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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 18233CA9EC4 for ; Wed, 30 Oct 2019 08:15:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D1E8F20856 for ; Wed, 30 Oct 2019 08:15:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="FyAYL+pk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1E8F20856 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 806F66B0003; Wed, 30 Oct 2019 04:15:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7DE306B0006; Wed, 30 Oct 2019 04:15:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 71C266B0007; Wed, 30 Oct 2019 04:15:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0103.hostedemail.com [216.40.44.103]) by kanga.kvack.org (Postfix) with ESMTP id 50DE66B0003 for ; Wed, 30 Oct 2019 04:15:40 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id E7C7218DF for ; Wed, 30 Oct 2019 08:15:39 +0000 (UTC) X-FDA: 76099741998.27.horn01_3167a1f122a1b X-HE-Tag: horn01_3167a1f122a1b X-Filterd-Recvd-Size: 3312 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Wed, 30 Oct 2019 08:15:39 +0000 (UTC) Received: from rapoport-lnx (190.228.71.37.rev.sfr.net [37.71.228.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A9CC62067D; Wed, 30 Oct 2019 08:15:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572423338; bh=iS1J5NyS2mmPn50lpxeYWffskvCfVMjwF0kqUnoxyWw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FyAYL+pk/pQmtYM6DFquQE87kHJQ+2nodze4tZvavQE73bdBil7hC7rx+P9j1WuGU JlmZrz8Hf1kfu0trTmrlgRjxU+WoR1EdQemFlorT+lCJKW8ebDw74pSN9GIR0asSfK aPtAhhSUkxoe/pVNW25rZQ0PopjelW+Hk9lv1tBE= Date: Wed, 30 Oct 2019 09:15:30 +0100 From: Mike Rapoport To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Alexey Dobriyan , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Dave Hansen , James Bottomley , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-api@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, Mike Rapoport Subject: Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Message-ID: <20191030081529.GB20624@rapoport-lnx> References: <1572171452-7958-1-git-send-email-rppt@kernel.org> <1572171452-7958-2-git-send-email-rppt@kernel.org> <085ed07e-e646-f7a4-0370-06f33a2a4e4a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <085ed07e-e646-f7a4-0370-06f33a2a4e4a@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) 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 Tue, Oct 29, 2019 at 12:02:34PM +0100, David Hildenbrand wrote: > On 27.10.19 11:17, Mike Rapoport wrote: > >From: Mike Rapoport > > > >The mappings created with MAP_EXCLUSIVE are visible only in the context of > >the owning process and can be used by applications to store secret > >information that will not be visible not only to other processes but to the > >kernel as well. > > > >The pages in these mappings are removed from the kernel direct map and > >marked with PG_user_exclusive flag. When the exclusive area is unmapped, > >the pages are mapped back into the direct map. > > > > Just a thought, the kernel is still able to indirectly read the contents of > these pages by doing a kdump from kexec environment, right? Right. > Also, I wonder > what would happen if you map such pages via /dev/mem into another user space > application and e.g., use them along with kvm [1]. Do you mean that one application creates MAP_EXCLUSIVE and another applications accesses the same physical pages via /dev/mem? With /dev/mem all physical memory is visible... > [1] https://lwn.net/Articles/778240/ > > -- > > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.