On Thu 27-05-21 09:28:51, Mike Kravetz wrote:
> On 5/26/21 4:52 PM, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> >
> > When memory_failure() or soft_offline_page() is called on a tail page of
> > some hugetlb page, "BUG: unable to handle page fault" error can be
> > triggered.
> >
> > remove_hugetlb_page() dereferences page->lru, so it's assumed that the
> > page points to a head page, but one of the caller,
> > dissolve_free_huge_page(), provides remove_hugetlb_page() with 'page'
> > which could be a tail page. So pass 'head' to it, instead.
> >
> > Fixes: 6eb4e88a6d27 ("hugetlb: create remove_hugetlb_page() to separate functionality")
> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > ---
> > mm/hugetlb.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git v5.13-rc3/mm/hugetlb.c v5.13-rc3_patched/mm/hugetlb.c
> > index 95918f410c0f..470f7b5b437e 100644
> > --- v5.13-rc3/mm/hugetlb.c
> > +++ v5.13-rc3_patched/mm/hugetlb.c
> > @@ -1793,7 +1793,7 @@ int dissolve_free_huge_page(struct page *page)
> > SetPageHWPoison(page);
> > ClearPageHWPoison(head);
> > }
> > - remove_hugetlb_page(h, page, false);
> > + remove_hugetlb_page(h, head, false);
> > h->max_huge_pages--;
> > spin_unlock_irq(&hugetlb_lock);
> > update_and_free_page(h, head);
> >
>
> I believe we have the same problem later in the routine when calling
> add_hugetlb_page()?
Can we ever get a tail page there?
> If so, should we combine the changes? Or, do we need two patches as
> the bugs were introduced with different commits?
If there is an issue then I would go with a separate patch.
Thanks!
--
Michal Hocko
SUSE Labs
