Re: [PATCH] Smack: replace capable() with ns_capable()

[Serge E. Hallyn]

On Tue, Jul 28, 2015 at 07:36:30AM -0700, Casey Schaufler wrote:
> On 7/26/2015 6:27 PM, Sungbae Yoo wrote:
> > So, Do you agree to allow the process to change its own labels?
> 
> No. This requires CAP_MAC_ADMIN. Smack is mandatory access control.
> Being in a namespace (as they are implemented today) is not sufficient.

"requires CAP_MAC_ADMIN" should probably read "requires
CAP_MAC_ADMIN against initial user namespace."  Any unprivileged
user can unshare a user_ns and get CAP_MAC_ADMIN.

I'm terribly sorry I'm not yet caught up on the smack-lsm thread.
But intuitively I'd think that you'd want a way for smack policy
to say "this label is allowed to create a user-ns which will be
allowed to CAP_MAC_ADMIN", so then smack_capable() can use that
information to cleanly deny CAP_MAC_ADMIN in namespaces.

-serge
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