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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 1001EC433DB for ; Tue, 26 Jan 2021 07:18:20 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 99E5D22B3F for ; Tue, 26 Jan 2021 07:18:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 99E5D22B3F Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=lh0/KYEsX4i8oMWEtdXqFfJ77VP7lqX44J0/DeIiWss=; b=qQs/XCv2p5BBtaJEMoJlWxB2y CyXkQQW17YZ7eRMVfit3Xn7RRYA9DsHK2+6JpPLB44cqp9ilFf4BceOAA6dOdKD9zEnJ3LsG19aRV ath5jmNR9pmcrCqj/hrtWy6r/o4zK+JJZ/ZHTW9j2Yrcl3QuBysA+Tqd2jJSzMF9wfVvTZ1otb22d ns+XD0XIKo1+uDqwAfXr2q6MBXkEPNNAfYT3hZsdptR6Np6cf3yiQqs+JJ6Gp8cNVnvjOH+bAlJIS W/RtqqDLJZTXwYTY3kCbSeMERoX8DblF6WVp04s5ftRY+xCDa/JJ0nxJsdV9L58utT8k2zUf+vD1n DvbhVknKg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l4IaL-0000dk-GR; Tue, 26 Jan 2021 07:16:21 +0000 Received: from mx2.suse.de ([195.135.220.15]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l4IaI-0000cv-R6; Tue, 26 Jan 2021 07:16:20 +0000 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1611645376; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Rfz4YhgMdQKfWEhdPjTzowRS8ZrfPb0PZUsBEItApiI=; b=uSwnbNJryXqrtFn5ZDcik0uto2+MPvheE1cGTKIEOz6ZnfiLtVVNW3xYyy9RGpwnpMhlvH 1N3K5WJgiIeLyB1+A5OyZuJP2Jkezi6uvJEEzgHe7uQUCBH5hRl4x8iwIwlEA1xmTBtqZQ dR3KQIpKfgXY/BC62Y8U0m9xExJlGg8= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5743EAE91; Tue, 26 Jan 2021 07:16:16 +0000 (UTC) Date: Tue, 26 Jan 2021 08:16:14 +0100 From: Michal Hocko To: Mike Rapoport Subject: Re: [PATCH v16 06/11] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <20210126071614.GX827@dhcp22.suse.cz> References: <20210121122723.3446-1-rppt@kernel.org> <20210121122723.3446-7-rppt@kernel.org> <20210125170122.GU827@dhcp22.suse.cz> <20210125213618.GL6332@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210125213618.GL6332@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210126_021619_111173_714857C8 X-CRM114-Status: GOOD ( 29.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , David Hildenbrand , Peter Zijlstra , Catalin Marinas , Dave Hansen , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, "H. Peter Anvin" , Christopher Lameter , Shuah Khan , Thomas Gleixner , Elena Reshetova , linux-arch@vger.kernel.org, Tycho Andersen , linux-nvdimm@lists.01.org, Will Deacon , x86@kernel.org, Matthew Wilcox , Mike Rapoport , Ingo Molnar , Michael Kerrisk , Palmer Dabbelt , Arnd Bergmann , James Bottomley , Hagen Paul Pfeifer , Borislav Petkov , Alexander Viro , Andy Lutomirski , Paul Walmsley , "Kirill A. Shutemov" , Dan Williams , linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Palmer Dabbelt , linux-fsdevel@vger.kernel.org, Shakeel Butt , Andrew Morton , Rick Edgecombe , Roman Gushchin Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon 25-01-21 23:36:18, Mike Rapoport wrote: > On Mon, Jan 25, 2021 at 06:01:22PM +0100, Michal Hocko wrote: > > On Thu 21-01-21 14:27:18, Mike Rapoport wrote: > > > From: Mike Rapoport > > > > > > Introduce "memfd_secret" system call with the ability to create memory > > > areas visible only in the context of the owning process and not mapped not > > > only to other processes but in the kernel page tables as well. > > > > > > The user will create a file descriptor using the memfd_secret() system > > > call. The memory areas created by mmap() calls from this file descriptor > > > will be unmapped from the kernel direct map and they will be only mapped in > > > the page table of the owning mm. > > > > > > The secret memory remains accessible in the process context using uaccess > > > primitives, but it is not accessible using direct/linear map addresses. > > > > > > Functions in the follow_page()/get_user_page() family will refuse to return > > > a page that belongs to the secret memory area. > > > > > > A page that was a part of the secret memory area is cleared when it is > > > freed. > > > > > > The following example demonstrates creation of a secret mapping (error > > > handling is omitted): > > > > > > fd = memfd_secret(0); > > > ftruncate(fd, MAP_SIZE); > > > ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); > > > > I do not see any access control or permission model for this feature. > > Is this feature generally safe to anybody? > > The mappings obey memlock limit. Besides, this feature should be enabled > explicitly at boot with the kernel parameter that says what is the maximal > memory size secretmem can consume. Why is such a model sufficient and future proof? I mean even when it has to be enabled by an admin it is still all or nothing approach. Mlock limit is not really useful because it is per mm rather than per user. Is there any reason why this is allowed for non-privileged processes? Maybe this has been discussed in the past but is there any reason why this cannot be done by a special device which will allow to provide at least some permission policy? Please make sure to describe all those details in the changelog. -- Michal Hocko SUSE Labs _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel