linux-kernel - Re: [PATCH 00/12] Add kdbus implementation

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Date:	Thu, 30 Oct 2014 13:24:34 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Karol Lewandowski <k.lewandowsk@...sung.com>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Linux API <linux-api@...r.kernel.org>,
	linux-kernel@...r.kernel.org, John Stultz <john.stultz@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
	Ryan Lortie <desrt@...rt.ca>,
	Simon McVittie <simon.mcvittie@...labora.co.uk>,
	daniel@...que.org, David Herrmann <dh.herrmann@...il.com>,
	Paul Moore <pmoore@...hat.com>,
	"casey.schaufler@...el.com" <casey.schaufler@...el.com>,
	marcel@...tmann.org, tixxdz@...ndz.org,
	javier.martinez@...labora.co.uk, alban.crequy@...labora.co.uk
Subject: Re: [PATCH 00/12] Add kdbus implementation

On Thu, Oct 30, 2014 at 08:55:56PM +0100, Karol Lewandowski wrote:
> On 2014-10-30 15:47, Greg Kroah-Hartman wrote:
> > On Thu, Oct 30, 2014 at 11:44:39AM +0100, Karol Lewandowski wrote:
> >> [ Sorry for breaking thread and resend - gmane rejected my original message
> >>   due to too long list of recipients... ]
> >>
> >> On 2014-10-30 00:40, Greg Kroah-Hartman wrote:
> >>
> >>> There is a 1815 line documentation file in this series, so we aren't
> >>> trying to not provide this type of information here at all.  But yes,
> >>> more background, about why this can't be done in userspace (zero copy,
> >>> less context switches, proper credential passing, timestamping, availble
> >>> at early-boot, LSM hooks for security models to tie into
> >>
> >> While you're at it... I did some work on proof-of-concept LSM patches for
> >> kdbus some time ago, see [1][2].  Currently, these are completely of date.
> >>
> >>  [1] https://github.com/lmctl/linux/commits/kdbus-lsm-v4.for-systemd-v212
> >>  [2] https://github.com/lmctl/kdbus/commit/aa0885489d19be92fa41c6f0a71df28763228a40
> >>
> >> May I ask if you guys have your own plan for LSM or maybe it would be
> >> worth to resurrect [1]?
> > 
> > The core calls are already mediated by LSM today, right?  We don't want
> > anyone to be parsing the data stream through an LSM, that idea got
> > rejected a long time ago as something that is really not a good idea.
> 
> Parsing data is out of question, of course, but this is not what we were
> proposing.

Glad to hear it :)

> > Other than that, I don't know exactly what your patches do, or why they
> > are needed, care to go into details?
> 
> Patches in question were supposed to add few hooks for kdbus-specific
> operations that doesn't seem to have compatible semantics with hooks
> currently available in LSM.
> 
> kdbus' bus introduces quite a few new concepts that we wanted to be able
> to limit based on MAC label/context, eg.
> 
>  - check flags at HELO stage (say disallow fd passing),
> 
>  - restrict ability to acquire name to certain subjects (for system bus),
> 
>  - disallow creation of new buses,
> 
>  - limit scope of broadcasts,
> 
>  - etc.

Nice list.

> Please take a look at hook list - I think most of names are self-explanatory:
> 
>   https://github.com/lmctl/linux/blob/a9fe4c33b6e5ab25a243e0590df406aabb6add12/include/linux/security.h#L1874
> 
> kdbus modifications were pretty light - with most visible change being
> addition of opaque security pointer to kdbus_bus and similar structs.

That looks very reasonable, care to make it up into a patch I can add to
the end of this series so it's easy to review and possibly submit as
part of it?

thanks,

greg k-h
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