linux-next: umh: fix processed error when UMH_WAIT_PROC is used seems to break linux bridge on s390x (bisected)

[Tetsuo Handa]

On 2020/07/01 19:08, Christian Borntraeger wrote:
> 
> 
> On 30.06.20 19:57, Luis Chamberlain wrote:
>> On Fri, Jun 26, 2020 at 02:54:10AM +0000, Luis Chamberlain wrote:
>>> On Wed, Jun 24, 2020 at 08:37:55PM +0200, Christian Borntraeger wrote:
>>>>
>>>>
>>>> On 24.06.20 20:32, Christian Borntraeger wrote:
>>>> [...]> 
>>>>> So the translations look correct. But your change is actually a sematic change
>>>>> if(ret) will only trigger if there is an error
>>>>> if (KWIFEXITED(ret)) will always trigger when the process ends. So we will always overwrite -ECHILD
>>>>> and we did not do it before. 
>>>>>
>>>>
>>>> So the right fix is
>>>>
>>>> diff --git a/kernel/umh.c b/kernel/umh.c
>>>> index f81e8698e36e..a3a3196e84d1 100644
>>>> --- a/kernel/umh.c
>>>> +++ b/kernel/umh.c
>>>> @@ -154,7 +154,7 @@ static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
>>>>                  * the real error code is already in sub_info->retval or
>>>>                  * sub_info->retval is 0 anyway, so don't mess with it then.
>>>>                  */
>>>> -               if (KWIFEXITED(ret))
>>>> +               if (KWEXITSTATUS(ret))
>>>>                         sub_info->retval = KWEXITSTATUS(ret);

Well, it is not br_stp_call_user() but br_stp_start() which is expecting
to set sub_info->retval for both KWIFEXITED() case and KWIFSIGNALED() case.
That is, sub_info->retval needs to carry raw value (i.e. without "umh: fix
processed error when UMH_WAIT_PROC is used" will be the correct behavior).