releases/4.9.28/tcp-fix-wraparound-issue-in-tcp_lp.patch

   1 From foo@baz Thu May 11 11:08:24 CEST 2017
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Mon, 1 May 2017 15:29:48 -0700
   4 Subject: tcp: fix wraparound issue in tcp_lp
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8
   9 [ Upstream commit a9f11f963a546fea9144f6a6d1a307e814a387e7 ]
  10
  11 Be careful when comparing tcp_time_stamp to some u32 quantity,
  12 otherwise result can be surprising.
  13
  14 Fixes: 7c106d7e782b ("[TCP]: TCP Low Priority congestion control")
  15 Signed-off-by: Eric Dumazet <edumazet@google.com>
  16 Signed-off-by: David S. Miller <davem@davemloft.net>
  17 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  18 ---
  19  net/ipv4/tcp_lp.c |    6 ++++--
  20  1 file changed, 4 insertions(+), 2 deletions(-)
  21
  22 --- a/net/ipv4/tcp_lp.c
  23 +++ b/net/ipv4/tcp_lp.c
  24 @@ -264,13 +264,15 @@ static void tcp_lp_pkts_acked(struct soc
  25  {
  26         struct tcp_sock *tp = tcp_sk(sk);
  27         struct lp *lp = inet_csk_ca(sk);
  28 +       u32 delta;
  29
  30         if (sample->rtt_us > 0)
  31                 tcp_lp_rtt_sample(sk, sample->rtt_us);
  32
  33         /* calc inference */
  34 -       if (tcp_time_stamp > tp->rx_opt.rcv_tsecr)
  35 -               lp->inference = 3 * (tcp_time_stamp - tp->rx_opt.rcv_tsecr);
  36 +       delta = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
  37 +       if ((s32)delta > 0)
  38 +               lp->inference = 3 * delta;
  39
  40         /* test if within inference */
  41         if (lp->last_drop && (tcp_time_stamp - lp->last_drop < lp->inference))