ceph: add owner/capability checks for CEPH_IOC_SET_LAYOUT*

ceph: add owner/capability checks for CEPH_IOC_SET_LAYOUT*

These permission checks were already missing in the initial
impementation of these ioctls.  This Ceph allows any user who owns a
file descriptor to manipulate the layout of any file, even if they
don't have write permissions.

It might be a good idea to guard other ioctls with permission checks
as well or even disallow regular users (even if they own the file) to
manipulate layout settings completely, as this may be abused to DoS
the Ceph servers, but right now, I find it most urgent to have setter
checks at all.

Cc: stable@vger.kernel.org
Fixes: 8f4e91dee2a2 ("ceph: ioctls")
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Xiubo Li <xiubo.li@clyso.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>