sysctl: allow to change limits for posix messages queues

sysctl: allow to change limits for posix messages queues

All parameters of posix messages queues (queues_max/msg_max/msgsize_max)
end up being limited by RLIMIT_MSGQUEUE.  The code in mqueue_get_inode is
where that limiting happens.

The RLIMIT_MSGQUEUE is bound to the user namespace and is counted
hierarchically.

We can allow root in the user namespace to modify the posix messages
queues parameters.

Link: https://lkml.kernel.org/r/6ad67f23d1459a4f4339f74aa73bac0ecf3995e1.1705333426.git.legion@kernel.org
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Link: https://lkml.kernel.org/r/7eb21211c8622e91d226e63416b1b93c079f60ee.1663756794.git.legion@kernel.org
Cc: Christian Brauner <brauner@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Joel Granados <joel.granados@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>