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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 A9635C4CEC9 for ; Wed, 18 Sep 2019 20:15:48 +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 7F744218AE for ; Wed, 18 Sep 2019 20:15:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F744218AE 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]:34910 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iAgMd-0005Gy-FX for qemu-devel@archiver.kernel.org; Wed, 18 Sep 2019 16:15:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39356) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iAgLO-0004bK-Jv for qemu-devel@nongnu.org; Wed, 18 Sep 2019 16:14:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iAgLN-0005Ar-Jz for qemu-devel@nongnu.org; Wed, 18 Sep 2019 16:14:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56272) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iAgLJ-00059U-SZ; Wed, 18 Sep 2019 16:14:26 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B885981DE0; Wed, 18 Sep 2019 20:14:24 +0000 (UTC) Received: from [10.10.124.73] (ovpn-124-73.rdu2.redhat.com [10.10.124.73]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7828F5C21A; Wed, 18 Sep 2019 20:14:23 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20190917160731.10895-1-vsementsov@virtuozzo.com> <20190917160731.10895-3-vsementsov@virtuozzo.com> From: John Snow Message-ID: Date: Wed, 18 Sep 2019 16:14:22 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <20190917160731.10895-3-vsementsov@virtuozzo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 18 Sep 2019 20:14:24 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v12 2/2] block/backup: fix backup_cow_with_offload for last cluster 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, den@openvz.org, mreitz@redhat.com, qemu-devel@nongnu.org, qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/17/19 12:07 PM, Vladimir Sementsov-Ogievskiy wrote: > We shouldn't try to copy bytes beyond EOF. Fix it. > > Fixes: 9ded4a0114968e > Signed-off-by: Vladimir Sementsov-Ogievskiy > Reviewed-by: Max Reitz > --- > block/backup.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/backup.c b/block/backup.c > index d8fdbfadfe..89f7f89200 100644 > --- a/block/backup.c > +++ b/block/backup.c > @@ -161,7 +161,7 @@ static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job, > > assert(QEMU_IS_ALIGNED(job->copy_range_size, job->cluster_size)); > assert(QEMU_IS_ALIGNED(start, job->cluster_size)); > - nbytes = MIN(job->copy_range_size, end - start); > + nbytes = MIN(job->copy_range_size, MIN(end, job->len) - start); I'm a little confused. I think the patch as written is correct, but I don't know what problem it solves. If we're going to allow the caller to pass in an end that's beyond EOF, does that mean we are *requiring* the caller to pass in a value that's aligned? We should probably assert what kind of a value we're accepted here, right? We do for start, but should we for 'end' as well? Then ... > nr_clusters = DIV_ROUND_UP(nbytes, job->cluster_size); Don't we just round this right back up immediately anyway? Does that mean we have callers that are passing in an 'end' that's more than 1 job-cluster beyond EOF? That seems like something that should be fixed in the caller, surely? > bdrv_reset_dirty_bitmap(job->copy_bitmap, start, > job->cluster_size * nr_clusters); >