Re: [ovs-dev] [PATCH net v2] openvswitch: meter: fix race when getting now_ms.

2021-05-13 Thread patchwork-bot+netdevbpf 
Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Thu, 13 May 2021 21:08:00 +0800 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [ovs-dev,net,v2] openvswitch: meter: fix race when getting now_ms.
https://git.kernel.org/netdev/net/c/e4df1b0c2435

You are awesome, thank you!
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Re: [ovs-dev] [PATCH net v2] openvswitch: meter: fix race when getting now_ms.

2021-05-13 Thread Ilya Maximets 
On 5/13/21 3:08 PM, Tao Liu wrote:
> 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-i.maxim...@ovn.org/
> 
> Fixes: 96fbc13d7e77 ("openvswitch: Add meter infrastructure")
> Signed-off-by: Tao Liu 
> Suggested-by: Ilya Maximets 
> ---
> Changelog:
> v2: just set negative long_delta_ms to zero in case of race for meter lock.
> v1: make now_ms protected by meter lock.
> ---

Thanks!
I didn't test it, but the change looks good to me.

Reviewed-by: Ilya Maximets 

>  net/openvswitch/meter.c | 8 
>  1 file changed, 8 insertions(+)
> 
> diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
> index 96b524c..896b8f5 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(>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.
> 

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[ovs-dev] [PATCH net v2] openvswitch: meter: fix race when getting now_ms.

2021-05-13 Thread Tao Liu 
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-i.maxim...@ovn.org/

Fixes: 96fbc13d7e77 ("openvswitch: Add meter infrastructure")
Signed-off-by: Tao Liu 
Suggested-by: Ilya Maximets 
---
Changelog:
v2: just set negative long_delta_ms to zero in case of race for meter lock.
v1: make now_ms protected by meter lock.
---
 net/openvswitch/meter.c | 8 
 1 file changed, 8 insertions(+)

diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
index 96b524c..896b8f5 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(>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.
-- 
1.8.3.1

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