Comment # 3 on bug 965356 from Takashi Iwai

It seems that more backports are needed:

f0d62aec931e4ae3333c797d346dc4f188f454ba
  userns: Rename id_map_mutex to userns_state_mutex

9cc46516ddf497ea16e8d7cb986ae03a0f6b92f8
  userns: Add a knob to disable setgroups on a per user namespace basis

66d2f338ee4c449396b6f99f5e75cd18eb6df272
  userns: Allow setting gid_maps without privilege when setgroups is disabled

The second patch breaks kABI, so a fixup is needed as well.

I prepared a test kernel in OBS home:tiwai:bnc965308 repo.  The packages are
being built now.  Please check the package later, and let me know whether it
works for you.