netdev - Re: [PATCH] net: mellanox: mlx5: fix error return code of mlx5e_stats

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Date:   Tue, 9 Mar 2021 11:44:46 +0200
From:   Roi Dayan <roid@...dia.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>, <saeedm@...dia.com>,
        <leon@...nel.org>, <davem@...emloft.net>, <kuba@...nel.org>
CC:     <netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: mellanox: mlx5: fix error return code of
 mlx5e_stats_flower()



On 2021-03-09 10:32 AM, Jia-Ju Bai wrote:
> 
> 
> On 2021/3/9 16:24, Roi Dayan wrote:
>>
>>
>> On 2021-03-09 10:20 AM, Roi Dayan wrote:
>>>
>>>
>>> On 2021-03-06 3:47 PM, Jia-Ju Bai wrote:
>>>> When mlx5e_tc_get_counter() returns NULL to counter or
>>>> mlx5_devcom_get_peer_data() returns NULL to peer_esw, no error return
>>>> code of mlx5e_stats_flower() is assigned.
>>>> To fix this bug, err is assigned with -EINVAL in these cases.
>>>>
>>>> Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
>>>> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
>>>> ---
>>>>   drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 12 +++++++++---
>>>>   1 file changed, 9 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c 
>>>> b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
>>>> index 0da69b98f38f..1f2c9da7bd35 100644
>>>> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
>>>> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
>>>> @@ -4380,8 +4380,10 @@ int mlx5e_stats_flower(struct net_device 
>>>> *dev, struct mlx5e_priv *priv,
>>>>       if (mlx5e_is_offloaded_flow(flow) || flow_flag_test(flow, CT)) {
>>>>           counter = mlx5e_tc_get_counter(flow);
>>>> -        if (!counter)
>>>> +        if (!counter) {
>>>> +            err = -EINVAL;
>>>>               goto errout;
>>>> +        }
>>>>           mlx5_fc_query_cached(counter, &bytes, &packets, &lastuse);
>>>>       }
>>>> @@ -4390,8 +4392,10 @@ int mlx5e_stats_flower(struct net_device 
>>>> *dev, struct mlx5e_priv *priv,
>>>>        * un-offloaded while the other rule is offloaded.
>>>>        */
>>>>       peer_esw = mlx5_devcom_get_peer_data(devcom, 
>>>> MLX5_DEVCOM_ESW_OFFLOADS);
>>>> -    if (!peer_esw)
>>>> +    if (!peer_esw) {
>>>> +        err = -EINVAL;
>>>
>>> note here it's not an error. it could be there is no peer esw
>>> so just continue with the stats update.
>>>
>>>>           goto out;
>>>> +    }
>>>>       if (flow_flag_test(flow, DUP) &&
>>>>           flow_flag_test(flow->peer_flow, OFFLOADED)) {
>>>> @@ -4400,8 +4404,10 @@ int mlx5e_stats_flower(struct net_device 
>>>> *dev, struct mlx5e_priv *priv,
>>>>           u64 lastuse2;
>>>>           counter = mlx5e_tc_get_counter(flow->peer_flow);
>>>> -        if (!counter)
>>>> +        if (!counter) {
>>>> +            err = -EINVAL;
>>
>> this change is problematic. the current goto is to do stats update with
>> the first counter stats we got but if you now want to return an error
>> then you probably should not do any update at all.
> 
> Thanks for your reply :)
> I am not sure whether an error code should be returned here?
> If so, flow_stats_update(...) should not be called here?
> 
> 
> Best wishes,
> Jia-Ju Bai
> 

basically flow and peer_flow should be valid and protected from changes,
and counter should be valid.
it looks like the check here is more of a sanity check if something goes
wrong but shouldn't. you can just let it be, update the stats from the
first queried counter.


>>
>>>>               goto no_peer_counter;
>>>> +        }
>>>>           mlx5_fc_query_cached(counter, &bytes2, &packets2, &lastuse2);
>>>>           bytes += bytes2;
>>>>
>>>
>>>
>