Re: [PATCH v2 02/10] userns: Add per user namespace sysctls.

David Miller [off-list ref] writes:

From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)
Date: Mon, 25 Jul 2016 19:44:50 -0500

quoted

User namespaces have enabled unprivileged users access to a lot more
data structures and so to catch programs that go crazy we need a lot
more limits.  I believe some of those limits make sense per namespace.
As it is easy in some cases to say any more than Y number of those
per namespace is excessive.   For example a limit of 1,000,000 ipv4
routes per network namespaces is a sanity check as there are
currently 621,649 ipv4 prefixes advertized in bgp.

When we give a new namespace to unprivileged users, we honestly should
make the sysctl settings we give to them become "limits".  They can
further constrain the sysctl settings but may not raise them.

I won't disagree.  I was thinking in terms of global setting that
hold the limits for per namespace counters.  As we are talking sanity
check limits.

Perhaps we could get sophisticated and do something more but the simpler
we can make things and get the job done the better.

Eric