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[2604:1380:1000:8100::1]) by mx.google.com with ESMTPS id x1si5088451pgj.623.2021.11.03.10.43.01 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Nov 2021 10:43:02 -0700 (PDT) Received-SPF: pass (google.com: domain of mptcp+bounces-2354-wpasupplicant.patchew=gmail.com@lists.linux.dev designates 2604:1380:1000:8100::1 as permitted sender) client-ip=2604:1380:1000:8100::1; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=cbG2P6XV; spf=pass (google.com: domain of mptcp+bounces-2354-wpasupplicant.patchew=gmail.com@lists.linux.dev designates 2604:1380:1000:8100::1 as permitted sender) smtp.mailfrom="mptcp+bounces-2354-wpasupplicant.patchew=gmail.com@lists.linux.dev"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sjc.edge.kernel.org (Postfix) with ESMTPS id 80EE03E0F6D for ; Wed, 3 Nov 2021 17:43:01 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9CAFF2C9A; Wed, 3 Nov 2021 17:43:00 +0000 (UTC) X-Original-To: mptcp@lists.linux.dev Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 578F72C98 for ; Wed, 3 Nov 2021 17:42:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635961377; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=q5PS9Xot1aGC0oE41fMYmTmdBkde45aIIIn6WNtLgnQ=; b=cbG2P6XVoFjpidCCd5qT2M+k7Y6xy5p7v0a0qU0O/1tizA/k3YtR099chMkPmmIefEK1yi K7bkcmacToReTrXem3rLgparNRSHyMgWMFr/i6EjZNddsll3g/cR7jLjffmUq2pM0W1ULj +EpqdCecy13HL9Yz+BVR9nYeZkAa9c0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-155-DW5crJgyN_eCI7ByHI_O6Q-1; Wed, 03 Nov 2021 13:42:52 -0400 X-MC-Unique: DW5crJgyN_eCI7ByHI_O6Q-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0E9458042A8 for ; Wed, 3 Nov 2021 17:42:52 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.39.195.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6CFE460843 for ; Wed, 3 Nov 2021 17:42:51 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Subject: [PATCH mptcp-net] mptcp: fix race between close() and accept() Date: Wed, 3 Nov 2021 18:42:47 +0100 Message-Id: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pabeni@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The current implementation of mptcp_accept() is prone to the following race vs mptcp_close(): (on CPU 0) listen(msk) accept(msk) |-> mptcp_stream_accept(msk) |-> (preempted or on CPU 1) close(msk) |-> sk_state =3D TCP_CLOSE, ssk is orphaned, ssk state is unchanged> (preempted or on CPU 0, continuing accept()) |-> mptcp_accept() |-> inet_csk_accept() |-> The solution is atomically close the listener subflow at mptcp_close() time. Reported-by: Mat Martineau Fixes: e16163b6e2b7 ("mptcp: refactor shutdown and close") Signed-off-by: Paolo Abeni --- Note: this should close: https://github.com/multipath-tcp/mptcp_net-next/issues/239 but without a repro I can't be sure... --- net/mptcp/protocol.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 1ee3530ac2a3..4c96a9eb2142 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2712,18 +2712,25 @@ static void mptcp_close(struct sock *sk, long timeo= ut) lock_sock(sk); sk->sk_shutdown =3D SHUTDOWN_MASK; =20 - if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) { - inet_sk_state_store(sk, TCP_CLOSE); + if (sk->sk_state =3D=3D TCP_LISTEN) { + struct socket *listener; + + listener =3D __mptcp_nmpc_socket(mptcp_sk(sk)); + if (listener) + __mptcp_close_ssk(sk, listener->sk, mptcp_subflow_ctx(listener->sk)); goto cleanup; } =20 + if (sk->sk_state =3D=3D TCP_CLOSE) + goto cleanup; + if (mptcp_close_state(sk)) __mptcp_wr_shutdown(sk); =20 sk_stream_wait_close(sk, timeout); =20 cleanup: - /* orphan all the subflows */ + /* orphan all the non listener subflows */ inet_csk(sk)->icsk_mtup.probe_timestamp =3D tcp_jiffies32; mptcp_for_each_subflow(mptcp_sk(sk), subflow) { struct sock *ssk =3D mptcp_subflow_tcp_sock(subflow); --=20 2.26.3