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

Yu-cheng Yu
2018-10-03T16:06:53Z

On Tue, 2018-10-02 at 22:36 -0700, Andy Lutomirski wrote:
> 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

I did some mmap tests with/without MAP_FIXED, and it works as intended.
In addition to the ring buffer, are there other test cases?

Yu-cheng