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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6EACDC6FA82 for ; Thu, 8 Sep 2022 11:33:50 +0000 (UTC) Received: from localhost ([::1]:37376 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oWFmz-0002bE-T9 for qemu-devel@archiver.kernel.org; Thu, 08 Sep 2022 07:33:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38372) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oWFjy-00016n-Go for qemu-devel@nongnu.org; Thu, 08 Sep 2022 07:30:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:39745) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oWFjm-0005Kr-MT for qemu-devel@nongnu.org; Thu, 08 Sep 2022 07:30:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1662636625; 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=0rHVOog4GCPvSGZhhcG0onC+OQ+pwwUtQkGhihOeB8Q=; b=iSl1oqm2lsyR2j8ekWFYe+XwbFKc3SxRpuoRRPiqajQOq9DRG0vDdSQkNI733gM61F9j4Z OOBm+nkTQfcDUp6C/d7zaLjS2PQkIHuV27YI7TX34PbxGSvESPxh4dRIGbX1UfjICML4VA b7f02/fmMj5Of9ZT2gjqZHOJq58KwAk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-526-7xe-R9PIMjG617T2Arg4BQ-1; Thu, 08 Sep 2022 07:30:22 -0400 X-MC-Unique: 7xe-R9PIMjG617T2Arg4BQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8C60C811E83; Thu, 8 Sep 2022 11:30:21 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (unknown [10.39.195.1]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 004A52026D4C; Thu, 8 Sep 2022 11:30:18 +0000 (UTC) Subject: Re: [PATCH v2 1/2] x86: only modify setup_data if the boot protocol indicates safety To: =?UTF-8?Q?Daniel_P._Berrang=c3=a9?= , Ard Biesheuvel Cc: "Michael S. Tsirkin" , "Jason A. Donenfeld" , Gerd Hoffmann , Laurent Vivier , Paolo Bonzini , Peter Maydell , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Richard Henderson , QEMU Developers References: <20220906103657.282785-1-Jason@zx2c4.com> <20220906063954-mutt-send-email-mst@kernel.org> <20220906064500-mutt-send-email-mst@kernel.org> From: Laszlo Ersek Message-ID: Date: Thu, 8 Sep 2022 13:30:17 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=lersek@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 09/06/22 13:33, Daniel P. Berrangé wrote: > On Tue, Sep 06, 2022 at 01:14:50PM +0200, Ard Biesheuvel wrote: >> (cc Laszlo) >> >> On Tue, 6 Sept 2022 at 12:45, Michael S. Tsirkin wrote: >>> >>> On Tue, Sep 06, 2022 at 12:43:55PM +0200, Jason A. Donenfeld wrote: >>>> On Tue, Sep 6, 2022 at 12:40 PM Michael S. Tsirkin wrote: >>>>> >>>>> On Tue, Sep 06, 2022 at 12:36:56PM +0200, Jason A. Donenfeld wrote: >>>>>> It's only safe to modify the setup_data pointer on newer kernels where >>>>>> the EFI stub loader will ignore it. So condition setting that offset on >>>>>> the newer boot protocol version. While we're at it, gate this on SEV too. >>>>>> This depends on the kernel commit linked below going upstream. >>>>>> >>>>>> Cc: Gerd Hoffmann >>>>>> Cc: Laurent Vivier >>>>>> Cc: Michael S. Tsirkin >>>>>> Cc: Paolo Bonzini >>>>>> Cc: Peter Maydell >>>>>> Cc: Philippe Mathieu-Daudé >>>>>> Cc: Richard Henderson >>>>>> Cc: Ard Biesheuvel >>>>>> Link: https://lore.kernel.org/linux-efi/20220904165321.1140894-1-Jason@zx2c4.com/ >>>>>> Signed-off-by: Jason A. Donenfeld >>>>> >>>>> BTW what does it have to do with SEV? >>>>> Is this because SEV is not going to trust the data to be random anyway? >>>> >>>> Daniel (now CC'd) pointed out in one of the previous threads that this >>>> breaks SEV, because the image hash changes. >>>> >>>> Jason >>> >>> Oh I see. I'd add a comment maybe and definitely mention this >>> in the commit log. >>> >> >> This does raise the question (as I mentioned before) how things like >> secure boot and measured boot are affected when combined with direct >> kernel boot: AIUI, libvirt uses direct kernel boot at guest >> installation time, and modifying setup_data will corrupt the image >> signature. > > IIUC, qemu already modifies setup_data when using direct kernel boot. > > It put in logic to skip this if SEV is enabled, to avoid interfering > with SEV hashes over the kernel, but there's nothing doing this more > generally for non-SEV cases using UEFI. So potentially use of SecureBoot > may already be impacted when using direct kernel boot. Yes, https://github.com/tianocore/edk2/commit/82808b422617 Laszlo > I haven't formally > tested this myself though. I just saw that earlier versions of this > RNG patch broke SEV hashes and later versions addressed that problem > for SEV when the code was re-arranged. > > With regards, > Daniel >