From nobody Fri Sep 25 10:03:25 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 092F12E0B5C; Sat, 19 Sep 2026 20:40:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789850417; cv=none; b=Jcnb+D5f1udsuvyv+cBZa7ygI4Kwfjg443aPtfiI87Ft4LeKzcVpIiQ9IZUAeZkG+zhW5Yp7HLzQNkl+oFhJcdcgLyKQwwmjoWWy1Zxxdh06sozdWobpJzN6RFOZOxCNEUu6sAxRqJMyBr9d/SkYAaTS+d6vL3BqjZ5Zb3CcU5o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789850417; c=relaxed/simple; bh=ET+0iOGOqPpVPKE5P0X3fT7+cAJZuDccHOJgI+Kfgd0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RatOpd9W8eQnJaKIImcfnMTFEtZMJnIVwndbT4UHcGsWihGuLcelEPr5LDtruXyduX6b4YjPVF/NYTjkH7asbsfrvl6RVs8QHshXUzr/o/eu9M8/Ga/TYVbEZA/BoYIFt8wjYp8bWhrBPtXf9Hb/ts3h7Ly8wZOo3OkaConp14Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fBSwlzvB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fBSwlzvB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 119D71F00899; Sat, 19 Sep 2026 20:40:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789850415; bh=8uwkxK3VPQyQs+d2+4+P1xYmZUb/w2JAsx6JTe7d+TE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fBSwlzvBt3tB9EfFBFPKFgAKkM6zuNt5X26gM1UC9AVB7I3Iw3XsSsX4YJr09s3OI zn7Xrn6Nq+bR2lHbKx1+eqyvbJzYbYbWTSEiKgDy8UPE30mj5gT6c7hIgDpJ/6jCxM WCeA9ktJ11BUNkZzsqY2Ax5Wi/DFyX5GeUJajQz/2x/6nGF+7DJ/hCHZBNz2Hh+imp 0rQpKCXGVDvsyD7ITdGahOb1tAZE9yALmfiAokNo2wFiy+f61uwOMPy3ujtLvFBX/2 8QPiZFLvJfzhbbwo6oOTfWDwSvb7iiN16GTdu9EKqmhOo8Be6unii5FFNCzM29TdmS FTBE1X+WaLjGA== From: "Matthieu Baerts (NGI0)" To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: Florian Westphal , sashal@kernel.org, Matthieu Baerts , Mat Martineau , Jakub Kicinski , "Matthieu Baerts (NGI0)" Subject: [PATCH 5.10.y 1/3] mptcp: hold mptcp socket before calling tcp_done Date: Sat, 19 Sep 2026 22:40:04 +0200 Message-ID: <20260919204002.2106015-6-matttbe@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260919204002.2106015-5-matttbe@kernel.org> References: <20260919204002.2106015-5-matttbe@kernel.org> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1686; i=matttbe@kernel.org; h=from:subject; bh=hwPSCI3l/mXUcDu9zOApkdd3oQgvKAX8zTBIfvs/ZjM=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGLLWfVZ5vTF+9sIJafWfDG4tDhQ/emeGkdsS75ULzZhPL zW0bp6f11HKwiDGxSArpsgi3RaZP/N5FW+Jl58FzBxWJpAhDFycAjAR+WkM/+y1DmZfYwkx6TxS Id5ttUmpUvmQnaS8/Bpe5h1vcqNuizP8M7tpWbzf8kha1EPWbZabv7h03ax48y9OY9YZH/M51S3 mrAA= X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Florian Westphal commit ab82e996a1fa1b9ae514fa357d9ce8df62321157 upstream. When processing options from tcp reset path its possible that tcp_done(ssk) drops the last reference on the mptcp socket which results in use-after-free. Reviewed-by: Matthieu Baerts Signed-off-by: Florian Westphal Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski Stable-dep-of: 2b0f561f21b2 ("mptcp: avoid unneeded actions on subflow rese= t") [ Conflicts in subflow.c, because commit 3ba14528684f ("mptcp: avoid setting TCP_CLOSE state twice") has already been backported and also had the same conflict: this commit here should have been backported first. Fixed now! ] Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/subflow.