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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4BEB9C54EBE for ; Tue, 10 Jan 2023 18:17:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239074AbjAJSRR (ORCPT ); Tue, 10 Jan 2023 13:17:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234713AbjAJSQc (ORCPT ); Tue, 10 Jan 2023 13:16:32 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5532840859 for ; Tue, 10 Jan 2023 10:14:56 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E6E6761852 for ; Tue, 10 Jan 2023 18:14:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBD13C433EF; Tue, 10 Jan 2023 18:14:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673374495; bh=I55RRaJo8CB8Gsjw4Snwb+ITZ5sv/GfIsVsT52D0O5E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EU9xNfLJfQ2+lGRmx9zBxX0EZ1SArAY0knEA7Z+/kYexPX9Pi4rlu31rUg32L0Cg3 O+5O2RmY8U6gPrZptlFkixjzE0dfl9jJGp0DXq3ibrDtNgiJpA7LwyukqUUrapWl5a RLTswJW6znDvp76XNv1oeEmwiHFUXSTzH4RgVubQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Matthieu Baerts , Mat Martineau , Paolo Abeni , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 023/159] mptcp: fix lockdep false positive Date: Tue, 10 Jan 2023 19:02:51 +0100 Message-Id: <20230110180019.045496259@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230110180018.288460217@linuxfoundation.org> References: <20230110180018.288460217@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Paolo Abeni [ Upstream commit fec3adfd754ccc99a7230e8ab9f105b65fb07bcc ] MattB reported a lockdep splat in the mptcp listener code cleanup: WARNING: possible circular locking dependency detected packetdrill/14278 is trying to acquire lock: ffff888017d868f0 ((work_completion)(&msk->work)){+.+.}-{0:0}, at: __flush_work (kernel/workqueue.c:3069) but task is already holding lock: ffff888017d84130 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close (net/mptcp/protocol.c:2973) which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (sk_lock-AF_INET){+.+.}-{0:0}: __lock_acquire (kernel/locking/lockdep.c:5055) lock_acquire (kernel/locking/lockdep.c:466) lock_sock_nested (net/core/sock.c:3463) mptcp_worker (net/mptcp/protocol.c:2614) process_one_work (kernel/workqueue.c:2294) worker_thread (include/linux/list.h:292) kthread (kernel/kthread.c:376) ret_from_fork (arch/x86/entry/entry_64.S:312) -> #0 ((work_completion)(&msk->work)){+.+.}-{0:0}: check_prev_add (kernel/locking/lockdep.c:3098) validate_chain (kernel/locking/lockdep.c:3217) __lock_acquire (kernel/locking/lockdep.c:5055) lock_acquire (kernel/locking/lockdep.c:466) __flush_work (kernel/workqueue.c:3070) __cancel_work_timer (kernel/workqueue.c:3160) mptcp_cancel_work (net/mptcp/protocol.c:2758) mptcp_subflow_queue_clean (net/mptcp/subflow.c:1817) __mptcp_close_ssk (net/mptcp/protocol.c:2363) mptcp_destroy_common (net/mptcp/protocol.c:3170) mptcp_destroy (include/net/sock.h:1495) __mptcp_destroy_sock (net/mptcp/protocol.c:2886) __mptcp_close (net/mptcp/protocol.c:2959) mptcp_close (net/mptcp/protocol.c:2974) inet_release (net/ipv4/af_inet.c:432) __sock_release (net/socket.c:651) sock_close (net/socket.c:1367) __fput (fs/file_table.c:320) task_work_run (kernel/task_work.c:181 (discriminator 1)) exit_to_user_mode_prepare (include/linux/resume_user_mode.h:49) syscall_exit_to_user_mode (kernel/entry/common.c:130) do_syscall_64 (arch/x86/entry/common.c:87) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_INET); lock((work_completion)(&msk->work)); lock(sk_lock-AF_INET); lock((work_completion)(&msk->work)); *** DEADLOCK *** The report is actually a false positive, since the only existing lock nesting is the msk socket lock acquired by the mptcp work. cancel_work_sync() is invoked without the relevant socket lock being held, but under a different (the msk listener) socket lock. We could silence the splat adding a per workqueue dynamic lockdep key, but that looks overkill. Instead just tell lockdep the msk socket lock is not held around cancel_work_sync(). Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/322 Fixes: 30e51b923e43 ("mptcp: fix unreleased socket in accept queue") Reported-by: Matthieu Baerts Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/mptcp/protocol.c | 2 +- net/mptcp/protocol.h | 2 +- net/mptcp/subflow.c | 19 +++++++++++++++++-- 3 files changed, 19 insertions(+), 4 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index e64ea2ca1c7a..e97465f0c667 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2371,7 +2371,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, /* otherwise tcp will dispose of the ssk and subflow ctx */ if (ssk->sk_state == TCP_LISTEN) { tcp_set_state(ssk, TCP_CLOSE); - mptcp_subflow_queue_clean(ssk); + mptcp_subflow_queue_clean(sk, ssk); inet_csk_listen_stop(ssk); } __tcp_close(ssk, 0); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 380bddbc52d4..62e9ff237b6e 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -614,7 +614,7 @@ void mptcp_close_ssk(struct sock *sk, struct sock *ssk, struct mptcp_subflow_context *subflow); void __mptcp_subflow_send_ack(struct sock *ssk); void mptcp_subflow_reset(struct sock *ssk); -void mptcp_subflow_queue_clean(struct sock *ssk); +void mptcp_subflow_queue_clean(struct sock *sk, struct sock *ssk); void mptcp_sock_graft(struct sock *sk, struct socket *parent); struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk); bool __mptcp_close(struct sock *sk, long timeout); diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 613f515fedf0..9d3701fdb293 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1733,7 +1733,7 @@ static void subflow_state_change(struct sock *sk) } } -void mptcp_subflow_queue_clean(struct sock *listener_ssk) +void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk) { struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue; struct mptcp_sock *msk, *next, *head = NULL; @@ -1782,8 +1782,23 @@ void mptcp_subflow_queue_clean(struct sock *listener_ssk) do_cancel_work = __mptcp_close(sk, 0); release_sock(sk); - if (do_cancel_work) + if (do_cancel_work) { + /* lockdep will report a false positive ABBA deadlock + * between cancel_work_sync and the listener socket. + * The involved locks belong to different sockets WRT + * the existing AB chain. + * Using a per socket key is problematic as key + * deregistration requires process context and must be + * performed at socket disposal time, in atomic + * context. + * Just tell lockdep to consider the listener socket + * released here. + */ + mutex_release(&listener_sk->sk_lock.dep_map, _RET_IP_); mptcp_cancel_work(sk); + mutex_acquire(&listener_sk->sk_lock.dep_map, + SINGLE_DEPTH_NESTING, 0, _RET_IP_); + } sock_put(sk); } -- 2.35.1