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    Subject[PATCH 3.2 098/106] tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0
    3.2.93-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Wei Wang <weiwan@google.com>

    commit 499350a5a6e7512d9ed369ed63a4244b6536f4f8 upstream.

    When tcp_disconnect() is called, inet_csk_delack_init() sets
    icsk->icsk_ack.rcv_mss to 0.
    This could potentially cause tcp_recvmsg() => tcp_cleanup_rbuf() =>
    __tcp_select_window() call path to have division by 0 issue.
    So this patch initializes rcv_mss to TCP_MIN_MSS instead of 0.

    Reported-by: Andrey Konovalov <andreyknvl@google.com>
    Signed-off-by: Wei Wang <weiwan@google.com>
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: Neal Cardwell <ncardwell@google.com>
    Signed-off-by: Yuchung Cheng <ycheng@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/ipv4/tcp.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -2106,6 +2106,10 @@ int tcp_disconnect(struct sock *sk, int
    tcp_set_ca_state(sk, TCP_CA_Open);
    tcp_clear_retrans(tp);
    inet_csk_delack_init(sk);
    + /* Initialize rcv_mss to TCP_MIN_MSS to avoid division by 0
    + * issue in __tcp_select_window()
    + */
    + icsk->icsk_ack.rcv_mss = TCP_MIN_MSS;
    tcp_init_send_head(sk);
    memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
    __sk_dst_reset(sk);
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