linux-kernel - Re: [PATCH] namespace:unmount pid_namespace's proc_mnt when copy_net

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Message-ID: <50938C2D.90908@cn.fujitsu.com>
Date:	Fri, 02 Nov 2012 17:02:37 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	linux-kernel@...r.kernel.org, containers@...ts.linux-foundation.org
Subject: Re: [PATCH] namespace:unmount pid_namespace's proc_mnt when copy_net_ns
 failed

于 2012年11月02日 16:54, Eric W. Biederman 写道:
> Gao feng <gaofeng@...fujitsu.com> writes:
> 
>> 于 2012年11月02日 15:02, Eric W. Biederman 写道:
>>> Gao feng <gaofeng@...fujitsu.com> writes:
>>>
>>>> we should call pid_ns_release_proc to unmount pid_namespace's
>>>> proc_mnt when copy_net_ns failed in function create_new_namespaces.
>>>>
>>>> otherwise,the proc_mnt will not be freed and because the super_block
>>>> of proc_mnt also add the reference of the pid_namespace,so this
>>>> pid_namespace will never be released too.
>>>
>>> Ouch!
>>>
>>> Have you encountered this failure in practice or is this just from
>>> review?
>>
>> I add some printk in pid_ns_release_proc,it's not called in above case.
>> when copy_net_ns failed,this pid_namespace is not used by any task,
>> so proc_flush_task can't call pid_ns_release_proc to umount this pidns->proc_mnt.
>> it's the only chance we can unmount this pindns->proc_mnt.
>>
>> With this patch,everything runs well.
> 
> I have reviewed the code and I don't doubt that this is necessary.
> 
> What caused you to look into this failure?  Is there some semi-practical
> real world case that someone is hitting?
> 

So far,there is no case hitting this problem.
Thanks

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