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    Subject[PATCH 3.2 50/59] tcp: fix wraparound issue in tcp_lp
    3.2.92-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@google.com>

    commit a9f11f963a546fea9144f6a6d1a307e814a387e7 upstream.

    Be careful when comparing tcp_time_stamp to some u32 quantity,
    otherwise result can be surprising.

    Fixes: 7c106d7e782b ("[TCP]: TCP Low Priority congestion control")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [bwh: Backported to 3.2: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/ipv4/tcp_lp.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/net/ipv4/tcp_lp.c
    +++ b/net/ipv4/tcp_lp.c
    @@ -264,13 +264,15 @@ static void tcp_lp_pkts_acked(struct soc
    {
    struct tcp_sock *tp = tcp_sk(sk);
    struct lp *lp = inet_csk_ca(sk);
    + u32 delta;

    if (rtt_us > 0)
    tcp_lp_rtt_sample(sk, rtt_us);

    /* calc inference */
    - if (tcp_time_stamp > tp->rx_opt.rcv_tsecr)
    - lp->inference = 3 * (tcp_time_stamp - tp->rx_opt.rcv_tsecr);
    + delta = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
    + if ((s32)delta > 0)
    + lp->inference = 3 * delta;

    /* test if within inference */
    if (lp->last_drop && (tcp_time_stamp - lp->last_drop < lp->inference))
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