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

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Message-ID: <51356BD8.4040408@cn.fujitsu.com>
Date:	Tue, 05 Mar 2013 11:51:52 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	"Eric W. Biederman" <raphael.scarv@...il.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 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.

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