ipc/sysctl: Allow to change ipc/mq sysctls inside ipc namespace

Right now ipc and mq limits count as per ipc namespace, but only real
root can change them.  The default values of these limits can only be
reduced.  Since only root can change the values, it is impossible to
reduce these limits in the rootless container.

We can allow limit changes within ipc namespace because mq parameters
are limited by RLIMIT_MSGQUEUE and ipc parameters are not limited to
anything other than cgroups.

Alexey Gladkov (3):
      sysctl: Allow change system v ipc sysctls inside ipc namespace
      docs: Add information about ipc sysctls limitations
      sysctl: Allow to change limits for posix messages queues

Eric W. Biederman (1):
      ipc/ipc_sysctl: Add missing include of linux/cred.h

 Documentation/admin-guide/sysctl/kernel.rst | 14 ++++++++---
 ipc/ipc_sysctl.c                            | 37 +++++++++++++++++++++++++++--
 ipc/mq_sysctl.c                             | 36 ++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+), 5 deletions(-)
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