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

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Message-ID: <CAGXu5jKjjvVUKeRM0_RQx7T-r74-v9PofPYUoGJYg1xmWcc2dQ@mail.gmail.com>
Date:	Fri, 30 Mar 2012 12:46:51 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: [rfc] fcntl: Add F_GETOWNER_UIDS option

On Fri, Mar 30, 2012 at 9:15 AM, Serge E. Hallyn <serge@...lyn.com> wrote:
> Quoting Cyrill Gorcunov (gorcunov@...nvz.org):
>> On Fri, Mar 30, 2012 at 09:12:19AM -0500, Serge Hallyn wrote:
>> ...
>> > >
>> > > Yes, I wanna take a look on Eric's set first just to get right
>> > > "picture" of everything. And I wanted to find a minimal solution
>> > > with current kernel code base which could be extended in future.
>> > >
>> > > That said I guess the current init-ns-only approach should do the
>> > > trick for a while. And (thanks for pointing) I need to add a test
>> > > if a caller which tries to obtain uids has enought credentials
>> > > for that (probably CAP_FOWNER), right?
>> >
>> > Sorry, I'm not sure which caller you mean.  Neither f_setown nor
>> > f_getown require privilege right now.  Oh, you mean at restart?
>>
>> I meant the dumper. Yes, at moment f_get/setown requires no privileges
>> but I'm not sure if uid/euid is same or less sensible information
>> than pid, that's why I though CAP_FOWNER might be worth to add, no?
>
> Hmm, I would say no, but that might be a good question for kees.
>
> IMO it's not sensitive information and so no sense requiring privilege
> (and encouraging handing out of extra privilage to get at the info)

Nothing jumps out at me about just seeing uid/euid. Everything can be
construed as an information leak, but this don't seem like something
that needs special protection.

-Kees

-- 
Kees Cook
ChromeOS Security
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