From e3c4988d457bc5f89d2f0d07f294d45a95ecdce5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 1 May 2017 15:29:48 -0700 Subject: [PATCH] tcp: fix wraparound issue in tcp_lp 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 Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- 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 72f7218b03f5..8d24d0b03ea1 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, u32 num_acked, s32 rtt_us) { 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))