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, USER_AGENT_SANE_2 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 E6E14C2D0DB for ; Wed, 22 Jan 2020 14:12:13 +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 BBB7F21734 for ; Wed, 22 Jan 2020 14:12:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BBB7F21734 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42698 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iuGjs-00057u-QK for qemu-devel@archiver.kernel.org; Wed, 22 Jan 2020 09:12:12 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57532) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iuGiw-0003ti-5I for qemu-devel@nongnu.org; Wed, 22 Jan 2020 09:11:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iuGiv-0000ie-2w for qemu-devel@nongnu.org; Wed, 22 Jan 2020 09:11:14 -0500 Received: from 1.mo6.mail-out.ovh.net ([46.105.56.136]:37299) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iuGiu-0000h9-Sg for qemu-devel@nongnu.org; Wed, 22 Jan 2020 09:11:13 -0500 Received: from player738.ha.ovh.net (unknown [10.108.42.168]) by mo6.mail-out.ovh.net (Postfix) with ESMTP id BDA231FAFC1 for ; Wed, 22 Jan 2020 15:11:10 +0100 (CET) Received: from kaod.org (lns-bzn-46-82-253-208-248.adsl.proxad.net [82.253.208.248]) (Authenticated sender: groug@kaod.org) by player738.ha.ovh.net (Postfix) with ESMTPSA id D44F9E9F9F03; Wed, 22 Jan 2020 14:11:08 +0000 (UTC) Date: Wed, 22 Jan 2020 15:11:07 +0100 From: Greg Kurz To: Christian Schoenebeck Subject: Re: [PATCH v4 03/11] 9pfs: validate count sent by client with T_readdir Message-ID: <20200122151107.7b8e5b10@bahia.lan> In-Reply-To: <3990d3891e8ae2074709b56449e96ab4b4b93b7d.1579567020.git.qemu_oss@crudebyte.com> References: <3990d3891e8ae2074709b56449e96ab4b4b93b7d.1579567020.git.qemu_oss@crudebyte.com> X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Ovh-Tracer-Id: 6340505326727108928 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: 0 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedugedrvddtgdehjecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecunecujfgurhepfffhvffukfgjfhfogggtgfesthejredtredtvdenucfhrhhomhepifhrvghgucfmuhhriicuoehgrhhouhhgsehkrghougdrohhrgheqnecukfhppedtrddtrddtrddtpdekvddrvdehfedrvddtkedrvdegkeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhhouggvpehsmhhtphdqohhuthdphhgvlhhopehplhgrhigvrhejfeekrdhhrgdrohhvhhdrnhgvthdpihhnvghtpedtrddtrddtrddtpdhmrghilhhfrhhomhepghhrohhugheskhgrohgurdhorhhgpdhrtghpthhtohepqhgvmhhuqdguvghvvghlsehnohhnghhnuhdrohhrgh X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 46.105.56.136 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: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 21 Jan 2020 00:50:33 +0100 Christian Schoenebeck wrote: > A good 9p client sends T_readdir with "count" parameter that's sufficiently > smaller than client's initially negotiated msize (maximum message size). > We perform a check for that though to avoid the server to be interrupted > with a "Failed to encode VirtFS reply type 41" transport error message by > bad clients. This count value constraint uses msize - 11, because 11 is the > header size of R_readdir. > This would be worth a comment... > Signed-off-by: Christian Schoenebeck > --- > hw/9pfs/9p.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > index a5fbe821d4..18370183c4 100644 > --- a/hw/9pfs/9p.c > +++ b/hw/9pfs/9p.c > @@ -2426,6 +2426,7 @@ static void coroutine_fn v9fs_readdir(void *opaque) > int32_t count; > uint32_t max_count; > V9fsPDU *pdu = opaque; > + V9fsState *s = pdu->s; > > retval = pdu_unmarshal(pdu, offset, "dqd", &fid, > &initial_offset, &max_count); > @@ -2434,6 +2435,13 @@ static void coroutine_fn v9fs_readdir(void *opaque) > } > trace_v9fs_readdir(pdu->tag, pdu->id, fid, initial_offset, max_count); > ... here. Something like: /* Enough space for a R_readdir header: size[4] Rreaddir tag[2] count[4] */ I can fix this in my tree, and actually done so since I've applied patches 1 to 3. Reviewed-by: Greg Kurz > + if (max_count > s->msize - 11) { > + max_count = s->msize - 11; > + warn_report_once( > + "9p: bad client: T_readdir with count > msize - 11" > + ); > + } > + > fidp = get_fid(pdu, fid); > if (fidp == NULL) { > retval = -EINVAL;