From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4CF1C606A320 for ; Tue, 10 Nov 2026 16:20:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Qs7zuFjr Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xQoZD-0004p9-De; Tue, 10 Nov 2026 11:19:27 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xQoZ3-0004mi-6Z for qemu-devel@nongnu.org; Tue, 10 Nov 2026 11:19:22 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xQoZ0-0003h5-9P for qemu-devel@nongnu.org; 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Tue, 10 Nov 2026 16:19:07 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 06BE430000E7; Tue, 10 Nov 2026 16:19:05 +0000 (UTC) Date: Tue, 10 Nov 2026 16:19:03 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, qemu-stable@nongnu.org, stefanha@redhat.com, Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH v3 5/6] nbd/server: Reject rather than assert on non-compliant NBD_OPT_SET_META_CONTEXT Message-ID: References: <20261110153121.1516536-8-eblake@redhat.com> <20261110155356.1520433-7-eblake@redhat.com> <20261110155356.1520433-11-eblake@redhat.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20261110155356.1520433-11-eblake@redhat.com> User-Agent: Mutt/2.4.3 (2026-10-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-22.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Nov 10, 2026 at 09:54:01AM -0600, Eric Blake wrote: > The NBD protocol says that NBD_OPT_{LIST,SET}_META_CONTEXT sends > several lengths that must be consistent: an overall option reply > length, then a series of smaller lengths/data pairs representing the > export name and zero or more context names. If the smaller lengths > within the payload do not add up to the larger value, the client has > sent garbage bytes that will trigger the server's parse of the > client's next option to be out of sync. However, QEMU was dying with > an assertion failure rather than diagnosing the issue, which a > malicious client can then exploit to mount a denial-of-service attack > against QEMU as the NBD server. > > As with several other recent NBD protocol violations, the likelihood > of this attack can be reduced by using TLS and x509 certs to reject > unwanted clients (a "trusted" client can still trigger the problem, > but you first have to compromise the trusted client into sending > arbitrary traffic). > > Fixes: CVE-2026-125683 > Fixes: e7b1948d51 ("nbd: BLOCK_STATUS for standard get_block_status function: server part", v2.12.0) > Reported-by: TonySD via https://gitlab.com/qemu-project/qemu/-/work_items/4843 > CC: qemu-stable@nongnu.org > Signed-off-by: Eric Blake > --- > nbd/server.c | 5 +++++ > 1 file changed, 5 insertions(+) Reviewed-by: Daniel P. Berrangé With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|