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/[email protected] Reported-by: Michal Hocko <[email protected]> Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319 Cc: [email protected] # v4.13+ Cc: Anshuman Khandual <[email protected]> Cc: Mike Kravetz <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Michal Hocko <[email protected]> Signed-off-by: David Hildenbrand <[email protected]> --- 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
