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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE, URIBL_BLOCKED autolearn=ham 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 8B712C4708F for ; Wed, 2 Jun 2021 13:59:32 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 5597C613E4 for ; Wed, 2 Jun 2021 13:59:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5597C613E4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58346 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1loRP9-0006ua-Hj for qemu-devel@archiver.kernel.org; Wed, 02 Jun 2021 09:59:31 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44262) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1loRCl-0002hL-Dn for qemu-devel@nongnu.org; Wed, 02 Jun 2021 09:46:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:40767) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1loRCj-0007X7-2J for qemu-devel@nongnu.org; Wed, 02 Jun 2021 09:46:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622641599; 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=HXp4xsK2COsg/sk8cOxH3Dv6mSNqqIz2BKhEw9890PI=; b=Gi/bmFbl/b1xBv7ycLuMLf0Ay1GkdC5BaE/AKxsvHDsG3ztr6Y2NBDwNRFBPyVgcg5xgfr qNS/amqvZqy4niL/VsPDVxLwy8ohfEXqSQV9xVsJgLCnnWhee9EUj5TPKIAXSMkAS1xwYv 84E1sNaay8YBlDgzU2UMLaQEPTRakLs= 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-60-8lfCwswKPPOobjzalGIpCg-1; Wed, 02 Jun 2021 09:46:36 -0400 X-MC-Unique: 8lfCwswKPPOobjzalGIpCg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7F5111085137; Wed, 2 Jun 2021 13:45:59 +0000 (UTC) Received: from merkur.redhat.com (ovpn-114-240.ams2.redhat.com [10.36.114.240]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8DC2F60BD9; Wed, 2 Jun 2021 13:45:58 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 20/20] docs/secure-coding-practices: Describe how to use 'null-co' block driver Date: Wed, 2 Jun 2021 15:45:29 +0200 Message-Id: <20210602134529.231756-21-kwolf@redhat.com> In-Reply-To: <20210602134529.231756-1-kwolf@redhat.com> References: <20210602134529.231756-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.371, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Philippe Mathieu-Daudé Document that security reports must use 'null-co,read-zeroes=on' because otherwise the memory is left uninitialized (which is an on-purpose performance feature). Reviewed-by: Vladimir Sementsov-Ogievskiy Signed-off-by: Philippe Mathieu-Daudé Message-Id: <20210601162548.2076631-1-philmd@redhat.com> Signed-off-by: Kevin Wolf --- docs/devel/secure-coding-practices.rst | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/docs/devel/secure-coding-practices.rst b/docs/devel/secure-coding-practices.rst index cbfc8af67e..0454cc527e 100644 --- a/docs/devel/secure-coding-practices.rst +++ b/docs/devel/secure-coding-practices.rst @@ -104,3 +104,12 @@ structures and only process the local copy. This prevents time-of-check-to-time-of-use (TOCTOU) race conditions that could cause QEMU to crash when a vCPU thread modifies guest RAM while device emulation is processing it. + +Use of null-co block drivers +---------------------------- + +The ``null-co`` block driver is designed for performance: its read accesses are +not initialized by default. In case this driver has to be used for security +research, it must be used with the ``read-zeroes=on`` option which fills read +buffers with zeroes. Security issues reported with the default +(``read-zeroes=off``) will be discarded. -- 2.30.2