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 4927B315785; Mon, 4 May 2026 14:16:20 +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=1777904180; cv=none; b=MVhSPirbNMcaELVB3teXoNpoaafk1GP+Qz58k1d5C5Gthd1ae5inQaqJ5kjQcupf8nA3AonNaj3A/i7on2mrrsc3vhrfZevh3PTE72D4RNrMQPzfxj61z2zis+BWt5IGDLlwLd/TyXeJG0O1VKnK+4nuNPKZdz9/0qveCp7TPCI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777904180; c=relaxed/simple; bh=KmisXqjCh+1afvwi/hs8eXMiRTlm1+0CkB/jGX/mEr4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e3fKAz9/qyo4NyRA+rqOwV5F18A5QNqUVXkiMnD5UF9Wqf/459oN360YDzs4PywQAAYoWuI1tTqDSijpebX+WVVKL344upZLnGjXM0MU7UQN2F+H8iBNuIvHi0uG0Pf/AoV2cPKzt9guOGPHSQKnkgaOz+W0z8xOqnYvRuh+Kho= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=a2OlwnjD; 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="a2OlwnjD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D406BC2BCB8; Mon, 4 May 2026 14:16:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777904180; bh=KmisXqjCh+1afvwi/hs8eXMiRTlm1+0CkB/jGX/mEr4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a2OlwnjDKiCoheFnPowY6s6/iGjtxfcxn93v6IwDJs5hafbT37kfRFVhtMOOWRe2M 9kgRMlZmOLJOHlO0jOSIVFqyPvogBHOwfn7sN0JMLgZS7KLf1g9RD97v3FS4FjUkEd 7qaEUk0XeJ7GkJTgWbzHWNXXey8kS3iw7yw2r3cw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gang Yan , Paolo Abeni , "Matthieu Baerts (NGI0)" Subject: [PATCH 6.18 214/275] mptcp: sync the msk->sndbuf at accept() time Date: Mon, 4 May 2026 15:52:34 +0200 Message-ID: <20260504135151.022829547@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260504135142.929052779@linuxfoundation.org> References: <20260504135142.929052779@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 Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3428,7 +3428,6 @@ struct sock *mptcp_sk_clone_init(const s * 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(); @@ -4038,6 +4037,7 @@ static int mptcp_stream_accept(struct so } mptcp_rps_record_subflows(msk); + __mptcp_propagate_sndbuf(newsk, mptcp_subflow_tcp_sock(subflow)); /* Do late cleanup for the first subflow as necessary. Also * deal with bad peers not doing a complete shutdown.