[PATCH] TCP: zero out rx_opt in tcp_disconnect()

When the server drops its connection, NFS client reconnects using the
same socket after disconnecting. If the new connection's SYN,ACK
doesn't contain the TCP timestamp option and the old connection's did,
tp->tcp_header_len is recomputed assuming no timestamp header but
tp->rx_opt.tstamp_ok remains set. Then tcp_build_and_update_options()
adds in a timestamp option past the end of the allocated TCP header,
overwriting TCP data, or when the data is in skb_shinfo(skb)->frags[],
overwriting skb_shinfo(skb) causing a crash soon after. (The issue was
debugged from such a crash.)

Similarly, wscale_ok and sack_ok also get set based on the SYN,ACK
packet but not reset on disconnect, since they are zeroed out at
initialization. The patch zeroes out the entire tp->rx_opt struct in
tcp_disconnect() to avoid this sort of problem.

Signed-off-by: Srinivas Aji <Aji_Srinivas@emc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 3834b10b51152aa24d3b69e08392d23274bca5f8..824c6b9c6af9d49854e1edcc0b7e44fc9be88f22 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1759,8 +1759,7 @@ int tcp_disconnect(struct sock *sk, int flags)
        tcp_clear_retrans(tp);
        inet_csk_delack_init(sk);
        sk->sk_send_head = NULL;
-       tp->rx_opt.saw_tstamp = 0;
-       tcp_sack_reset(&tp->rx_opt);
+       memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
        __sk_dst_reset(sk);
 
        BUG_TRAP(!inet->num || icsk->icsk_bind_hash);