From: Wei Wang <weiwan@google.com>
Date: Thu, 18 May 2017 18:22:33 +0000 (-0700)
Subject: tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0
X-Git-Tag: C0P2-H0.0--20200415~7543
X-Git-Url: https://git.somdevices.com/?a=commitdiff_plain;h=a10c510179b369f7d1e8cf77f43ee2db900c1ac9;p=linux.git

tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0


[ Upstream commit 499350a5a6e7512d9ed369ed63a4244b6536f4f8 ]

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  <andreyknvl@google.com>
Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1a4db27f5833..6b3d27e50317 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2297,6 +2297,10 @@ 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);