On Fri, Sep 21, 2018 at 08:03:48AM -0700, Yu-cheng Yu wrote:

Create a guard area between VMAs, to detect memory corruption.

Do I understand correctly that with this patch a user space program
no longer be able to place two mappings back to back? If it is so,
it will likely break a lot of things; for example, it's a common ring
buffer implementations technique, to map buffer memory twice back
to back in order to avoid special handling of items wrapping its end.