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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>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Christoph Hellwig <hch@infradead.org>, ast@kernel.org,
        axboe@kernel.dk, bfields@fieldses.org,
        bridge@lists.linux-foundation.org, chainsaw@gentoo.org,
        christian.brauner@ubuntu.com, chuck.lever@oracle.com,
        davem@davemloft.net, dhowells@redhat.com,
        gregkh@linuxfoundation.org, jarkko.sakkinen@linux.intel.com,
        jmorris@namei.org, josh@joshtriplett.org, keescook@chromium.org,
        keyrings@vger.kernel.org, kuba@kernel.org,
        lars.ellenberg@linbit.com, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-security-module@vger.kernel.org, nikolay@cumulusnetworks.com,
        philipp.reisner@linbit.com, ravenexp@gmail.com,
        roopa@cumulusnetworks.com, serge@hallyn.com, slyfox@gentoo.org,
        viro@zeniv.linux.org.uk, yangtiezhu@loongson.cn,
        netdev@vger.kernel.org, markward@linux.ibm.com,
        linux-s390 <linux-s390@vger.kernel.org>
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From:   Christian Borntraeger <borntraeger@de.ibm.com>
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Message-ID: <1bc537d4-59f7-b521-943f-307cec80e411@de.ibm.com>
Date:   Wed, 1 Jul 2020 17:26:26 +0200
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On 01.07.20 15:53, Luis Chamberlain wrote:
> On Wed, Jul 01, 2020 at 10:24:29PM +0900, Tetsuo Handa wrote:
>> 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).
> 
> br_stp_start() doesn't check for the raw value, it just checks for err
> or !err. So the patch, "umh: fix processed error when UMH_WAIT_PROC is
> used" propagates the correct error now.
> 
> Christian, can you try removing the binary temporarily and seeing if
> you get your bridge working?

As I matter of fact I do NOT have /sbin/bridge-stp installed.