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commit f231fe4235e22e18d847e05cbe705deaca56580a upstream. 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: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") [visible after d0dc12e86b319] Signed-off-by: David Hildenbrand <david@redhat.com> Reported-by: Michal Hocko <mhocko@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: <stable@vger.kernel.org> [4.13+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.