netdev - Re: [PATCH net-next v3 1/4] net/sched: act_pedit: use extack in 'ex' parsing errors

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Date:   Fri, 17 Mar 2023 17:29:55 -0300
From:   Pedro Tammela <pctammela@...atatu.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net-next v3 1/4] net/sched: act_pedit: use extack in 'ex'
 parsing errors

On 17/03/2023 17:24, Simon Horman wrote:
> Hi Pedro,
> 
> On Fri, Mar 17, 2023 at 04:51:32PM -0300, Pedro Tammela wrote:
>> We have extack available when parsing 'ex' keys, so pass it to
>> tcf_pedit_keys_ex_parse and add more detailed error messages.
> 
> This part looks good.
> 
>> While at it, remove redundant code from the 'err_out' label code path.
> 
> But I think it would be better to do one thing at a time.
> 
>>
>> Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>
>> Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
>> ---
>>   net/sched/act_pedit.c | 20 ++++++++++----------
>>   1 file changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
>> index 4559a1507ea5..cd3cbe397e87 100644
>> --- a/net/sched/act_pedit.c
>> +++ b/net/sched/act_pedit.c
>> @@ -35,7 +35,7 @@ static const struct nla_policy pedit_key_ex_policy[TCA_PEDIT_KEY_EX_MAX + 1] = {
>>   };
>>   
>>   static struct tcf_pedit_key_ex *tcf_pedit_keys_ex_parse(struct nlattr *nla,
>> -							u8 n)
>> +							u8 n, struct netlink_ext_ack *extack)
>>   {
>>   	struct tcf_pedit_key_ex *keys_ex;
>>   	struct tcf_pedit_key_ex *k;
>> @@ -56,25 +56,25 @@ static struct tcf_pedit_key_ex *tcf_pedit_keys_ex_parse(struct nlattr *nla,
>>   		struct nlattr *tb[TCA_PEDIT_KEY_EX_MAX + 1];
>>   
>>   		if (!n) {
>> -			err = -EINVAL;
>> +			NL_SET_ERR_MSG_MOD(extack, "Can't parse more extended keys than requested");
>>   			goto err_out;
>>   		}
>> +
>>   		n--;
>>   
>>   		if (nla_type(ka) != TCA_PEDIT_KEY_EX) {
>> -			err = -EINVAL;
>> +			NL_SET_ERR_MSG_MOD(extack, "Unknown attribute, expected extended key");
>>   			goto err_out;
>>   		}
> 
> perhaps I'm missing something terribly obvious but what I see is that
> this code sits in a loop and the initial value of err is -EINVAL.
> `
>>   
>> -		err = nla_parse_nested_deprecated(tb, TCA_PEDIT_KEY_EX_MAX,
>> -						  ka, pedit_key_ex_policy,
>> -						  NULL);
>> +		err = nla_parse_nested_deprecated(tb, TCA_PEDIT_KEY_EX_MAX, ka,
>> +						  pedit_key_ex_policy, extack);
>>   		if (err)
>>   			goto err_out;
> 
> If nla_parse_nested_deprecated() succeeds then, here, err == 0
> 
>>   
>>   		if (!tb[TCA_PEDIT_KEY_EX_HTYPE] ||
>>   		    !tb[TCA_PEDIT_KEY_EX_CMD]) {
>> -			err = -EINVAL;
>> +			NL_SET_ERR_MSG_MOD(extack, "Extended Pedit missing required attributes");
>>   			goto err_out;
> 
> If, f.e.,  this fails the code will now branch to err_out with err == 0.
> Which will return ERR_PTR(err);
> 

Correct, I sent this change too fast and should have been more thorough.
I will try to be more careful in the future.
Thanks again!