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authorLiu Yu <allanyuliu@tencent.com>2014-04-30 17:34:09 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-05-31 13:20:36 -0700
commitb2bb9ffdced59893208af375086e0cdb17a8d3c3 (patch)
treeb7b95bad524b6b533c14b42806b2b2120a9f87e2
parentcea2f34c5fa7f414f648fc7034ce76d5eb0d48ff (diff)
tcp_cubic: fix the range of delayed_ack
[ Upstream commit 0cda345d1b2201dd15591b163e3c92bad5191745 ] 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/ipv4/tcp_cubic.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 828e4c3ffbaf..121a9a22dc98 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 */