linux-kernel - Re: [PATCH 5/9] user namespace: clamp down users of cap

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Date:	Thu, 20 Oct 2011 13:16:55 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	David Howells <dhowells@...hat.com>
Cc:	"Andrew G. Morgan" <morgan@...nel.org>,
	linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
	akpm@...ux-foundation.org, oleg@...hat.com, richard@....at,
	mikevs@...all.net, segoon@...nwall.com, gregkh@...e.de,
	eparis@...hat.com, "Serge E. Hallyn" <serge.hallyn@...onical.com>
Subject: Re: [PATCH 5/9] user namespace: clamp down users of cap_raised

Quoting David Howells (dhowells@...hat.com):
> 
> > #define NS_IS_NON_DEFAULT (current_user_ns() != &init_user_ns)
> 
> How about:
> 
> 	#define IN_ROOT_USER_NS (current_user_ns() == &init_user_ns)
> 
> And then:
> 
> 	if (!IN_ROOT_USER_NS() || !cap_raised(current_cap(), CAP_SYS_ADMIN)) {
> 
> I think it reads better.

My feeble brain does seem to process this faster.

I might make it !IN_INIT_USER_NS(), to be more consistent with
&init_user_ns.

Vasiliy had months ago suggested moving the whole idiom into its own
helper function.  Somehow I couldn't make the jump to this then...

thanks all,
-serge
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