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index c9cf0fdbfbdc..77cc4f585cd8 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -279,11 +279,16 @@ void mptcp_subflow_reset(struct sock *ssk) struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); struct sock *sk =3D subflow->conn; =20 + /* must hold: tcp_done() could drop last reference on parent */ + sock_hold(sk); + tcp_send_active_reset(ssk, GFP_ATOMIC); tcp_done(ssk); if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) && schedule_work(&mptcp_sk(sk)->work)) - sock_hold(sk); + return; /* worker will put sk for us */ + + sock_put(sk); } =20 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *= skb) --=20 2.55.0 From nobody Fri Sep 25 10:03:25 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F31D42E0B5C; Sat, 19 Sep 2026 20:40:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789850419; cv=none; b=oWmsbZwp/Tru7Dl/8+GOlftAlP0jM6VhXNOulkku9MFMBfmOMB/WVa19QNCUTeDvJ21tt4oOm4nz+SMNM1gcMFIawYx0VGK6Reirj31n28nGAtjl64UpQnJEYMagHDqxYaz3lXm5hwl5Q9gIGubRweFY48tk9OuS0aCORaVWGko= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789850419; c=relaxed/simple; bh=sQCW8mP4OHAWhhTSYZUlL7b0AmGSNQs41XXQWhvl0eg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Na5Ao2MhGF5rGQmCG0BHTkpiteES4VbsIIUJtfMHDCoqVgZ8gaMRg/svT0eAlsdP0vY1X7OmQBLQAV1/cOKDRmJSZYltHbZTZu5Mrnv368XzvrZc+YMjCcl9pWycs4cKlWfu+krGQCmn+OMaZ5M5+4FPFtt19NxQ/LwNfFT2mBM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BZ9zFCWD; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BZ9zFCWD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D9491F000FF; Sat, 19 Sep 2026 20:40:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789850417; bh=X8E/4Wn+iTkDgeZlkfMaj5YPGAO+ob0mPalB++f/HwA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BZ9zFCWDuvgoKyXbZ7DIKXCauBHHKd6WaouqmD6+r8s4TWZbPTtX/NyiYpjs3PLUX Gaog6zorf/QFaJkXaNOjmcKCICDcGSoBwzJFH3i0fum6Yim6/U73yZpLNdH59vFoov UCCh10O+BRfGW1e3lZCtX7nFQgs4M0UTGh7s1GaJ/hhf7YEAZN+gK6qFNvsBXdz4nV 8s5umg2aThjKNZR3Z+KcjAMeaAc5MwQb1B9fEw2m+gp+X7tRwUjFcbXf+p7tUxVymC PjDCQz4uxdZGEinV8ZZ+wHPQlGLokb0plukSYJNGEomfHxfANIQrKKDKr6WrLqoB2d 7pwq1lBMexXHA== From: "Matthieu Baerts (NGI0)" To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: Paolo Abeni , sashal@kernel.org, Xinyang Ge , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 5.10.y 2/3] mptcp: avoid unneeded actions on subflow reset Date: Sat, 19 Sep 2026 22:40:05 +0200 Message-ID: <20260919204002.2106015-7-matttbe@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260919204002.2106015-5-matttbe@kernel.org> References: <20260919204002.2106015-5-matttbe@kernel.org> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4794; i=matttbe@kernel.org; h=from:subject; bh=lqSDkdlltO5bXEZCcYQ+P8vdMPJMl1bzFcLjBpwtQlI=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGLLWfVatu8/7JvVDWZ64p/CNxGUm7wLa57Za/li/y9Agf FFXwoaijlIWBjEuBlkxRRbptsj8mc+reEu8/Cxg5rAygQxh4OIUgInYTmb4p/2g+iXb50vT1Z5P 6hdrO67y4NXas4Ghj2+ob7o+5YzD7hOMDHv0Lha6LeLJs1/VdTRagS/7xe2ImH16k1S4/15Yvf7 HE14A X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Paolo Abeni commit 2b0f561f21b27c40c91ea4975268a06092bd7e9c upstream. Once in a blue moon, the mptcp receive path can recursively call mptcp_data_ready() via state change under unlucky error conditions, and then try to hold the data lock again. Break the recursion loop explicitly checking for the exceptional condition. Add a new flag instead of using an existing one like 'closing', to exit early in subflow_state_change(), and explicitly flush the RX queue at reset time. This avoids unneeded processing to check for available data -- calling get_mapping_status() and more on a dying subflow -- but also in error reporting and worker scheduling. Note that we must consume the currently peeked skb before invoking mptcp_dss_corruption to avoid consuming it again after the eventual reset has freed it. Fixes: e32d262c89e2 ("mptcp: handle consistently DSS corruption") Cc: stable@vger.kernel.org Reported-by: Xinyang Ge Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-1-0= cf5c72667c8@kernel.org Signed-off-by: