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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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