From nobody Thu Nov 27 14:01:13 2025 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 BC8F12222C4 for ; Fri, 14 Nov 2025 09:17:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763111851; cv=none; b=mA8MXLOo+OL4EQ7QEEUk45y207+Ys83LJwjfRxDoOJ1gE+BrHoWDIwiNJyQVk/fD9ox/wqeBNtQ0XczM4crw8OgyAWQ4I5MemHg8Wdf5phUMyJKsnORdaYPjcXjm01WYIqNTg/MErV6lXspTLjkW+Nf2gHamA7KQaDmIiCF5/bk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763111851; c=relaxed/simple; bh=Dzf2juHVl0sVND98n1jH36RCIpOTSCDRhccFFuEKttw=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=T4f/YMMNMn5SwNkMIwhRaXVNfAeFVlo7D/ggrbAboPaN4gjwZOwtDC9xn7pMDhFKW3FbsWTSv+L609BEmDUNyHkpKnb+8Tskddptgz/QSYmqEHL8mNAEWdZ9Qg7HIqnC3gOrNZhi1SDf1fcqeTraM08bcV7DL5Ilat9R7/8tFQo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fu2lrJj0; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fu2lrJj0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763111848; 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: in-reply-to:in-reply-to:references:references; bh=m81cAZhPJdxk55S0XQngQABFt9OZ9/xrFNDTWT5z57o=; b=fu2lrJj0sez1FYkQcmrofUllUcgs6gUsY9v8gPWlc7yT2Gn9Upb5NElBCzMMLaKxUEu8Cf pfLcrkOYV2coYV18hBRuT51wn/Yg/r+I1LVd/dwVAsw1Rc7+nZtUPcxW1vVBSuNYJKBTlN feTrb0ca4PK6xijvZ9K1ktF0DilvkDg= Received: from mx-prod-mc-03.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-97-hbdTincdNu23nDunL7Z8dg-1; Fri, 14 Nov 2025 04:17:26 -0500 X-MC-Unique: hbdTincdNu23nDunL7Z8dg-1 X-Mimecast-MFC-AGG-ID: hbdTincdNu23nDunL7Z8dg_1763111846 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F1C2018AB423 for ; Fri, 14 Nov 2025 09:17:25 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.32.173]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 177721800451 for ; Fri, 14 Nov 2025 09:17:24 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Subject: [PATCH v4 mptcp-next 1/3] mptcp: grafting MPJ subflow earlier Date: Fri, 14 Nov 2025 10:17:12 +0100 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Z_xZ_OP4jdkfYPF0Fkn6jSCstfe7loIbUhXMJoCvf00_1763111846 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" Later patches need to ensure that all MPJ subflows are grafted to the msk socket before accept() completion. Currently the grafting happens under the msk socket lock: potentially at msk release_cb time which make satisfying the above condition a bit tricky. Move the MPJ subflow grafting earlier, under the msk data lock, so that we can use such lock as a synchronization point. Signed-off-by: Paolo Abeni --- v3 -> v4: - clarified it's not a fix - move the graft under the msk socket lock - no need to graft for active subflows --- net/mptcp/protocol.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 78ac8ba80e59..4a4cb9952596 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -933,12 +933,6 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk= , struct sock *ssk) mptcp_subflow_joined(msk, ssk); spin_unlock_bh(&msk->fallback_lock); =20 - /* attach to msk socket only after we are sure we will deal with it - * at close time - */ - if (sk->sk_socket && !ssk->sk_socket) - mptcp_sock_graft(ssk, sk->sk_socket); - mptcp_subflow_ctx(ssk)->subflow_id =3D msk->subflow_id++; mptcp_sockopt_sync_locked(msk, ssk); mptcp_stop_tout_timer(sk); @@ -3760,6 +3754,20 @@ void mptcp_sock_graft(struct sock *sk, struct socket= *parent) write_unlock_bh(&sk->sk_callback_lock); } =20 +/* Can be called without holding the msk socket lock; use the callback lock + * to avoid {READ_,WRITE_}ONCE annotations on sk_socket. + */ +static void mptcp_sock_check_graft(struct sock *sk, struct sock *ssk) +{ + struct socket *sock; + + write_lock_bh(&sk->sk_callback_lock); + sock =3D sk->sk_socket; + write_unlock_bh(&sk->sk_callback_lock); + if (sock) + mptcp_sock_graft(ssk, sock); +} + bool mptcp_finish_join(struct sock *ssk) { struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); @@ -3775,7 +3783,9 @@ bool mptcp_finish_join(struct sock *ssk) return false; } =20 - /* active subflow, already present inside the conn_list */ + /* Active subflow, already present inside the conn_list; is grafted + * either by __mptcp_subflow_connect() or accept. + */ if (!list_empty(&subflow->node)) { spin_lock_bh(&msk->fallback_lock); if (!msk->allow_subflows) { @@ -3802,11 +3812,17 @@ bool mptcp_finish_join(struct sock *ssk) if (ret) { sock_hold(ssk); list_add_tail(&subflow->node, &msk->conn_list); + mptcp_sock_check_graft(parent, ssk); } } else { sock_hold(ssk); list_add_tail(&subflow->node, &msk->join_list); __set_bit(MPTCP_FLUSH_JOIN_LIST, &msk->cb_flags); + + /* In case of later failures, __mptcp_flush_join_list() will + * properly orphan the ssk via mptcp_close_ssk(). + */ + mptcp_sock_check_graft(parent, ssk); } mptcp_data_unlock(parent); =20 --=20 2.51.1