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=-3.8 required=3.0 tests=BAYES_00, 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 18D71C5517A for ; Tue, 3 Nov 2020 13:52:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB2F522226 for ; Tue, 3 Nov 2020 13:52:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729522AbgKCNwa (ORCPT ); Tue, 3 Nov 2020 08:52:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729362AbgKCNw0 (ORCPT ); Tue, 3 Nov 2020 08:52:26 -0500 Received: from mout-p-202.mailbox.org (mout-p-202.mailbox.org [IPv6:2001:67c:2050::465:202]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17C31C0613D1; Tue, 3 Nov 2020 05:52:26 -0800 (PST) Received: from smtp2.mailbox.org (smtp2.mailbox.org [80.241.60.241]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-202.mailbox.org (Postfix) with ESMTPS id 4CQWS671PfzQkKw; Tue, 3 Nov 2020 14:52:22 +0100 (CET) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by spamfilter06.heinlein-hosting.de (spamfilter06.heinlein-hosting.de [80.241.56.125]) (amavisd-new, port 10030) with ESMTP id FlqcKCn97r9e; Tue, 3 Nov 2020 14:52:18 +0100 (CET) Date: Tue, 3 Nov 2020 14:52:14 +0100 (CET) From: Hagen Paul Pfeifer To: Mike Rapoport Cc: Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , David Hildenbrand , Elena Reshetova , "H. Peter Anvin" , Idan Yaniv , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Thomas Gleixner , Shuah Khan , 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 Message-ID: <1547601988.128687.1604411534845@office.mailbox.org> In-Reply-To: <20201102154028.GD4879@kernel.org> References: <20200924132904.1391-1-rppt@kernel.org> <20201101110935.GA4105325@laniakea> <20201102154028.GD4879@kernel.org> Subject: Re: [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Priority: 3 Importance: Normal X-MBO-SPAM-Probability: X-Rspamd-Score: -0.65 / 15.00 / 15.00 X-Rspamd-Queue-Id: D612C1723 X-Rspamd-UID: 9101f0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On 11/02/2020 4:40 PM Mike Rapoport wrote: > > Isn't memfd_secret currently *unnecessarily* designed to be a "one task > > feature"? memfd_secret fulfills exactly two (generic) features: > > > > - address space isolation from kernel (aka SECRET_EXCLUSIVE, not in kernel's > > direct map) - hide from kernel, great > > - disabling processor's memory caches against speculative-execution vulnerabilities > > (spectre and friends, aka SECRET_UNCACHED), also great > > > > But, what about the following use-case: implementing a hardened IPC mechanism > > where even the kernel is not aware of any data and optionally via SECRET_UNCACHED > > even the hardware caches are bypassed! With the patches we are so close to > > achieving this. > > > > How? Shared, SECRET_EXCLUSIVE and SECRET_UNCACHED mmaped pages for IPC > > involved tasks required to know this mapping (and memfd_secret fd). After IPC > > is done, tasks can copy sensitive data from IPC pages into memfd_secret() > > pages, un-sensitive data can be used/copied everywhere. > > As long as the task share the file descriptor, they can share the > secretmem pages, pretty much like normal memfd. Including process_vm_readv() and process_vm_writev()? Let's take a hypothetical "dbus-daemon-secure" service that receives data from process A and wants to copy/distribute it to data areas of N other processes. Much like dbus but without SOCK_DGRAM rather direct copy into secretmem/mmap pages (ring-buffer). Should be possible, right? > > One missing piece is still the secure zeroization of the page(s) if the > > mapping is closed by last process to guarantee a secure cleanup. This can > > probably done as an general mmap feature, not coupled to memfd_secret() and > > can be done independently ("reverse" MAP_UNINITIALIZED feature). > > There are "init_on_alloc" and "init_on_free" kernel parameters that > enable zeroing of the pages on alloc and on free globally. > Anyway, I'll add zeroing of the freed memory to secretmem. Great, this allows page-specific (thus runtime-performance-optimized) zeroing of secured pages. init_on_free lowers the performance to much and is not precice enough. Hagen