lkml.org 
[lkml]   [2022]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] mm/hugetlb: avoid corrupting page->mapping in hugetlb_mcopy_atomic_pte
On Fri, Jul 15, 2022 at 10:39 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Fri, Jul 15, 2022 at 10:28:44AM -0700, Axel Rasmussen wrote:
> > On Fri, Jul 15, 2022 at 10:07 AM Peter Xu <peterx@redhat.com> wrote:
> > >
> > > On Fri, Jul 15, 2022 at 09:45:37AM -0700, Axel Rasmussen wrote:
> > > > I agree we should either:
> > > > - Update the UFFD selftest to exercise this case
> > > > - Or, don't allow it, update vma_can_userfault() to also require VM_SHARED
> > > > for VM_UFFD_MINOR registration.
> > > >
> > > > The first one is unfortunately not completely straightforward as Peter
> > > > described. I would say it's probably not worth holding up this fix while we
> > > > wait for it to happen?
> > >
> > > Agreed, Andrew has already queued it. It actually is a real fix since we
> > > never forbid the user running private mappings upon minor faults, so
> > > it's literally a bug in kernel irrelevant of the kselftest.
> > >
> > > >
> > > > I don't really have a strong preference between the two. The second option
> > > > is what I originally proposed in the first version of the minor fault
> > > > series, so going back to that isn't a problem at least from my perspective.
> > > > If in the future we find a real use case for this, we could always easily
> > > > re-enable it and add selftests for it at that point.
> > >
> > > I'd go for fixing the test case if possible. Mike, would it be fine if we
> > > go back to /dev/hugepages path based approach in the test case?
> >
> > One possible alternative, can we use memfd_create() with MFD_HUGE_*?
> > This afaict lets us have an fd so we can create two mappings,
> > without having to mount hugetlbfs, pass in a path to the test, ...
>
> Sounds good. :) We can also rework the shared hugetlb too. Wanna post a
> patch? I can do that too, let me know otherwise. Thanks!

Sure, I'll take a whack at it.

>
> --
> Peter Xu
>

\
 
 \ /
  Last update: 2022-07-15 19:54    [W:0.110 / U:1.860 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site