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Subject[ 11/23] tcp: drop SYN+FIN messages
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.0-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <eric.dumazet@gmail.com>

commit fdf5af0daf8019cec2396cdef8fb042d80fe71fa upstream.

Denys Fedoryshchenko reported that SYN+FIN attacks were bringing his
linux machines to their limits.

Dont call conn_request() if the TCP flags includes SYN flag

Reported-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/ipv4/tcp_input.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5761,6 +5761,8 @@ int tcp_rcv_state_process(struct sock *s
goto discard;

if (th->syn) {
+ if (th->fin)
+ goto discard;
if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
return 1;




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