Re: [syzbot] BUG: unable to handle kernel paging request in alloc_huge_page

[Dmitry Vyukov]

On Sun, 15 Aug 2021 at 20:17, Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
>
> On 8/14/21 4:24 PM, Matthew Wilcox wrote:
> > On Sat, Aug 14, 2021 at 03:06:52PM -0700, Andrew Morton wrote:
> >> On Sat, 14 Aug 2021 04:07:23 -0700 syzbot <syzbot+57876cfc2dca0c6b2e6a@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>> HEAD commit:    92d00774360d Add linux-next specific files for 20210810
> >>> RIP: 0010:__list_add include/linux/list.h:71 [inline]
> >>> RIP: 0010:list_add include/linux/list.h:86 [inline]
> >>> RIP: 0010:alloc_huge_page+0xdcb/0x11b0 mm/hugetlb.c:2821
> >>
> >> That appears to be
> >>
> >>              list_add(&page->lru, &h->hugepage_activelist);
> >>
> >> I'm suspecting Mike's surplus page changes?
> >
> > Is this not the same as
> > https://lore.kernel.org/linux-mm/846c4502-3332-0d25-87f5-cb3b71afc38f@xxxxxxxxxxx/
> > which is already patched in your tree?
>
> Yes, I believe it is the same, and already fixed.  RCX: fffffffffffffffc
> makes me 99.9% confident.

Let's tell syzbot about the fix:

#syz fix:
mm/hugetlb: Initialize page to NULL in alloc_buddy_huge_page_with_mpol()