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 610CAECAAD5 for ; Tue, 6 Sep 2022 12:39:46 +0000 (UTC) Received: from localhost ([::1]:52876 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oVXrl-0004nk-Co for qemu-devel@archiver.kernel.org; Tue, 06 Sep 2022 08:39:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39248) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oVWBY-0003Xb-7v for qemu-devel@nongnu.org; Tue, 06 Sep 2022 06:52:05 -0400 Received: from ams.source.kernel.org ([145.40.68.75]:56676) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oVWBW-0002oa-A9 for qemu-devel@nongnu.org; Tue, 06 Sep 2022 06:52:03 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9E0A8B81630; Tue, 6 Sep 2022 10:51:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53993C433C1; Tue, 6 Sep 2022 10:51:55 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="XKtkOR/q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1662461513; 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=37UFh+rhw1ybvWb0RBntJmUoa1a1ej7qgp8+WtJPZMc=; b=XKtkOR/qOQAwL/lIVqkfwMgD6xg+CCpSA2JxhRzdLut4mZlB+fhRKEoi41UE8Ku2VAQ3WY VjQ3eUGGG+jHikgnnmmJeUJ71NjUCMLDV5xSklFfYXZ4sH6APMdiZvnwQz6WMmpLZ9hOej g6g2D63HM7GrgAd2TNDK6zw0dE9hLHc= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 93d5f7f7 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Tue, 6 Sep 2022 10:51:53 +0000 (UTC) Date: Tue, 6 Sep 2022 12:51:50 +0200 From: "Jason A. Donenfeld" To: "Michael S. Tsirkin" Cc: Gerd Hoffmann , Laurent Vivier , Paolo Bonzini , Peter Maydell , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Richard Henderson , Ard Biesheuvel , QEMU Developers , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Subject: Re: [PATCH v2 1/2] x86: only modify setup_data if the boot protocol indicates safety Message-ID: References: <20220906103657.282785-1-Jason@zx2c4.com> <20220906063954-mutt-send-email-mst@kernel.org> <20220906064500-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=145.40.68.75; envelope-from=SRS0=X/Hh=ZJ=zx2c4.com=Jason@kernel.org; helo=ams.source.kernel.org X-Spam_score_int: -67 X-Spam_score: -6.8 X-Spam_bar: ------ X-Spam_report: (-6.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_HI=-5, 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 Tue, Sep 06, 2022 at 12:46:32PM +0200, Jason A. Donenfeld wrote: > On Tue, Sep 06, 2022 at 06:45:34AM -0400, 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. > > Sure, will do. Actually, I'm wrong. This is already done implicitly below with a huge comment: /* * If we're starting an encrypted VM, it will be OVMF based, which uses the * efi stub for booting and doesn't require any values to be placed in the * kernel header. We therefore don't update the header so the hash of the * kernel on the other side of the fw_cfg interface matches the hash of the * file the user passed in. */ if (!sev_enabled()) { memcpy(setup, header, MIN(sizeof(header), setup_size)); } So I'll remove the SEV bit from this commit. Whoops. Glad you asked about it. Jason