On Fri, May 12, 2017 at 09:43:40AM +0200, Arnd Bergmann wrote:

How realistic and how useful would it be to first completely eliminate
the ones that are in loadable modules and then wrapping the definition
in #ifndef MODULE (or even make it an extern function)?

Should be fairly doable and might be a nice step towards cleaning the
mess up.  In fact with my seres a large part of those are gone, and
most of the remaining handler are ioctl handlers or what seems like
opencoded versions of probe_kernel_read.

But it won't help against exploits modifying addr_limit manually.