Commit f231fe42 authored by David Hildenbrand's avatar David Hildenbrand Committed by Linus Torvalds

hugetlbfs: don't access uninitialized memmaps in pfn_range_valid_gigantic()

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@dhcp22.suse.cz

Link: http://lkml.kernel.org/r/20191015120717.4858-1-david@redhat.com
Fixes: f1dd2cd1 ("mm, memory_hotplug: do not associate hotadded memory to zones until online")	[visible after d0dc12e8]
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reported-by: default avatarMichal Hocko <mhocko@kernel.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: <stable@vger.kernel.org>	[4.13+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f3057ad7
...@@ -1084,11 +1084,10 @@ static bool pfn_range_valid_gigantic(struct zone *z, ...@@ -1084,11 +1084,10 @@ static bool pfn_range_valid_gigantic(struct zone *z,
struct page *page; struct page *page;
for (i = start_pfn; i < end_pfn; i++) { for (i = start_pfn; i < end_pfn; i++) {
if (!pfn_valid(i)) page = pfn_to_online_page(i);
if (!page)
return false; return false;
page = pfn_to_page(i);
if (page_zone(page) != z) if (page_zone(page) != z)
return false; return false;
......
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