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 7BB76C388F2 for ; Mon, 2 Nov 2020 15:40:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E28232225B for ; Mon, 2 Nov 2020 15:40:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="n0o11Hfl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E28232225B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 33C1E6B0070; Mon, 2 Nov 2020 10:40:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2C5926B0071; Mon, 2 Nov 2020 10:40:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 166606B0072; Mon, 2 Nov 2020 10:40:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0085.hostedemail.com [216.40.44.85]) by kanga.kvack.org (Postfix) with ESMTP id D4DB46B0070 for ; Mon, 2 Nov 2020 10:40:43 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 5FC578249980 for ; Mon, 2 Nov 2020 15:40:43 +0000 (UTC) X-FDA: 77439890766.24.rings96_2e1095d272b1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 49CBA1A4A7 for ; Mon, 2 Nov 2020 15:40:43 +0000 (UTC) X-HE-Tag: rings96_2e1095d272b1 X-Filterd-Recvd-Size: 5676 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Mon, 2 Nov 2020 15:40:42 +0000 (UTC) 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 202C12222B; Mon, 2 Nov 2020 15:40:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604331641; bh=JULj2YQjQ3lL8L8mphnth/XMQ+6I1NJ7oIH3/fDK0iU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=n0o11Hfll3daQtruT1vsISN+BbHP9yaMYQE4FQMEMibOkJCKqnhjRxA+eho5Laarv OhRwtWZyY8Wy3q5T3/CRffMJ7SInY7t/Bd/Gdm1eHv/y6zMnVypYr0S7YhVNWRGAWn 75tM+sdcYEOnYl8dKrbNCJbF2bUOfaK/T5JUAaOI= Date: Mon, 2 Nov 2020 17:40:28 +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: <20201102154028.GD4879@kernel.org> References: <20200924132904.1391-1-rppt@kernel.org> <20201101110935.GA4105325@laniakea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201101110935.GA4105325@laniakea> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Nov 01, 2020 at 12:09:35PM +0100, Hagen Paul Pfeifer wrote: > * Mike Rapoport | 2020-09-24 16:28:58 [+0300]: > > >This is an implementation of "secret" mappings backed by a file descriptor. > >I've dropped the boot time reservation patch for now as it is not strictly > >required for the basic usage and can be easily added later either with or > >without CMA. > > 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. > 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. > PS: thank you Mike for your effort! > > See the following pseudo-code as an example: > > > // simple assume file-descriptor and mapping is inherited > // by child for simplicity, ptr is > int fd = memfd_secret(SECRETMEM_UNCACHED); > ftruncate(fd, PAGE_SIZE); > uint32_t *ptr = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); The ptr here will be visible to both parent and child. > pid_t pid_other; > > void signal_handler(int sig) > { > // update IPC data on shared, uncachaed, exclusive mapped page > *ptr += 1; > // inform other > sleep(1); > kill(pid_other, SIGUSR1); > } > > void ipc_loop(void) > { > signal(SIGUSR1, signal_handler); > while (1) { > sleep(1); > } > } > > int main(void) > { > pid_t child_pid; > > switch (child_pid = fork()) { > case 0: > pid_other = getppid(); > break; > default: > pid_other = child_pid > break; > } > > ipc_loop(); > } > > > Hagen > -- Sincerely yours, Mike.