Merge branch 'proc-per-ns'

Dmitry Torokhov says:

====================
Make /proc per net namespace objects belong to container

Currently [almost] all /proc objects belong to the global root, even if
data belongs to a given namespace within a container and (at least for
sysctls) we work around permssions checks to allow container's root to
access the data.

This series changes ownership of net namespace /proc objects
(/proc/net/self/* and /proc/sys/net/*) to be container's root and not
global root when there exists mapping for container's root in user
namespace.

This helps when running Android CTS in a container, but I think it makes
sense regardless.

Changes from V1:

- added fix for crash when !CONFIG_NET_NS (new patch #1)
- addressed Eric'c comments for error handling style in patch #3 and
  added his Ack
- adjusted patch #2 to use the same style of erro handling
- sent out as series instead of separate patches
====================

Signed-off-by: David S. Miller <davem@davemloft.net>