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=-8.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 34388C43381 for ; Mon, 8 Feb 2021 11:31:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDBAC64E99 for ; Mon, 8 Feb 2021 11:31:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233349AbhBHLau (ORCPT ); Mon, 8 Feb 2021 06:30:50 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:33410 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233351AbhBHL2R (ORCPT ); Mon, 8 Feb 2021 06:28:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612783609; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=m3dJ61ykrqT6xZ75oELmWT0+ySTJ4cYepjC0Xzb/Htc=; b=ZVS8fy6dU7jsaR0+XLT749YjYsZn6nu13l6fuMvEDi4P/bryvKOhVom9lLGZ7g9l3/x5l4 Wo+Cwa6/a3KbyralreX+SNhL9CMiOCZtaXBst00jZIiEMRDCoNDaAZrZmyiMre7Cwj+/IP z/Hgyf2E8dnLS8fyQAeF+/JeN+HuQ5M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-444-k4r9VghcN_OoP9Gu4wJEeA-1; Mon, 08 Feb 2021 06:26:45 -0500 X-MC-Unique: k4r9VghcN_OoP9Gu4wJEeA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 19E1D107ACED; Mon, 8 Feb 2021 11:26:41 +0000 (UTC) Received: from [10.36.113.240] (ovpn-113-240.ams2.redhat.com [10.36.113.240]) by smtp.corp.redhat.com (Postfix) with ESMTP id AA4511002388; Mon, 8 Feb 2021 11:26:32 +0000 (UTC) Subject: Re: [PATCH v17 08/10] PM: hibernate: disable when there are active secretmem users From: David Hildenbrand To: Michal Hocko Cc: Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , 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, Hagen Paul Pfeifer , Palmer Dabbelt References: <20210208084920.2884-1-rppt@kernel.org> <20210208084920.2884-9-rppt@kernel.org> <38c0cad4-ac55-28e4-81c6-4e0414f0620a@redhat.com> <770690dc-634a-78dd-0772-3aba1a3beba8@redhat.com> <21f4e742-1aab-f8ba-f0e7-40faa6d6c0bb@redhat.com> Organization: Red Hat GmbH Message-ID: <5db6ac46-d4e1-3c68-22a0-94f2ecde8801@redhat.com> Date: Mon, 8 Feb 2021 12:26:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <21f4e742-1aab-f8ba-f0e7-40faa6d6c0bb@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 08.02.21 12:14, David Hildenbrand wrote: > On 08.02.21 12:13, David Hildenbrand wrote: >> On 08.02.21 11:57, Michal Hocko wrote: >>> On Mon 08-02-21 11:53:58, David Hildenbrand wrote: >>>> On 08.02.21 11:51, Michal Hocko wrote: >>>>> On Mon 08-02-21 11:32:11, David Hildenbrand wrote: >>>>>> On 08.02.21 11:18, Michal Hocko wrote: >>>>>>> On Mon 08-02-21 10:49:18, Mike Rapoport wrote: >>>>>>>> From: Mike Rapoport >>>>>>>> >>>>>>>> It is unsafe to allow saving of secretmem areas to the hibernation >>>>>>>> snapshot as they would be visible after the resume and this essentially >>>>>>>> will defeat the purpose of secret memory mappings. >>>>>>>> >>>>>>>> Prevent hibernation whenever there are active secret memory users. >>>>>>> >>>>>>> Does this feature need any special handling? As it is effectivelly >>>>>>> unevictable memory then it should behave the same as other mlock, ramfs >>>>>>> which should already disable hibernation as those cannot be swapped out, >>>>>>> no? >>>>>>> >>>>>> >>>>>> Why should unevictable memory not go to swap when hibernating? We're merely >>>>>> dumping all of our system RAM (including any unmovable allocations) to swap >>>>>> storage and the system is essentially completely halted. >>>>>> >>>>> My understanding is that mlock is never really made visible via swap >>>>> storage. >>>> >>>> "Using swap storage for hibernation" and "swapping at runtime" are two >>>> different things. I might be wrong, though. >>> >>> Well, mlock is certainly used to keep sensitive information, not only to >>> protect from major/minor faults. >>> >> >> I think you're right in theory, the man page mentions "Cryptographic >> security software often handles critical bytes like passwords or secret >> keys as data structures" ... >> >> however, I am not aware of any such swap handling and wasn't able to >> spot it quickly. Let me take a closer look. > > s/swap/hibernate/ My F33 system happily hibernates to disk, even with an application that succeeded in din doing an mlockall(). And it somewhat makes sense. Even my freshly-booted, idle F33 has $ cat /proc/meminfo | grep lock Mlocked: 4860 kB So, stopping to hibernate with mlocked memory would essentially prohibit any modern Linux distro to hibernate ever. -- Thanks, David / dhildenb