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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 103BFC3A5A9 for ; Mon, 4 May 2020 14:56:45 +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 CC465206D9 for ; Mon, 4 May 2020 14:56:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AxLpYE1P" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CC465206D9 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]:51124 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jVcWR-00046k-Tu for qemu-devel@archiver.kernel.org; Mon, 04 May 2020 10:56:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51486) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jVcRa-0003AT-KV for qemu-devel@nongnu.org; Mon, 04 May 2020 10:51:42 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:57716 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jVcRZ-0005WG-Rs for qemu-devel@nongnu.org; Mon, 04 May 2020 10:51:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588603901; 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=hrLrQr+R/T9s03X9urIw7MWei7yBJ0eNzyIVI1Vhb1g=; b=AxLpYE1P3ml3VcYi5RUBFU0l1+6WHgSe6aOFlsVhG99g9WGkAzKoZO9u5rpLerr9uVqrB+ 0lL615Kx9VxYMatUEAAo0Ny/xwn3UBIUxavVqGS/guK7jA1uR1gJkD9KCxce10t49IZ12W RgB/UoMyOmZPwjksDGEV01BBu423Td0= 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-278-YgQuK88BMIypfIXmRb35CA-1; Mon, 04 May 2020 10:51:34 -0400 X-MC-Unique: YgQuK88BMIypfIXmRb35CA-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 A79761054F9B; Mon, 4 May 2020 14:51:33 +0000 (UTC) Received: from [10.3.114.73] (ovpn-114-73.phx2.redhat.com [10.3.114.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3EE1A1002389; Mon, 4 May 2020 14:51:33 +0000 (UTC) Subject: Re: [PATCH] qcow2: Avoid integer wraparound in qcow2_co_truncate() To: Alberto Garcia , qemu-devel@nongnu.org References: <20200501131525.6745-1-berto@igalia.com> <5ba91898-9d3b-d55d-c360-83cca41d88f4@redhat.com> <101fcf8e-0352-9151-f25a-c8a38aa079ed@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Mon, 4 May 2020 09:51:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=205.139.110.61; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/04 01:21:32 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: Kevin Wolf , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/4/20 8:47 AM, Alberto Garcia wrote: >> Drop this hunk (leave zero_start unchanged), and instead... >> >>> >>> So, using your numbers, pre-patch, we have zero_start =3D 0x90000 (0x82= 000 >>> rounded up to 0x10000 alignment).=C2=A0 post-patch, the new MIN() lower= s it >>> back to 0x8dc00 (the new size), which is unaligned. >>> >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * Use ze= ro clusters as much as we can. qcow2_cluster_zeroize() >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * requir= es a cluster-aligned start. The end may be >>>> unaligned if it is >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * at the end of the = image (which it is here). >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D qcow2_cluster_zero= ize(bs, zero_start, offset - >>> zero_start, 0); >> >> ...patch _this_ call to compute 'QEMU_ALIGN_UP(offset, s->cluster_size) >> - zero_start' for the length. >=20 > That would work, but then we would be writing zeroes beyond the end of > the image (but still within the last cluster). >=20 > The other solution is to keep my hunk and call qcow2_cluster_zeroize() > only when offset > zero_start. Yes, that would work, and probably less complicated. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org