[PATCH] tcp: fix tcp_disconnect() not clear tp->fastopen_rsk sometimes

[chunguo feng]

From: fengchunguo <chunguo.feng@xxxxxxxxxxx>

This patch avoids fastopen_rsk not be cleared every times, then occur 
the below BUG_ON:
tcp_v4_destroy_sock
	->BUG_ON(tp->fastopen_rsk);

When playback some videos from netwrok,used tcp_disconnect continually.
        Call trace:
        kfree+0x210/0x250
        tcp_v4_destroy_sock+0xb8/0x1b0
        tcp_v6_destroy_sock+0x20/0x34
        inet_csk_destroy_sock+0x58/0x114
        tcp_done+0x144/0x148
        tcp_rcv_state_process+0x5d4/0xe3c
        tcp_v4_do_rcv+0x74/0x240
        tcp_v4_rcv+0xaac/0xba0
        ip_local_deliver_finish+0xe8/0x25c
        ip_local_deliver+0x60/0x118
        ip_rcv+0x70/0x108
        __netif_receive_skb_core+0x6f8/0xb80
        process_backlog+0xe4/0x1f4
        napi_poll+0x94/0x1ec
        net_rx_action+0xe4/0x224
        __do_softirq+0x16c/0x3bc
        do_softirq.part.15+0x70/0x74
        do_softirq+0x24/0x2c
        netif_rx_ni+0x108/0x138
        dhd_rxf_thread+0x134/0x1e4
        kthread+0x114/0x140
        ret_from_fork+0x10/0x18

Signed-off-by: fengchunguo <chunguo.feng@xxxxxxxxxxx>
---
 net/ipv4/tcp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 61082065b26a..f5c354c0b24c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2655,6 +2655,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	/* Clean up fastopen related fields */
 	tcp_free_fastopen_req(tp);
 	inet->defer_connect = 0;
+	tp->fastopen_rsk = 0;
 
 	WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
 
-- 
2.22.0