+ user-ns-implement-user-ns-unshare-remove-config_user_ns.patch added to -mm tree

[Eric W. Biederman]

"Serge E. Hallyn" <serue at us.ibm.com> writes:

> Allow me to re-ask a fundamental question:  do we want the uid namespace
> to stick to turning uid checks into (uid,ns) checks?  or do we want the
> uid namespaces to try to protect against root in other namespaces?

I am fairly certain we want to at least make the checks (uid, ns) checks.
That gives a minimal level of protection against root in other namespaces,
as the lesser root does not match the (uid, ns) check for the system root.

Exactly how capabilities play into this I'm not quite certain, but something
important to understand.  Especially for suid root executables.

> If we go with the first, we can always enforce protection against root
> in other namespaces using LSMs.  SELinux users have what they need, and
> others can use a trivial new LSM.

What is the hole you see with root in other namespaces that needs an
LSM, the only hole I know of currently is the incomplete state of the
(uid/gid, ns) checks.  

Not that I don't think an LSM couldn't improve the situation.
Although if I have to deal with the LSM insanity much more I'm going
to lobby for changing the concept it to an interapplication firewall,
and get all of the stupid code into the kernel.

Eric