linux-kernel - Re: [nsproxy] BUG: unable to handle kernel NULL pointer dereference at 0000000000000024

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Date:	Fri, 8 Mar 2013 17:38:52 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [nsproxy] BUG: unable to handle kernel NULL pointer dereference
 at 0000000000000024

On 3/7/13, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> Fengguang Wu <fengguang.wu@...el.com> writes:
>
>> Greetings,
>>
>> I got the below oops and the first bad commit is
>
> Doh!  On a second look that change is totally wrong.  Of course we need
> to up the ref-count every time we create a new process.  Especially if
> we don't do anything with namespaces.
>
> I was looking at it from the wrong angle last night.  I should have
> known better.
>
> Patch dropped.
>

Sad to know :( . From the debug messages, it's kmemcheck report. I
can't related the problem specified with the patch I've proposed.

It seems at task exit path, at switch_task_namespaces() - after my
patch atomic_dec_and_test(&ns->count) becomes true (-1), thus
free_nsproxy() gets called. But, free_nsproxy() shouldn't get called
here.

Am I right? Or there's something else?

Thanks,
Rakib
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