Re: [kernel-hardening] Re: [PATCH resend 2/2] userns: control capabilities of some user namespaces

On Fri, Nov 10, 2017 at 1:46 PM, Serge E. Hallyn [off-list ref] wrote:

Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):

quoted

single sandbox.  I am not at all certain that the capabilities is the
proper place to limit code reachability.

Right, I keep having this gut feeling that there is another way we
should be doing that.  Maybe based on ksplice or perf, or maybe more
based on subsystems.  And I hope someone pursues that.  But I can't put
my finger on it, and meanwhile the capability checks obviously *are* in
fact gates...

Well, I don't mind if there is a better solution available. The
proposed solution is not adding too much or complex code and using a
bit and a sysctl and will be sitting dormant. When we have complete
solution, this addition should not be a burden to maintain because of
it's non-invasive footprint.

I will push the next version of the patch-set that implements Serge's finding.

Thanks,
--mahesh..

[PS: I'll be soon traveling again and moving to an area where
connectivity will be scarce / unreliable. So please expect lot more
delays in my responses.]

-serge