From patchwork Thu Aug 22 14:35:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13773578 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 03DA8C52D7C for ; Thu, 22 Aug 2024 14:37:40 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sh8vT-0003bO-Dp; Thu, 22 Aug 2024 10:36:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sh8vR-0003ZC-KU for qemu-devel@nongnu.org; Thu, 22 Aug 2024 10:36:33 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sh8vQ-0000Jn-3x for qemu-devel@nongnu.org; Thu, 22 Aug 2024 10:36:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1724337391; 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: content-transfer-encoding:content-transfer-encoding; bh=FixiWQ3cwOxFgkWOuuQBMcavXNUKMBjsxQygjgu1SbY=; b=Vm8kddtvy+M+oWPRhc0PZY3yN73wu2UM4v9bBFEj2rxdl44qBaqPSUzcjpl/aWjJEoFGG4 AQupSX2y/2XEc5EzyAVuftX1pml6187U7i8u+4D+msofDuuQnpge+Q/xZR5JDgEhT7brMF JmPaSd7Q1lejwz2cf8MyAO5YZNX+RUA= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-483-itsr66tRPYqkE0OEe0fdnA-1; Thu, 22 Aug 2024 10:36:25 -0400 X-MC-Unique: itsr66tRPYqkE0OEe0fdnA-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DC1451955BEF; Thu, 22 Aug 2024 14:36:23 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.74]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4109719560A3; Thu, 22 Aug 2024 14:36:19 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, qemu-stable@nongnu.org, kwolf@redhat.com, hreitz@redhat.com, berrange@redhat.com, andrey.drobyshev@virtuozzo.com, alexander.ivanov@virtuozzo.com, den@virtuozzo.com, vsementsov@yandex-team.ru Subject: [PATCH for-9.1] nbd/server: CVE-2024-7409: Avoid use-after-free when closing server Date: Thu, 22 Aug 2024 09:35:29 -0500 Message-ID: <20240822143617.800419-2-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 11 X-Spam_score: 1.1 X-Spam_bar: + X-Spam_report: (1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.144, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Commit 3e7ef738 plugged the use-after-free of the global nbd_server object, but overlooked a use-after-free of nbd_server->listener. Although this race is harder to hit, notice that our shutdown path first drops the reference count of nbd_server->listener, then triggers actions that can result in a pending client reaching the nbd_blockdev_client_closed() callback, which in turn calls qio_net_listener_set_client_func on a potentially stale object. If we know we don't want any more clients to connect, and have already told the listener socket to shut down, then we should not be trying to update the listener socket's associated function. Reproducer: > #!/usr/bin/python3 > > import os > from threading import Thread > > def start_stop(): > while 1: > os.system('virsh qemu-monitor-command VM \'{"execute": "nbd-server-start", +"arguments":{"addr":{"type":"unix","data":{"path":"/tmp/nbd-sock"}}}}\'') > os.system('virsh qemu-monitor-command VM \'{"execute": "nbd-server-stop"}\'') > > def nbd_list(): > while 1: > os.system('/path/to/build/qemu-nbd -L -k /tmp/nbd-sock') > > def test(): > sst = Thread(target=start_stop) > sst.start() > nlt = Thread(target=nbd_list) > nlt.start() > > sst.join() > nlt.join() > > test() Fixes: CVE-2024-7409 Fixes: 3e7ef738c8 ("nbd/server: CVE-2024-7409: Close stray clients at server-stop") CC: qemu-stable@nongnu.org Reported-by: Andrey Drobyshev Signed-off-by: Eric Blake Reviewed-by: Stefan Hajnoczi --- blockdev-nbd.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/blockdev-nbd.c b/blockdev-nbd.c index f73409ae494..b36f41b7c5a 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -92,10 +92,13 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc, static void nbd_update_server_watch(NBDServerData *s) { - if (!s->max_connections || s->connections < s->max_connections) { - qio_net_listener_set_client_func(s->listener, nbd_accept, NULL, NULL); - } else { - qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL); + if (s->listener) { + if (!s->max_connections || s->connections < s->max_connections) { + qio_net_listener_set_client_func(s->listener, nbd_accept, NULL, + NULL); + } else { + qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL); + } } } @@ -113,6 +116,7 @@ static void nbd_server_free(NBDServerData *server) */ qio_net_listener_disconnect(server->listener); object_unref(OBJECT(server->listener)); + server->listener = NULL; QLIST_FOREACH_SAFE(conn, &server->conns, next, tmp) { qio_channel_shutdown(QIO_CHANNEL(conn->cioc), QIO_CHANNEL_SHUTDOWN_BOTH, NULL);