Re: [PATCH v2] userfaultfd: allow registration of ranges below mmap_min_addr

[Denis M. Karpov]

Thanks, Liam. Andrew has already picked up the patch and added the stable tag.
I'll make sure to include it from the start next time.

On Thu, Apr 9, 2026 at 11:16 PM Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> wrote:
>
> * Denis M. Karpov <komlomal@xxxxxxxxx> [260409 11:54]:
> > On Thu, Apr 9, 2026 at 6:17 PM Mike Rapoport <rppt@xxxxxxxxxx> wrote:
> > > On Thu, Apr 09, 2026 at 01:30:07PM +0100, Pedro Falcato wrote:
> > > > This looks relatively safe. However, I'm not sure if we want this in stable.
> > > > This has been broken for 11 years now, with no complaints.
> > >
> > > I believe Denis has a new usecase that wasn't there for those 11 years :)
> > >
> > > Denis, can you share more details about your usecase for us to better
> > > understand importance of backporting this to stable?
> > Hello Mike.
> > Actually, there is nothing new about the use case. We simply started using
> > UFFD instead of the classic mprotect approach in the binary translator to
> > track application writes. During development, we encountered this bug.
> > The translator cannot control where the translated application chooses
> > to map its
> > memory and if the app requires a low-address area, UFFD fails, whereas
> > mprotect would work just fine. I believe this is a genuine logic bug rather than
> > an improvement, and I would appreciate including the fix in stable.
>
> Then you should have cc'ed stable (with the tag too).
>
> I'm fine with it backported or not.
>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
>