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 F3AC2C3DA7A for ; Thu, 5 Jan 2023 20:26:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231523AbjAEU0q (ORCPT ); Thu, 5 Jan 2023 15:26:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235010AbjAEU0n (ORCPT ); Thu, 5 Jan 2023 15:26:43 -0500 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B410863D27; Thu, 5 Jan 2023 12:26:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1672950400; x=1704486400; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=IpodKiGodZYdzkYzPa+eM2hg8Z9LUQzK7QLyUXw7ofQ=; b=Xh2+YyzJNbPVjqkxyEfQWm2xbiueTZeI9jL1+Hv8TNDVO3nRkROBAspR 4lJH+5lme7sIQflcnaqDa1cOnG4DitYXdOdDT2M86pE4c2AG8DytuF7OM Z6X/BzAiyiFqgXQaA5XPlYzV4lUYHc+CMTk3ouLfD+zTB8uc8zu4Rfp7q lDCSkoL2ie/mNf5A5bRgR1ylbwY/Ebw8qEKJ0iVLYBBh9w7t8pnid45KT 8bUN6STqPbBECm3pA21kRSYcssj9r90Z31J+CuYGjrKUx1dbgZv8LQSi4 wkIcYS36jMVVW10CnBygKbPr+RFt96a1OZ2DlkMnbNrnMpMz+Y2GL/yhL A==; X-IronPort-AV: E=McAfee;i="6500,9779,10581"; a="302684066" X-IronPort-AV: E=Sophos;i="5.96,303,1665471600"; d="scan'208";a="302684066" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jan 2023 12:26:40 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10581"; a="798039412" X-IronPort-AV: E=Sophos;i="5.96,303,1665471600"; d="scan'208";a="798039412" Received: from bkrishn1-mobl.amr.corp.intel.com ([10.251.16.148]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jan 2023 12:26:39 -0800 Date: Thu, 5 Jan 2023 12:26:29 -0800 (PST) From: Mat Martineau To: Shigeru Yoshida cc: matthieu.baerts@tessares.net, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, dmytro@shytyi.net, netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mptcp: Fix deadlock in mptcp_sendmsg() In-Reply-To: <20230105201205.1087439-1-syoshida@redhat.com> Message-ID: <548fc9cf-b674-f37e-8ff7-9abae0bf15a8@linux.intel.com> References: <20230105201205.1087439-1-syoshida@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 6 Jan 2023, Shigeru Yoshida wrote: > __mptcp_close_ssk() can be called from mptcp_sendmsg() with subflow > socket locked. This can cause a deadlock as below: > > mptcp_sendmsg() > mptcp_sendmsg_fastopen() --> lock ssk > tcp_sendmsg_fastopen() > __inet_stream_connect() > mptcp_disconnect() > mptcp_destroy_common() > __mptcp_close_ssk() --> lock ssk again > > This patch fixes the issue by skipping locking for subflow socket > which is already locked. > Hi Shigeru - I believe this has already been fixed by: 7d803344fdc3 ("mptcp: fix deadlock in fastopen error path") It is in the net repo: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git ...but hasn't been merged to net-next or Linus' tree yet. Jakub said to expect a net PR today, which should get the fix both upstream and in to net-next. Thanks, Mat > Fixes: d98a82a6afc7 ("mptcp: handle defer connect in mptcp_sendmsg") > Signed-off-by: Shigeru Yoshida > --- > net/mptcp/protocol.c | 15 +++++++++------ > net/mptcp/protocol.h | 4 ++-- > 2 files changed, 11 insertions(+), 8 deletions(-) > > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index f6f93957275b..979265f66082 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -1672,9 +1672,9 @@ static int mptcp_sendmsg_fastopen(struct sock *sk, struct sock *ssk, struct msgh > lock_sock(ssk); > msg->msg_flags |= MSG_DONTWAIT; > msk->connect_flags = O_NONBLOCK; > - msk->is_sendmsg = 1; > + msk->sendmsg_locked_sk = ssk; > ret = tcp_sendmsg_fastopen(ssk, msg, copied_syn, len, NULL); > - msk->is_sendmsg = 0; > + msk->sendmsg_locked_sk = NULL; > msg->msg_flags = saved_flags; > release_sock(ssk); > > @@ -2319,7 +2319,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, > if (dispose_it) > list_del(&subflow->node); > > - lock_sock_nested(ssk, SINGLE_DEPTH_NESTING); > + if (msk->sendmsg_locked_sk != ssk) > + lock_sock_nested(ssk, SINGLE_DEPTH_NESTING); > > if (flags & MPTCP_CF_FASTCLOSE) { > /* be sure to force the tcp_disconnect() path, > @@ -2335,7 +2336,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, > tcp_disconnect(ssk, 0); > msk->subflow->state = SS_UNCONNECTED; > mptcp_subflow_ctx_reset(subflow); > - release_sock(ssk); > + if (msk->sendmsg_locked_sk != ssk) > + release_sock(ssk); > > goto out; > } > @@ -2362,7 +2364,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, > /* close acquired an extra ref */ > __sock_put(ssk); > } > - release_sock(ssk); > + if (msk->sendmsg_locked_sk != ssk) > + release_sock(ssk); > > sock_put(ssk); > > @@ -3532,7 +3535,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) > /* if reaching here via the fastopen/sendmsg path, the caller already > * acquired the subflow socket lock, too. > */ > - if (msk->is_sendmsg) > + if (msk->sendmsg_locked_sk) > err = __inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags, 1); > else > err = inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags); > diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h > index 955fb3d88eb3..43afc399e16b 100644 > --- a/net/mptcp/protocol.h > +++ b/net/mptcp/protocol.h > @@ -294,8 +294,7 @@ struct mptcp_sock { > u8 mpc_endpoint_id; > u8 recvmsg_inq:1, > cork:1, > - nodelay:1, > - is_sendmsg:1; > + nodelay:1; > int connect_flags; > struct work_struct work; > struct sk_buff *ooo_last_skb; > @@ -318,6 +317,7 @@ struct mptcp_sock { > u32 setsockopt_seq; > char ca_name[TCP_CA_NAME_MAX]; > struct mptcp_sock *dl_next; > + struct sock *sendmsg_locked_sk; > }; > > #define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock) > -- > 2.39.0 > > -- Mat Martineau Intel