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| author | Liu Yu <allanyuliu@tencent.com> | 2014-04-30 17:34:09 +0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-04-30 16:12:22 -0400 |
| commit | 0cda345d1b2201dd15591b163e3c92bad5191745 (patch) | |
| tree | 9217f8842b799a02c7b2c531260c95b8029d9d27 /net/ipv4/tcp_cubic.c | |
| parent | e5744fe9d262d11131916d04ea79ea539fe296c0 (diff) | |
| download | lwn-0cda345d1b2201dd15591b163e3c92bad5191745.tar.gz lwn-0cda345d1b2201dd15591b163e3c92bad5191745.zip | |
tcp_cubic: fix the range of delayed_ack
commit b9f47a3aaeab (tcp_cubic: limit delayed_ack ratio to prevent
divide error) try to prevent divide error, but there is still a little
chance that delayed_ack can reach zero. In case the param cnt get
negative value, then ratio+cnt would overflow and may happen to be zero.
As a result, min(ratio, ACK_RATIO_LIMIT) will calculate to be zero.
In some old kernels, such as 2.6.32, there is a bug that would
pass negative param, which then ultimately leads to this divide error.
commit 5b35e1e6e9c (tcp: fix tcp_trim_head() to adjust segment count
with skb MSS) fixed the negative param issue. However,
it's safe that we fix the range of delayed_ack as well,
to make sure we do not hit a divide by zero.
CC: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Liu Yu <allanyuliu@tencent.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_cubic.c')
| -rw-r--r-- | net/ipv4/tcp_cubic.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c index 8bf224516ba2..b4f1b29b08bd 100644 --- a/net/ipv4/tcp_cubic.c +++ b/net/ipv4/tcp_cubic.c @@ -409,7 +409,7 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us) ratio -= ca->delayed_ack >> ACK_RATIO_SHIFT; ratio += cnt; - ca->delayed_ack = min(ratio, ACK_RATIO_LIMIT); + ca->delayed_ack = clamp(ratio, 1U, ACK_RATIO_LIMIT); } /* Some calls are for duplicates without timetamps */ |