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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D501C433EF for ; Wed, 10 Nov 2021 11:37:18 +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 B309260F5A for ; Wed, 10 Nov 2021 11:37:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B309260F5A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:42770 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mklum-0008I5-Te for qemu-devel@archiver.kernel.org; Wed, 10 Nov 2021 06:37:16 -0500 Received: from eggs.gnu.org ([209.51.188.92]:55758) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mklu0-0007RC-6l for qemu-devel@nongnu.org; Wed, 10 Nov 2021 06:36:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:27382) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mkltw-0007zW-J8 for qemu-devel@nongnu.org; Wed, 10 Nov 2021 06:36:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636544183; 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: in-reply-to:in-reply-to:references:references; bh=77WUx4roxViNtrFIQRMtwmiMrPZhVAvV6MXWqt0uh0I=; b=fdjfDf9JWrU12wq34SE5250szr/kEOyiM5xcWpHPOT44ojDchXqXbscPBLCPvswAqOe9zf 2RhPSVz1plamigx1e2HD+/i20gZSI7lB7T4FQgs6viQ+gEDHRD+vaLKrieieNzlcutR+zL 7z3JJWHPMUmgx3CvH7KFxYWU4wu+r7s= 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-170-ZZbEqrqiN7af5IFRHYMylg-1; Wed, 10 Nov 2021 06:36:20 -0500 X-MC-Unique: ZZbEqrqiN7af5IFRHYMylg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4056A19067E6; Wed, 10 Nov 2021 11:36:19 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.237]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 202CD5D9DE; Wed, 10 Nov 2021 11:36:17 +0000 (UTC) Date: Wed, 10 Nov 2021 12:36:16 +0100 From: Kevin Wolf To: Peter Maydell Subject: Re: qemu-img.c possibly overflowing shifts by BDRV_SECTOR_BITS Message-ID: References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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=us-ascii Content-Disposition: inline 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, 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_H2=-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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Hanna Reitz , QEMU Developers , Qemu-block Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 09.11.2021 um 20:07 hat Peter Maydell geschrieben: > Hi; Coverity is complaining about some of the places in qemu-img.c > where it takes a 32-bit variable and shifts it left by BDRV_SECTOR_BITS > to convert a sector count to a byte count, because it's doing the > shift in 32-bits rather than 64 and so Coverity thinks there might > be overflow (CID 1465221, 1465219). Is it right and we need extra > casts to force the shift to be done in 64 bits, or is there some > constraint that means we know the sector counts are always small > enough that the byte count is 2GB or less ? These are false positives. n is limited to BDRV_REQUEST_MAX_SECTORS already when it starts out in convert_iteration_sectors() (which is enough to make the calculation safe), but for the specific code path, I think it's even guaranteed to be further limited to s->buf_sectors which is 16 MB at most (MAX_BUF_SECTORS in qemu-img.c). Kevin