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 D3CEFC2D0A3 for ; Wed, 4 Nov 2020 17:03:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F9C12074B for ; Wed, 4 Nov 2020 17:03:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604509393; bh=rNITg8eagPnFNzCzxObVDyyyLvNDMpMqrDKWRtXNo1Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=dTXphvpcKd0K85lgznOJETcYxgMg3bEG9e2a1VyJRtxVjwVp6mZuq6X+PVKeWTTVC YzOvZggkRDzPoQkZSIvTkXDvyzUg2FJqosTnkx5JxhyHx03HFwxtALWwRAtr7yZFU7 YZPB9dpDJIBPoN0XRZo5ZabXpdQSbRwgSXwH6dRk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731590AbgKDRDG (ORCPT ); Wed, 4 Nov 2020 12:03:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:54018 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732031AbgKDRDF (ORCPT ); Wed, 4 Nov 2020 12:03:05 -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 8FD9C2071A; Wed, 4 Nov 2020 17:02:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604509384; bh=rNITg8eagPnFNzCzxObVDyyyLvNDMpMqrDKWRtXNo1Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cbMszixDY/CCQ4Uoej0yke6wNx2huYgP8NhaGqEXUCQOQ+71BtRjL4UN747/oLhHT jlOUbEPtbSsAUpPtJ4TKfNUm3RxZ3UFt+v7azAmQtFc9r46TIiMsgPqIFvZ1tNT9dj lpdbGPMmI1FpQwRmAzKJsAvG+FlUBcvCqAD3nWrU= Date: Wed, 4 Nov 2020 19:02:47 +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: <20201104170247.GT4879@kernel.org> References: <20200924132904.1391-1-rppt@kernel.org> <20201101110935.GA4105325@laniakea> <20201102154028.GD4879@kernel.org> <1547601988.128687.1604411534845@office.mailbox.org> <20201103163002.GK4879@kernel.org> <1988407921.138656.1604489953944@office.mailbox.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1988407921.138656.1604489953944@office.mailbox.org> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, Nov 04, 2020 at 12:39:13PM +0100, Hagen Paul Pfeifer wrote: > > On 11/03/2020 5:30 PM Mike Rapoport wrote: > > > > > > 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. > > A hypothetical "dbus-daemon-secure" service will not be *process related* with communication > peers. E.g. a password-input process (reading a password into secured-memory page) will > transfer the password to dbus-daemon-secure and this service will hand-over the password to > two additional applications: a IPsec process on CPU0 und CPU1 (which itself use a > secured-memory page). > > So four applications IPC chain: > password-input -> dbus-daemon-secure -> {IPsec0, IPsec1} > > - password-input: uses a secured page to read/save the password locally after reading from TTY > - dbus-daemon-secure: uses a secured page for IPC (legitimate user can write and read into the secured page) > - IPSecN has secured page to save the password locally (and probably other data as well), IPC memory is memset'ed after copy > > Goal: the whole password is never saved/touched on non secured pages during IPC transfer. > > Question: maybe a *file-descriptor passing* mechanism can do the trick? I.e. dbus-daemon-secure > allocates via memfd_secret/mmap secure pages and permitted processes will get the descriptor/mmaped-page > passed so they can use the pages directly? Yes, this will work. The processes that share the memfd_secret file descriptor will have access to the same memory pages, pretty much like with shared memory. > Hagen -- Sincerely yours, Mike.