From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang Subject: [PATCH net] tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0 Date: Thu, 18 May 2017 11:22:33 -0700 Message-ID: <20170518182233.100933-1-tracywwnj@gmail.com> Cc: Yuchung Cheng , Neal Cardwell , Eric Dumazet , Wei Wang To: David Miller , netdev@vger.kernel.org Return-path: Received: from mail-pf0-f178.google.com ([209.85.192.178]:33338 "EHLO mail-pf0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751704AbdERSWh (ORCPT ); Thu, 18 May 2017 14:22:37 -0400 Received: by mail-pf0-f178.google.com with SMTP id e193so27718270pfh.0 for ; Thu, 18 May 2017 11:22:37 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Wei Wang When tcp_disconnect() is called, inet_csk_delack_init() sets icsk->icsk_ack.rcv_mss to 0. This could potentially cause tcp_recvmsg() => tcp_cleanup_rbuf() => __tcp_select_window() call path to have division by 0 issue. So this patch initializes rcv_mss to TCP_MIN_MSS instead of 0. Reported-by: Andrey Konovalov Signed-off-by: Wei Wang Signed-off-by: Eric Dumazet Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng --- net/ipv4/tcp.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 1e4c76d2b827..842b575f8fdd 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2320,6 +2320,10 @@ int tcp_disconnect(struct sock *sk, int flags) tcp_set_ca_state(sk, TCP_CA_Open); tcp_clear_retrans(tp); inet_csk_delack_init(sk); + /* Initialize rcv_mss to TCP_MIN_MSS to avoid division by 0 + * issue in __tcp_select_window() + */ + icsk->icsk_ack.rcv_mss = TCP_MIN_MSS; tcp_init_send_head(sk); memset(&tp->rx_opt, 0, sizeof(tp->rx_opt)); __sk_dst_reset(sk); -- 2.13.0.303.g4ebf302169-goog