From nobody Mon Feb 9 00:10:49 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 4800E27A44A for ; Fri, 11 Jul 2025 09:30:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752226203; cv=none; b=a1JPhHGvS+lHqsvSVF7Eb/HdcD3+dJFspeK6XBnbvnikvCcHKhYMs+frN9t/mk7QEyXCEwjcINlAi6X8jR4M8QJay94Xd4AKLZk6ZKyf915mF7+n7LF87KnhWtEp72M7hEtOkuwCpr1ruHwfccMy8jstG/Pqg8MmIWRdoEJfaFk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752226203; c=relaxed/simple; bh=b5junekmRqQSUXh7yXxmNWuneIufCOQ1ZmVkDnv7H0c=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=oIEvlBXYerdYSNsh0S9FZrFOyXBOYcS+XYSzvlwbKj8TX6Nm3brnn9S6d4q8f9BuPt5yO6hNEb8YX9hQXSSRUrh92L2Uo/vqkzEmTsNdpldlh1XAXpeX0o1TlVXXlhnhKkJ8KuenjbjMYvt0O8imeKJFV24H/hJe28xv6HIviNg= 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=LTA387kB; arc=none smtp.client-ip=170.10.133.124 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="LTA387kB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1752226200; 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=7vJRda906NWEC2na7hvzJ364+UL7WMLISTn9a7UhzKU=; b=LTA387kB6lV5O2B/6i0V9Zc6BQXtGbF/oHw6GiEXyLVujgGiHk5A3K1Ey7JflCGfF2DeNn P/6+i7WuSOqpIVBBRz53rWOMUrnNdP7SQInBY54uzKhhzsVsjHEftvIJMkBVzItB13J+rd omQXfOeMvgBU6CITtyiGNyHgPWYMxCo= Received: from mx-prod-mc-02.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-680-q-YyRdF5P56dTiDwPWSq0g-1; Fri, 11 Jul 2025 05:29:58 -0400 X-MC-Unique: q-YyRdF5P56dTiDwPWSq0g-1 X-Mimecast-MFC-AGG-ID: q-YyRdF5P56dTiDwPWSq0g_1752226198 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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9AF6E1955EC9 for ; Fri, 11 Jul 2025 09:29:56 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.33.145]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id C030F1800EC8 for ; Fri, 11 Jul 2025 09:29:55 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Subject: [PATCH v4 mptcp-net 2/5] mptcp: plug races between subflow fail and subflow creation Date: Fri, 11 Jul 2025 11:29:42 +0200 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: qrUYClshC4PsvjS8HbvFtB8VwjXVrc8Vax14jhcbKIs_1752226198 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" We have races similar to the one addressed by the previous patch between subflow failing and additional subflow creation. They are just harder to trigger. The solution is similar. Use a separate flag to track the condition 'socket state prevent any additional subflow creation' protected by the fallback lock. The socket fallback makes such flag true, and also receiving or sending a MPTCP fail option. The field 'allow_infinite_fallback' is now always touched under the relevant lock, we can drop the ONCE annotation on write. Fixes: 478d770008b0 ("mptcp: send out MP_FAIL when data checksum fails") Signed-off-by: Paolo Abeni --- net/mptcp/pm.c | 8 +++++++- net/mptcp/protocol.c | 11 ++++++----- net/mptcp/protocol.h | 8 +++++++- net/mptcp/subflow.c | 19 ++++++++++++++----- 4 files changed, 34 insertions(+), 12 deletions(-) diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 25ce2d5135bc..687dbb59d084 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -765,8 +765,14 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fa= il_seq) =20 pr_debug("fail_seq=3D%llu\n", fail_seq); =20 - if (!READ_ONCE(msk->allow_infinite_fallback)) + /* After accepting the fail, we can't create any other subflows */ + spin_lock_bh(&msk->fallback_lock); + if (!msk->allow_infinite_fallback) { + spin_unlock_bh(&msk->fallback_lock); return; + } + msk->allow_subflows =3D false; + spin_unlock_bh(&msk->fallback_lock); =20 if (!subflow->fail_tout) { pr_debug("send MP_FAIL response and infinite map\n"); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 4ddf3a1e0085..49498cdd17f0 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -791,7 +791,7 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk) static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk) { mptcp_subflow_ctx(ssk)->map_seq =3D READ_ONCE(msk->ack_seq); - WRITE_ONCE(msk->allow_infinite_fallback, false); + msk->allow_infinite_fallback =3D false; mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC); } =20 @@ -803,7 +803,7 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk,= struct sock *ssk) return false; =20 spin_lock_bh(&msk->fallback_lock); - if (__mptcp_check_fallback(msk)) { + if (!msk->allow_subflows) { spin_unlock_bh(&msk->fallback_lock); return false; } @@ -2625,7 +2625,7 @@ static void __mptcp_retrans(struct sock *sk) len =3D max(copied, len); tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle, info.size_goal); - WRITE_ONCE(msk->allow_infinite_fallback, false); + msk->allow_infinite_fallback =3D false; } spin_unlock_bh(&msk->fallback_lock); =20 @@ -2753,7 +2753,8 @@ static void __mptcp_init_sock(struct sock *sk) WRITE_ONCE(msk->first, NULL); inet_csk(sk)->icsk_sync_mss =3D mptcp_sync_mss; WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk))); - WRITE_ONCE(msk->allow_infinite_fallback, true); + msk->allow_infinite_fallback =3D true; + msk->allow_subflows =3D true; msk->recovery =3D false; msk->subflow_id =3D 1; msk->last_data_sent =3D tcp_jiffies32; @@ -3549,7 +3550,7 @@ bool mptcp_finish_join(struct sock *ssk) /* active subflow, already present inside the conn_list */ if (!list_empty(&subflow->node)) { spin_lock_bh(&msk->fallback_lock); - if (__mptcp_check_fallback(msk)) { + if (!msk->allow_subflows) { spin_unlock_bh(&msk->fallback_lock); return false; } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 61a9ff467501..c8b4ebe198dc 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -348,11 +348,16 @@ struct mptcp_sock { u64 rtt_us; /* last maximum rtt of subflows */ } rcvq_space; u8 scaling_ratio; + bool allow_subflows; =20 u32 subflow_id; u32 setsockopt_seq; char ca_name[TCP_CA_NAME_MAX]; - spinlock_t fallback_lock; /* protects fallback && allow_infinite_fallback= */ + + spinlock_t fallback_lock; /* protects fallback, + * allow_infinite_fallback and + * allow_join + */ }; =20 #define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock) @@ -1227,6 +1232,7 @@ static inline bool __mptcp_try_fallback(struct mptcp_= sock *msk) return false; } =20 + msk->allow_subflows =3D false; set_bit(MPTCP_FALLBACK_DONE, &msk->flags); spin_unlock_bh(&msk->fallback_lock); return true; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index a6a35985e551..1802bc5435a1 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1302,20 +1302,29 @@ static void subflow_sched_work_if_closed(struct mpt= cp_sock *msk, struct sock *ss mptcp_schedule_work(sk); } =20 -static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) +static bool mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) { struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); unsigned long fail_tout; =20 + /* we are really failing, prevent any later subflow join */ + spin_lock_bh(&msk->fallback_lock); + if (!msk->allow_infinite_fallback) { + spin_unlock_bh(&msk->fallback_lock); + return false; + } + msk->allow_subflows =3D false; + spin_unlock_bh(&msk->fallback_lock); + /* graceful failure can happen only on the MPC subflow */ if (WARN_ON_ONCE(ssk !=3D READ_ONCE(msk->first))) - return; + return false; =20 /* since the close timeout take precedence on the fail one, * no need to start the latter when the first is already set */ if (sock_flag((struct sock *)msk, SOCK_DEAD)) - return; + return true; =20 /* we don't need extreme accuracy here, use a zero fail_tout as special * value meaning no fail timeout at all; @@ -1327,6 +1336,7 @@ static void mptcp_subflow_fail(struct mptcp_sock *msk= , struct sock *ssk) tcp_send_ack(ssk); =20 mptcp_reset_tout_timer(msk, subflow->fail_tout); + return true; } =20 static bool subflow_check_data_avail(struct sock *ssk) @@ -1387,12 +1397,11 @@ static bool subflow_check_data_avail(struct sock *s= sk) (subflow->mp_join || subflow->valid_csum_seen)) { subflow->send_mp_fail =3D 1; =20 - if (!READ_ONCE(msk->allow_infinite_fallback)) { + if (!mptcp_subflow_fail(msk, ssk)) { subflow->reset_transient =3D 0; subflow->reset_reason =3D MPTCP_RST_EMIDDLEBOX; goto reset; } - mptcp_subflow_fail(msk, ssk); WRITE_ONCE(subflow->data_avail, true); return true; } --=20 2.50.0