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

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Message-ID: <20130820143722.GA12953@redhat.com>
Date:	Tue, 20 Aug 2013 16:37:22 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Serge Hallyn <serge.hallyn@...ntu.com>
Cc:	Chen Gang <gang.chen@...anux.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, 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.

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