linux-kernel - Re: [PATCH v4 1/3] tracing: eprobe: remove duplicate is_good

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Date:   Tue, 21 Jun 2022 08:56:55 +0800
From:   Linyu Yuan <quic_linyyuan@...cinc.com>
To:     Tom Zanussi <zanussi@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...hat.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/3] tracing: eprobe: remove duplicate is_good_name()
 operation

hi Tom,

On 6/21/2022 2:38 AM, Tom Zanussi wrote:
> Hi Linyu,
>
> On Tue, 2022-06-14 at 08:48 +0800, Linyu Yuan wrote:
>> hi Tom,
>>
>> On 6/14/2022 5:01 AM, Tom Zanussi wrote:
>>> Hi Linhu,
>>>
>>> On Thu, 2022-06-02 at 20:10 +0800, Linyu Yuan wrote:
>>>> traceprobe_parse_event_name() already validate group and event
>>>> name,
>>>> there is no need to call is_good_name() after it.
>>>>
>>>> Signed-off-by: Linyu Yuan <quic_linyyuan@...cinc.com>
>>>> ---
>>>> v2: drop v1 change as it is NACK.
>>>>       add it to remove duplicate is_good_name().
>>>> v3: move it as first patch.
>>>> v4: no change
>>>>
>>>>    kernel/trace/trace_eprobe.c | 4 ----
>>>>    1 file changed, 4 deletions(-)
>>>>
>>>> diff --git a/kernel/trace/trace_eprobe.c
>>>> b/kernel/trace/trace_eprobe.c
>>>> index 7d44785..17d64e3 100644
>>>> --- a/kernel/trace/trace_eprobe.c
>>>> +++ b/kernel/trace/trace_eprobe.c
>>>> @@ -878,16 +878,12 @@ static int __trace_eprobe_create(int argc,
>>>> const char *argv[])
>>>>                   sanitize_event_name(buf1);
>>>>                   event = buf1;
>>>>           }
>>>> -       if (!is_good_name(event) || !is_good_name(group))
>>>> -               goto parse_error;
>>> traceprobe_parse_event_name() is only called if (event).  In the
>>> !event case, wouldn't the is_good_name() checks still be needed
>>> (since
>>> in that case buf1 is assigned to event)?
>> when user input no  event name, it will generate event name from
>> second
>> SYSTEM.EVENT,
>>
>> and it will validate with following traceprobe_parse_event_name().
>>
>>
> Right, but that happens in your second patch '[PATCH v5 2/3] tracing:
> auto generate event name when create a group of events', not this one.
>   
> So if you apply only this patch, the !event case will assign event but
> it will remain unchecked when used later in this function.
>
> It would make more sense to remove this check in patch 2/3 along with
> the code that does the generating...
thanks, will do like this.
>
>> (
>>
>> if you agree, i will send a new version to update a minor issue in
>> second patch,
>>
>>
>>           sys_event = argv[1];
>> -       ret = traceprobe_parse_event_name(&sys_event, &sys_name,
>> buf2,
>> -                                         sys_event - argv[1]);
>> -       if (ret || !sys_name)
>> +       ret = traceprobe_parse_event_name(&sys_event, &sys_name,
>> buf2, 0);
>> +       if (!sys_event || !sys_name)
>>                   goto parse_error;
>>
>> )
>>
>>>>    
>>>>           sys_event = argv[1];
>>>>           ret = traceprobe_parse_event_name(&sys_event, &sys_name,
>>>> buf2,
>>>>                                             sys_event - argv[1]);
>>>>           if (ret || !sys_name)
>>>>                   goto parse_error;
>>>> -       if (!is_good_name(sys_event) || !is_good_name(sys_name))
>>>> -               goto parse_error;
>>> I agree this one isn't needed.
> But keep this one in this patch, since it's useful on its own as a
> standalone cleanup regardless of whether or not patch 2/3 gets merged.
>
> Tom
>
>>> Thanks,
>>>
>>> Tom
>>>
>>>>    
>>>>           mutex_lock(&event_mutex);
>>>>           event_call = find_and_get_event(sys_name, sys_event);