[PATCH net] tcp: fix wraparound issue in tcp_lp
From: Eric Dumazet <hidden>
Date: 2017-05-01 22:29:51
Subsystem:
networking [general], networking [tcp], tcp low priority module, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, "Wong Hoi Sing, Edison", "Hung Hing Lun, Mike", Linus Torvalds
From: Eric Dumazet <edumazet@google.com>
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>
---
net/ipv4/tcp_lp.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c
index 046fd3910873306d74207615d6997e1c847ea361..d6fb6c067af4641f232b94e7c590c212648e8173 100644
--- a/net/ipv4/tcp_lp.c
+++ b/net/ipv4/tcp_lp.c@@ -264,13 +264,15 @@ static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample) { struct tcp_sock *tp = tcp_sk(sk); struct lp *lp = inet_csk_ca(sk); + u32 delta; if (sample->rtt_us > 0) tcp_lp_rtt_sample(sk, sample->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))