linux-kernel - Re: [PATCH 1/1] kernel/pid_namespace.c: Fixing a lack of cleanup (Probable resources leak).

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Date:	Tue, 5 Mar 2013 02:04:45 -0300
From:	Raphael S Carvalho <raphael.scarv@...il.com>
To:	Gao feng <gaofeng@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] kernel/pid_namespace.c: Fixing a lack of cleanup
 (Probable resources leak).

On Tue, Mar 5, 2013 at 12:51 AM, Gao feng <gaofeng@...fujitsu.com> wrote:
> On 2013/03/05 11:26, Eric W. Biederman wrote:
>> From: Raphael S.Carvalho <raphael.scarv@...il.com>
>>
>> Starting point: create_pid_namespace()
>>
>> Suppose create_pid_cachep() was executed sucessfully, thus:
>> pcache was allocated by kmalloc().
>> cachep received a cache created by kmem_cache_create().
>> and pcache->list was added to the list pid_caches_lh.
>>
>> So what would happen if proc_alloc_inum() returns an error?
>> The resources allocated by create_pid_namespace() would be deallocated!
>> How about those resources allocated by create_pid_cachep()?
>> By knowing that, I created this patch in order to fix that!
>>
>> Signed-off-by: Raphael S.Carvalho <raphael.scarv@...il.com>
>> ---
>
> Actually I noticed this problem and I think it is not a BUG.
> Since the pid_cache is created for all pid namespace which have the same level.
> Even this pid namespace is failed to create, the pid_cache will not be leaked, Other
> pid namespace which has the same level will use the pid_cache and no need to
> allocate it again. In other words, the pid_cache for every level pid namespace will
> only be created once.
>
> I also think this patch add a bug,because there may be other pid namespace's pid_cachep
> points to the same pid_cache which will be free at the by label out_free_cachep.
>

Yeah, I found the snippet of code which searches for the pcache with
the same level.
 46        list_for_each_entry(pcache, &pid_caches_lh, list)
 47                if (pcache->nr_ids == nr_ids)
 48                        goto out;

Regards,
Raphael S.Carvalho
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