From patchwork Fri Sep 6 06:54:11 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13793486 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 139F7CE7AE0 for ; Fri, 6 Sep 2024 07:04:27 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1smSw4-0004qg-Ix; Fri, 06 Sep 2024 02:59:12 -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 1smSvH-0007YL-E1; Fri, 06 Sep 2024 02:58:24 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1smSvF-0003bg-L8; Fri, 06 Sep 2024 02:58:23 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 5BB908C25E; Fri, 6 Sep 2024 09:53:14 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id 24002133416; Fri, 6 Sep 2024 09:54:32 +0300 (MSK) Received: (nullmailer pid 43653 invoked by uid 1000); Fri, 06 Sep 2024 06:54:30 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Eric Blake , Andrey Drobyshev , Stefan Hajnoczi , Michael Tokarev Subject: [Stable-8.2.7 41/53] nbd/server: CVE-2024-7409: Avoid use-after-free when closing server Date: Fri, 6 Sep 2024 09:54:11 +0300 Message-Id: <20240906065429.42415-41-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, 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 From: Eric Blake 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 (cherry picked from commit 3874f5f73c441c52f1c699c848d463b0eda01e4c) Signed-off-by: Michael Tokarev diff --git a/blockdev-nbd.c b/blockdev-nbd.c index f73409ae49..b36f41b7c5 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);