From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 46C283EDE4B; Tue, 12 May 2026 17:51:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778608281; cv=none; b=rilYHQlrGylhZaOmTBvEuDUJ6aDsJjhfQjN2pCDjV7iovY0dZbvFdtfMfdvi1NPVPUkP0knk/tt8SWWPkLEW1nhav2m7Mwb/Szv2MIJHFVzzh0ngZRpHviuwsG7umXVGAqJUsQeXc4oXaYTIA0HygmdmMk7gCIYUfWvgH+hs0qk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778608281; c=relaxed/simple; bh=r6iGfvEkABTRsQCaOzhJ+9EtOFpe0/NJFhEL5nlRTQw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ge9mHbxIcp7gFvnUfdFwcZJ2c0wI+Z1eR8xZCl8weM5cbOnpSg+xly8J18BC7dzWrreGc6S/v99jr3xKEHMHId/dMvt1umj5lf02dbncd9c3umZfkcWChFLMl5/heHOUSKD7jBh+ZNiqFprPsmBRnNCq6/7O21Zs1wv1++DGDaE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Eo7wZ/VR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Eo7wZ/VR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8CF20C2BCC7; Tue, 12 May 2026 17:51:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778608280; bh=r6iGfvEkABTRsQCaOzhJ+9EtOFpe0/NJFhEL5nlRTQw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Eo7wZ/VR5URPMkOS0IAjEqdIPUZCYoDIttH79EGmofXA6X7KKPP6Vn/S1+mRycMLq 0hsiFr1Y9MoXnlCh80iKlc9XF2EriM/Qw62vAzbyW344ZmwRdezpvJE41QN3WuVO7r AOvTppe/YjEQTtLnjAa4mlliHmR7BFD4ZHwRBxgY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gang Yan , Paolo Abeni , "Matthieu Baerts (NGI0)" , Sasha Levin Subject: [PATCH 6.18 019/270] mptcp: sync the msk->sndbuf at accept() time Date: Tue, 12 May 2026 19:37:00 +0200 Message-ID: <20260512173938.861898101@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260512173938.452574370@linuxfoundation.org> References: <20260512173938.452574370@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gang Yan commit fcf04b14334641f4b0b8647824480935e9416d52 upstream. On passive MPTCP connections, the msk sndbuf is not updated correctly. The root cause is an order issue in the accept path: - tcp_check_req() -> subflow_syn_recv_sock() -> mptcp_sk_clone_init() calls __mptcp_propagate_sndbuf() to copy the ssk sndbuf into msk - Later, tcp_child_process() -> tcp_init_transfer() -> tcp_sndbuf_expand() grows the ssk sndbuf. So __mptcp_propagate_sndbuf() runs before the ssk sndbuf has been expanded and the msk ends up with a much smaller sndbuf than the subflow: MPTCP: msk->sndbuf:20480, msk->first->sndbuf:2626560 Fix this by moving the __mptcp_propagate_sndbuf() call from mptcp_sk_clone_init() -- the ssk sndbuf is not yet finalized there -- to __mptcp_propagate_sndbuf() at accept() time, when the ssk sndbuf has been fully expanded by tcp_sndbuf_expand(). Fixes: 8005184fd1ca ("mptcp: refactor sndbuf auto-tuning") Cc: stable@vger.kernel.org Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/602 Signed-off-by: Gang Yan Acked-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260420-net-mptcp-sync-sndbuf-accept-v1-1-e3523e3aeb44@kernel.org Signed-off-by: Paolo Abeni [ No conflicts, but move __mptcp_propagate_sndbuf() above the for-loop (mptcp_for_each_subflow()) present in this version, which will modify 'subflow' used by __mptcp_propagate_sndbuf() in this new patch. ] Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Sasha Levin --- net/mptcp/protocol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 09e1a93b7daab..c805d36fe50d5 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3428,7 +3428,6 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk, * uses the correct data */ mptcp_copy_inaddrs(nsk, ssk); - __mptcp_propagate_sndbuf(nsk, ssk); mptcp_rcv_space_init(msk, ssk); msk->rcvq_space.time = mptcp_stamp(); @@ -4027,6 +4026,8 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock, msk = mptcp_sk(newsk); msk->in_accept_queue = 0; + __mptcp_propagate_sndbuf(newsk, mptcp_subflow_tcp_sock(subflow)); + /* set ssk->sk_socket of accept()ed flows to mptcp socket. * This is needed so NOSPACE flag can be set from tcp stack. */ -- 2.53.0