tcp: reset sk_rx_dst in tcp_disconnect()

We have to reset the sk->sk_rx_dst when we disconnect a TCP
connection, because otherwise when we re-connect it this
dst reference is simply overridden in tcp_finish_connect().

This fixes a dst leak which leads to a loopback dev refcnt
leak. It is a long-standing bug, Kevin reported a very similar
(if not same) bug before. Thanks to Andrei for providing such
a reliable reproducer which greatly narrows down the problem.

Fixes: 41063e9dd119 ("ipv4: Early TCP socket demux.")
Reported-by: Andrei Vagin <avagin@gmail.com>
Reported-by: Kevin Xu <kaiwen.xu@hulu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b5ea036ca78144b86622cb0944d0b840f7225ec5..40aca7803cf2db25361dc7ef5c83ee6ea955c335 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2330,6 +2330,8 @@ int tcp_disconnect(struct sock *sk, int flags)
        tcp_init_send_head(sk);
        memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
        __sk_dst_reset(sk);
+       dst_release(sk->sk_rx_dst);
+       sk->sk_rx_dst = NULL;
        tcp_saved_syn_free(tp);
 
        /* Clean up fastopen related fields */