linux-kernel - Re: [PATCH] kernel: user_namespace: always set the return parameter 'new_cred' when call unshare

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Date:	Wed, 21 Aug 2013 12:15:28 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Serge Hallyn <serge.hallyn@...ntu.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Andy Lutomirski <luto@...capital.net>,
	"dhowells@...hat.com" <dhowells@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel: user_namespace: always set the return parameter
 'new_cred' when call unshare_userns() successfully.

On 08/20/2013 10:37 PM, Oleg Nesterov wrote:
> On 08/20, Serge Hallyn wrote:
>>
>> Quoting Chen Gang (gang.chen@...anux.com):
>>> When unshare_userns() succeed, recommend to always set the return
>>> parameter which may be used by caller.
>>>
>>> The caller has rights to call it with 'new_cred' uninitialized, if
>>> succeed, the caller can assume the 'new_cred' has been initialized.
>>
>> But the only existing caller (sys_unshare) does in fact initialize it to
>> NULL.  So while this patch does no harm, is it necessary?
> 
> Agreed.
> 
> Plus, with this patch unshare_userns() becomes "inconsistent" compared
> to other unshare_ helpers.
> 
> Oleg.
> 
> 
> 

Hmm... for static functions, they don't need, but for extern functions,
recommend to do so.


For "unshare_ helpers", I find 3 extern functions:

  unshare_files() which already set value.
  unshare_userns() and unshare_nsproxy_namespaces() which not set.

In my opinion, recommend to always set the return parameter when
succeed, for the 2 left extern functions.


Thanks.
-- 
Chen Gang
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