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

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Date:   Wed, 1 Jul 2020 17:26:26 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Christoph Hellwig <hch@...radead.org>, ast@...nel.org,
        axboe@...nel.dk, bfields@...ldses.org,
        bridge@...ts.linux-foundation.org, chainsaw@...too.org,
        christian.brauner@...ntu.com, chuck.lever@...cle.com,
        davem@...emloft.net, dhowells@...hat.com,
        gregkh@...uxfoundation.org, jarkko.sakkinen@...ux.intel.com,
        jmorris@...ei.org, josh@...htriplett.org, keescook@...omium.org,
        keyrings@...r.kernel.org, kuba@...nel.org,
        lars.ellenberg@...bit.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-security-module@...r.kernel.org, nikolay@...ulusnetworks.com,
        philipp.reisner@...bit.com, ravenexp@...il.com,
        roopa@...ulusnetworks.com, serge@...lyn.com, slyfox@...too.org,
        viro@...iv.linux.org.uk, yangtiezhu@...ngson.cn,
        netdev@...r.kernel.org, markward@...ux.ibm.com,
        linux-s390 <linux-s390@...r.kernel.org>
Subject: Re: linux-next: umh: fix processed error when UMH_WAIT_PROC is used
 seems to break linux bridge on s390x (bisected)



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.