From nobody Sun Oct 5 19:22:53 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1543616064505305.21805375986446; Fri, 30 Nov 2018 14:14:24 -0800 (PST) Received: from localhost ([::1]:34877 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSr3H-0006iJ-Dy for importer@patchew.org; Fri, 30 Nov 2018 17:14:23 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55956) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSqtI-0004Nx-1C for qemu-devel@nongnu.org; Fri, 30 Nov 2018 17:04:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gSqtG-0004CB-F6 for qemu-devel@nongnu.org; Fri, 30 Nov 2018 17:04:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38174) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gSqtB-0003bJ-U0; Fri, 30 Nov 2018 17:03:58 -0500 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 mx1.redhat.com (Postfix) with ESMTPS id 45C083002887; Fri, 30 Nov 2018 22:03:57 +0000 (UTC) Received: from red.redhat.com (ovpn-117-105.phx2.redhat.com [10.3.117.105]) by smtp.corp.redhat.com (Postfix) with ESMTP id AD7951057072; Fri, 30 Nov 2018 22:03:56 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Date: Fri, 30 Nov 2018 16:03:34 -0600 Message-Id: <20181130220344.3350618-6-eblake@redhat.com> In-Reply-To: <20181130220344.3350618-1-eblake@redhat.com> References: <20181130220344.3350618-1-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Fri, 30 Nov 2018 22:03:57 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 05/14] nbd/client: Drop pointless buf variable X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: nsoffer@redhat.com, vsementsov@virtuozzo.com, jsnow@redhat.com, rjones@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" There's no need to read into a temporary buffer (oversized since commit 7d3123e1) followed by a byteswap into a uint64_t to check for a magic number via memcmp(), when the code immediately below demonstrates reading into the uint64_t then byteswapping in place and checking for a magic number via integer math. What's more, having a different error message when the server's first reply byte is 0 is unusual - it's no different from any other wrong magic number, and we already detected short reads. Signed-off-by: Eric Blake Reviewed-by: Richard W.M. Jones Reviewed-by: Vladimir Sementsov-Ogievskiy --- nbd/nbd-internal.h | 1 + nbd/client.c | 14 +++----------- 2 files changed, 4 insertions(+), 11 deletions(-) diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h index eeff78d3c98..306a533dcd1 100644 --- a/nbd/nbd-internal.h +++ b/nbd/nbd-internal.h @@ -46,6 +46,7 @@ /* Size of oldstyle negotiation */ #define NBD_OLDSTYLE_NEGOTIATE_SIZE (8 + 8 + 8 + 4 + 124) +#define NBD_INIT_MAGIC 0x4e42444d41474943LL #define NBD_REQUEST_MAGIC 0x25609513 #define NBD_OPTS_MAGIC 0x49484156454F5054LL #define NBD_CLIENT_MAGIC 0x0000420281861253LL diff --git a/nbd/client.c b/nbd/client.c index 0be89f9e641..17ee24492a4 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -731,7 +731,6 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *= name, QIOChannel **outioc, NBDExportInfo *info, Error **errp) { - char buf[256]; uint64_t magic; int rc; bool zeroes =3D true; @@ -752,21 +751,14 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char= *name, goto fail; } - if (nbd_read(ioc, buf, 8, errp) < 0) { + if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) { error_prepend(errp, "Failed to read data: "); goto fail; } - - buf[8] =3D '\0'; - if (strlen(buf) =3D=3D 0) { - error_setg(errp, "Server connection closed unexpectedly"); - goto fail; - } - - magic =3D ldq_be_p(buf); + magic =3D be64_to_cpu(magic); trace_nbd_receive_negotiate_magic(magic); - if (memcmp(buf, "NBDMAGIC", 8) !=3D 0) { + if (magic !=3D NBD_INIT_MAGIC) { error_setg(errp, "Invalid magic received"); goto fail; } --=20 2.17.2