linux-kernel - Re: [rfc] fcntl: Add F_GETOWNER

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Message-ID: <20120328075549.GA2204@moon>
Date:	Wed, 28 Mar 2012 11:55:49 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...onical.com>
Subject: Re: [rfc] fcntl: Add F_GETOWNER_UIDS option

On Wed, Mar 28, 2012 at 12:51:02AM -0700, Eric W. Biederman wrote:
> > And we could require for a while that F_GETOWNER_UIDS should be called
> > from initial user namespace only. Then we could extend it for being
> > called from any user-namespace if such need appear. Or I miss
> > something?
> 
> Yes.  All that is needed in the short term to do this is a Kconfig
> dependency that limits it a kernel with user namespace support not
> built in something like: "depends !USER_NS"
> 
> Or a check like:
> 	if (current_user_ns() != init_user_ns)
>         	return -EINVAL;
> 
> Basically the mapping would ultimately become:
> uid = from_kuid(current_user_ns(), fown->uid);
> euid = from_kuid(current_user_ns(), fown->euid);
> 
> The different types allow a compile error if you forget the translation.

OK, thanks for the hint!

	Cyrill
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