Re: [RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs

Andy Lutomirski
2018-10-03T05:36:29Z

On Tue, Oct 2, 2018 at 9:55 PM Eugene Syromiatnikov <esyr@redhat.com> wrote:
>
> 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.

I haven't checked what the patch actually does, but it shouldn't have
any affect on MAP_FIXED or the new no-replace MAP_FIXED variant.

--Andy