuRTl3HqG4uIymDgc/8zHABu C6iAKZCoFVJI6hxssRHEbP17I8dvFo0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9278BAD19; Mon, 15 Feb 2021 09:13:51 +0000 (UTC) Date: Mon, 15 Feb 2021 10:13:50 +0100 From: Michal Hocko To: James Bottomley Cc: David Hildenbrand , Mike Rapoport , Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: References: <20210214091954.GM242749@kernel.org> <052DACE9-986B-424C-AF8E-D6A4277DE635@redhat.com> <244f86cba227fa49ca30cd595c4e5538fe2f7c2b.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <244f86cba227fa49ca30cd595c4e5538fe2f7c2b.camel@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun 14-02-21 11:21:02, James Bottomley wrote: > On Sun, 2021-02-14 at 10:58 +0100, David Hildenbrand wrote: > [...] > > > And here we come to the question "what are the differences that > > > justify a new system call?" and the answer to this is very > > > subjective. And as such we can continue bikeshedding forever. > > > > I think this fits into the existing memfd_create() syscall just fine, > > and I heard no compelling argument why it shouldn‘t. That‘s all I can > > say. > > OK, so let's review history. In the first two incarnations of the > patch, it was an extension of memfd_create(). The specific objection > by Kirill Shutemov was that it doesn't share any code in common with > memfd and so should be a separate system call: > > https://lore.kernel.org/linux-api/20200713105812.dnwtdhsuyj3xbh4f@box/ Thanks for the pointer. But this argument hasn't been challenged at all. It hasn't been brought up that the overlap would be considerable higher by the hugetlb/sealing support. And so far nobody has claimed those combinations as unviable. > The other objection raised offlist is that if we do use memfd_create, > then we have to add all the secret memory flags as an additional ioctl, > whereas they can be specified on open if we do a separate system call. > The container people violently objected to the ioctl because it can't > be properly analysed by seccomp and much preferred the syscall version. > > Since we're dumping the uncached variant, the ioctl problem disappears > but so does the possibility of ever adding it back if we take on the > container peoples' objection. This argues for a separate syscall > because we can add additional features and extend the API with flags > without causing anti-ioctl riots. I am sorry but I do not understand this argument. What kind of flags are we talking about and why would that be a problem with memfd_create interface? Could you be more specific please? -- Michal Hocko SUSE Labs