On Tue 15-10-19 14:07:17, David Hildenbrand wrote: > Uninitialized memmaps contain garbage and in the worst case trigger > kernel BUGs, especially with CONFIG_PAGE_POISONING. They should not get > touched. > > Let's make sure that we only consider online memory (managed by the > buddy) that has initialized memmaps. ZONE_DEVICE is not applicable. > > page_zone() will call page_to_nid(), which will trigger > VM_BUG_ON_PGFLAGS(PagePoisoned(page), page) with CONFIG_PAGE_POISONING > and CONFIG_DEBUG_VM_PGFLAGS when called on uninitialized memmaps. This > can be the case when an offline memory block (e.g., never onlined) is > spanned by a zone. > > Note: As explained by Michal in [1], alloc_contig_range() will verify > the range. So it boils down to the wrong access in this function. > > [1] http://lkml.kernel.org/r/20180423000943.GO17484@xxxxxxxxxxxxxx > > Reported-by: Michal Hocko <mhocko@xxxxxxxxxx> > Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319 > Cc: stable@xxxxxxxxxxxxxxx # v4.13+ > Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx> > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks! > --- > mm/hugetlb.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index ef37c85423a5..b45a95363a84 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1084,11 +1084,10 @@ static bool pfn_range_valid_gigantic(struct zone *z, > struct page *page; > > for (i = start_pfn; i < end_pfn; i++) { > - if (!pfn_valid(i)) > + page = pfn_to_online_page(i); > + if (!page) > return false; > > - page = pfn_to_page(i); > - > if (page_zone(page) != z) > return false; > > -- > 2.21.0 -- Michal Hocko SUSE Labs