Jakub Kicinski [ Note: conflict in protocol.c, because commit e0ca4057e0ec ("mptcp: micro-optimize __mptcp_move_skb()") is not in this version, and is part of a consequent rx path refactor. The conflict is in the context, and is easy to resolve, "done =3D true" can be moved along without consequences. Also, the context is slightly different because there is no DEBUG_NET_WARN_ON_ONCE in this version, see the backport commit 12c1676d598e ("mptcp: handle consistently DSS corruption"). Also a conflict in protocol.h, because __unused is at a different number. Decrement the one from this version and add the new flag above. The context is also a bit different with data_avail being an enum, but that's without consequences here. Also a conflict in subflow.c, because commit 71154bbe4942 ("mptcp: fallback earlier on simult connection") was not needed in this version, and cause conflicts in the context, but that's without consequences here. Also, a conflict in the context, because commit 81c1d0290160 ("mptcp: consolidate fallback and non fallback state machine") was not needed in this version. ] Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/protocol.c | 6 +++--- net/mptcp/protocol.h | 3 ++- net/mptcp/subflow.c | 11 +++++++++++ 3 files changed, 16 insertions(+), 4 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 2c6aef813473..292c21713eb7 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -581,11 +581,11 @@ static bool __mptcp_move_skbs_from_subflow(struct mpt= cp_sock *msk, if (unlikely(map_remaining < len)) mptcp_dss_corruption(msk, ssk); } else { - if (unlikely(!fin)) - mptcp_dss_corruption(msk, ssk); - sk_eat_skb(ssk, skb); done =3D true; + + if (unlikely(!fin)) + mptcp_dss_corruption(msk, ssk); } =20 WRITE_ONCE(tp->copied_seq, seq); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index ac064c44079d..b64a50b22d62 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -314,7 +314,8 @@ struct mptcp_subflow_context { mpc_map : 1, backup : 1, rx_eof : 1, - can_ack : 1; /* only after processing the remote a key */ + can_ack : 1, /* only after processing the remote a key */ + resetting : 1; /* subflow is resetting */ enum mptcp_data_avail data_avail; u32 remote_nonce; u64 thmac; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 77cc4f585cd8..fff70a5b06db 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -282,6 +282,10 @@ void mptcp_subflow_reset(struct sock *ssk) /* must hold: tcp_done() could drop last reference on parent */ sock_hold(sk); =20 + subflow->resetting =3D 1; + + /* No need to delay the actual close for to-be discarded data. */ + __skb_queue_purge(&ssk->sk_receive_queue); tcp_send_active_reset(ssk, GFP_ATOMIC); tcp_done(ssk); if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) && @@ -1302,6 +1306,13 @@ static void subflow_state_change(struct sock *sk) =20 __subflow_state_change(sk); =20 + /* Rx queue processing is unneeded, error reporting will take place at + * __mptcp_close_ssk() time and subflow reset can't happen in case of + * fallback: subflow_sched_work_if_closed() would be a no-op. + */ + if (subflow->resetting) + return; + if (subflow_simultaneous_connect(sk)) { mptcp_do_fallback(sk); mptcp_rcv_space_init(mptcp_sk(parent), sk); --=20 2.55.0 From nobody Fri Sep 25 10:03:25 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2525C2E0B5C; Sat, 19 Sep 2026 