On 10/15/19 5:07 AM, 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> Thanks David, Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> -- Mike Kravetz
