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Subject: Re: linux-next: umh: fix processed error when UMH_WAIT_PROC is used
 seems to break linux bridge on s390x (bisected)
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     Christoph Hellwig <hch@infradead.org>, ast@kernel.org,
        axboe@kernel.dk, bfields@fieldses.org,
        bridge@lists.linux-foundation.org, chainsaw@gentoo.org,
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        linux-s390 <linux-s390@vger.kernel.org>
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From:   Christian Borntraeger <borntraeger@de.ibm.com>
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Message-ID: <feb6a8c4-2b94-3f95-6637-679e089a71ca@de.ibm.com>
Date:   Fri, 26 Jun 2020 07:22:34 +0200
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On 26.06.20 04:54, 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);
>>         }
>>  
>> I think.
> 
> Nope, the right form is to check for WIFEXITED() before using WEXITSTATUS().

But this IS a change over the previous code, no?
I will test next week as I am travelling right now.