tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0

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>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1e4c76d2b8278ba71d6cc2cf7ebfe483e241f76e..842b575f8fdddc41a41aa6f03fb9086cec7ee451 100644 (file)
--- 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);