From patchwork Mon Aug 26 13:49:57 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13777939 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 5EDBBC5321D for ; Mon, 26 Aug 2024 13:51:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sia7X-0006s1-1D; Mon, 26 Aug 2024 09:50:59 -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 1sia7U-0006oc-Hm for qemu-devel@nongnu.org; Mon, 26 Aug 2024 09:50:56 -0400 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 1sia7R-0007Vw-T5 for qemu-devel@nongnu.org; Mon, 26 Aug 2024 09:50:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1724680252; 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: in-reply-to:in-reply-to:references:references; bh=7oUv5YPGXXDPODp5P6AqXkPQKMLZQw4JZjZpShaJMB4=; b=dWLEZuhkWSAZky9/F7JBQSmfTY4AcZFUwBQjK0SprFWPyq16MMGsl9XkOf1W4KbxGORhTN QBcb2/E8MsjdgwueyWNb1ISmLgySHMUK9r9hjCrpA/fzmGKPJ4H4rM9FvE1ThCdWuZx7TH Mx51FptTVziZp187tv4/U2zJQkfrATo= 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-322-HRFFPOueM8eCG8uav-L7mQ-1; Mon, 26 Aug 2024 09:50:51 -0400 X-MC-Unique: HRFFPOueM8eCG8uav-L7mQ-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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 0B9A71955D47; Mon, 26 Aug 2024 13:50:50 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.102]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 99AC119560A3; Mon, 26 Aug 2024 13:50:47 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Andrey Drobyshev , Stefan Hajnoczi , Vladimir Sementsov-Ogievskiy , Kevin Wolf , Hanna Reitz , qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PULL 1/1] nbd/server: CVE-2024-7409: Avoid use-after-free when closing server Date: Mon, 26 Aug 2024 08:49:57 -0500 Message-ID: <20240826135044.1692814-4-eblake@redhat.com> In-Reply-To: <20240826135044.1692814-3-eblake@redhat.com> References: <20240826135044.1692814-3-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , 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 Message-ID: <20240822143617.800419-2-eblake@redhat.com> 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);