netdev - Re: [RFC PATCH v3 2/2] tun: fix LSM/SELinux labeling of tun/tap devices

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Date:	Thu, 20 Dec 2012 16:58:45 -0500
From:	Eric Paris <eparis@...isplace.org>
To:	Paul Moore <pmoore@...hat.com>
Cc:	Jason Wang <jasowang@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>,
	SE-Linux <selinux@...ho.nsa.gov>
Subject: Re: [RFC PATCH v3 2/2] tun: fix LSM/SELinux labeling of tun/tap devices

You may add my Ack to the series.

-Eric

On Wed, Dec 19, 2012 at 11:58 AM, Paul Moore <pmoore@...hat.com> wrote:
> On Wednesday, December 19, 2012 01:46:25 PM Jason Wang wrote:
>> On 12/19/2012 07:08 AM, Michael S. Tsirkin wrote:
>> > On Tue, Dec 18, 2012 at 05:53:52PM -0500, Paul Moore wrote:
>> >> This patch corrects some problems with LSM/SELinux that were introduced
>> >> with the multiqueue patchset.  The problem stems from the fact that the
>> >> multiqueue work changed the relationship between the tun device and its
>> >> associated socket; before the socket persisted for the life of the
>> >> device, however after the multiqueue changes the socket only persisted
>> >> for the life of the userspace connection (fd open).  For non-persistent
>> >> devices this is not an issue, but for persistent devices this can cause
>> >> the tun device to lose its SELinux label.
>> >>
>> >> We correct this problem by adding an opaque LSM security blob to the
>> >> tun device struct which allows us to have the LSM security state, e.g.
>> >> SELinux labeling information, persist for the lifetime of the tun
>> >> device.  In the process we tweak the LSM hooks to work with this new
>> >> approach to TUN device/socket labeling and introduce a new LSM hook,
>> >> security_tun_dev_attach_queue(), to approve requests to attach to a
>> >> TUN queue via TUNSETQUEUE.
>> >>
>> >> The SELinux code has been adjusted to match the new LSM hooks, the
>> >> other LSMs do not make use of the LSM TUN controls.  This patch makes
>> >> use of the recently added "tun_socket:attach_queue" permission to
>> >> restrict access to the TUNSETQUEUE operation.  On older SELinux
>> >> policies which do not define the "tun_socket:attach_queue" permission
>> >> the access control decision for TUNSETQUEUE will be handled according
>> >> to the SELinux policy's unknown permission setting.
>> >>
>> >> Signed-off-by: Paul Moore <pmoore@...hat.com>
>> >
>> > Looks good to me. A comment not directly related to this patch, below.
>>
>> Good to me too, will do some test on this.
>
> Great.  I'll do some more testing and make sure the LSM and SELinux crowd are
> okay with the changes.
>
> --
> paul moore
> security and virtualization @ redhat
>
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