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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 981EFC388F9 for ; Tue, 3 Nov 2020 16:30:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 444062072C for ; Tue, 3 Nov 2020 16:30:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604421019; bh=jYHfX66WW2BdNqS2XWf0ysCG2+5llIa7XFBTFdDX/eI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=b6t2npVfr1XeuBK1zQNnjLd8ihub2c0qJgrgDntOh5i+j2YmyMvCITbsfvG70W1Ju T2Ag4W3w/1OsGXjbjpqxcSENR34xFwgS5gy94gIP7emf8ZDWv/Kwo2ql2maIjoliO7 ocj7ot4UHo6WxP5fGW3+22fybQG4gRLbbuJsyino= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728419AbgKCQaS (ORCPT ); Tue, 3 Nov 2020 11:30:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:53470 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728082AbgKCQaS (ORCPT ); Tue, 3 Nov 2020 11:30:18 -0500 Received: from kernel.org (unknown [87.71.17.26]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8FB1C206DF; Tue, 3 Nov 2020 16:30:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604421016; bh=jYHfX66WW2BdNqS2XWf0ysCG2+5llIa7XFBTFdDX/eI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=aIT9WT+BvHALjjzBR+JANCva7x0iax3JsHcWBCEfbBEXiFyByvncM0vQDEjoMsNzh qIUHx4c/P1fmtrQLv9EIQHUB/NNPUa0sJ3XCbfY5Co0b/q6PUKAT7BitPwWCXDu5+c 05kTyD2Qgu6hQisAN/yBj1hMLhxnioRXXIEvqYek= Date: Tue, 3 Nov 2020 18:30:02 +0200 From: Mike Rapoport To: Hagen Paul Pfeifer 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 Subject: Re: [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <20201103163002.GK4879@kernel.org> References: <20200924132904.1391-1-rppt@kernel.org> <20201101110935.GA4105325@laniakea> <20201102154028.GD4879@kernel.org> <1547601988.128687.1604411534845@office.mailbox.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1547601988.128687.1604411534845@office.mailbox.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 03, 2020 at 02:52:14PM +0100, Hagen Paul Pfeifer wrote: > > 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? I'm not sure I follow you here. For process_vm_readv() and process_vm_writev() secremem will be only accessible on the local part, but not on the remote. So copying data to secretmem pages using process_vm_writev wouldn't work. > > > 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 -- Sincerely yours, Mike.