20:40:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789850421; cv=none; b=H4nj51e2hd+/OuXF4sibL7O+xryRHHXcoMAgDJ6A9Hg1IiK3R1mH34GSN2ulvLcVY60fXxHvhzde/H6iFFtzlecZBqZ7TYm2/dJ9JLFcFBjRWvtWA4op9WOHlVU3cKlRFDqh4BR4109GEzHQS5M+AfkEMMlQojleXkYD7LuZwTE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789850421; c=relaxed/simple; bh=7Mqhwzy14SxGpSCxgPzS8B1ZTiAqAYuw8Z11BcOTLfA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=slgmpZjqBtI9WKlRj+t5IRrxL62tW4xJsw4GRYacihiA6o8MJKkUr93K6KdbgBsk86Izfg/t1IxQYQ4Qw03VGS/V5lMHj/LKBYtm/3dwG64ik2u5Tmy++O2hw7A4ZGsX45IGU2atgvVev6STHGF90cRhqSUB8Ipwv3ZIbfqhgk8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Stqr7POM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Stqr7POM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 049691F00893; Sat, 19 Sep 2026 20:40:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789850419; bh=FGiN7DZE7SNmGs8mXCCFJxnriRZj+k7YKH0AUKtG4PA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Stqr7POMhRyetoKUWCBwaJPlehWCBoS57VVOGI2OXKICWn0ko+AOVWmDwquh/ZFOu Mw8uJd2q202x5TRi17nhk62Xe5NntEU+NkDlOcORlq1PklEDqr8rpauncCJGnYIkn8 5yMJU3/6rHLpP4uj+3a0qBb+a0Nav2wFDd/ghOF6EEIvXEjV9Vr3YNRDzwqFz2oiAN 2CddJ+PwWYN1QH02bqAs3JO9JXQ7f3Xyz3Vf9zPjHk7YzgqF7UaLXf3rVpGykh9K6W iLrLRCMd5xNdat5FdCfuqE5Af9Fs7HZo5kYicb3zikXh6ME68kodfOOsVKeCn3AS7i DvpylsR1n1VAw== From: "Matthieu Baerts (NGI0)" To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: Paolo Abeni , sashal@kernel.org, Shardul Bankar , Xinyang Ge , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 5.10.y 3/3] mptcp: close race between scheduler and state change Date: Sat, 19 Sep 2026 22:40:06 +0200 Message-ID: <20260919204002.2106015-8-matttbe@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260919204002.2106015-5-matttbe@kernel.org> References: <20260919204002.2106015-5-matttbe@kernel.org> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2004; i=matttbe@kernel.org; h=from:subject; bh=3J0g0H6jWDUocJNJZFyoOd1sBfQi2zLg4TVOF/B6coU=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGLLWfVbTUEjS+rqzcS5z5EvRiC1L22Tl1E+v/7phXsbh4 x92TFXc21HKwiDGxSArpsgi3RaZP/N5FW+Jl58FzBxWJpAhDFycAjCRgjKGf9rBK5b/P3BxxYrY jqCVdkUzupdZPtw8ld3xDaerm7JkuSIjw5KpGs9WaP9cVl9ks+f5jJwL38JXK2z/rrK9SHW//Kb Ku3wA X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Paolo Abeni commit 42064de57fb83231fcc89663a94885f228a1ee53 upstream. The mptcp scheduler may race with subflow sockets state change: data transmission on the selected socket may fail and a later release could try to use mss_now reset to 0 for a divide operation. Address the issue by explicitly checking for the critical scenario. Fixes: c886d70286bf ("mptcp: do not queue data on closed subflows") Cc: stable@vger.kernel.org Reported-by: Shardul Bankar Reported-by: Xinyang Ge Closes: https://lore.kernel.org/20260525194828.1137119-1-shardul.b@mpiricso= ftware.com Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-2-0= cf5c72667c8@kernel.org Signed-off-by: Jakub Kicinski [ Note: moved the mss_now check in previous places before commit d9ca1de8c0cd ("mptcp: move page frag allocation in mptcp_sendmsg()") which is not in this version. ] Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/protocol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 292c21713eb7..fdebc451e23a 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1381,7 +1381,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msgh= dr *msg, size_t len) } =20 mptcp_set_timeout(sk, ssk); - if (copied) { + if (copied && mss_now) { tcp_push(ssk, msg->msg_flags, mss_now, tcp_sk(ssk)->nonagle, size_goal); =20 @@ -1891,7 +1891,7 @@ static void mptcp_worker(struct work_struct *work) if (!mptcp_ext_cache_refill(msk)) break; } - if (copied) { + if (copied && mss_now) { tcp_push(ssk, msg.msg_flags, mss_now, tcp_sk(ssk)->nonagle, size_goal); WRITE_ONCE(msk->allow_infinite_fallback, false); --=20 2.55.0