From: Tao Liu thomas.liu@ucloud.cn
[ Upstream commit e4df1b0c24350a0f00229ff895a91f1072bd850d ]
We have observed meters working unexpected if traffic is 3+Gbit/s with multiple connections.
now_ms is not pretected by meter->lock, we may get a negative long_delta_ms when another cpu updated meter->used, then: delta_ms = (u32)long_delta_ms; which will be a large value.
band->bucket += delta_ms * band->rate; then we get a wrong band->bucket.
OpenVswitch userspace datapath has fixed the same issue[1] some time ago, and we port the implementation to kernel datapath.
[1] https://patchwork.ozlabs.org/project/openvswitch/patch/20191025114436.9746-1...
Fixes: 96fbc13d7e77 ("openvswitch: Add meter infrastructure") Signed-off-by: Tao Liu thomas.liu@ucloud.cn Suggested-by: Ilya Maximets i.maximets@ovn.org Reviewed-by: Ilya Maximets i.maximets@ovn.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/openvswitch/meter.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c index 8fbefd52af7f..e594b4d6b58a 100644 --- a/net/openvswitch/meter.c +++ b/net/openvswitch/meter.c @@ -611,6 +611,14 @@ bool ovs_meter_execute(struct datapath *dp, struct sk_buff *skb, spin_lock(&meter->lock);
long_delta_ms = (now_ms - meter->used); /* ms */ + if (long_delta_ms < 0) { + /* This condition means that we have several threads fighting + * for a meter lock, and the one who received the packets a + * bit later wins. Assuming that all racing threads received + * packets at the same time to avoid overflow. + */ + long_delta_ms = 0; + }
/* Make sure delta_ms will not be too large, so that bucket will not * wrap around below.