The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

2b7aa91ba0e8 ("mm/huge_memory: use pfn_to_online_page() in split_huge_pages_all()") a17206dac7b2 ("mm/huge_memory: minor cleanup for split_huge_pages_all") fa6c02315f74 ("mm: huge_memory: a new debugfs interface for splitting THP tests") f3a45709d2bb ("selftests/vm: hmm-tests: remove the libhugetlbfs dependency") f545605cc08e ("selftests/vm: minor cleanup: Makefile and gup_test.c") b9dcfdff8b4b ("selftests/vm: use a common gup_test.h") 9c84f229268f ("mm/gup_benchmark: rename to mm/gup_test")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2b7aa91ba0e86b8643f5d3c83874c80599c731d7 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi naoya.horiguchi@nec.com Date: Thu, 8 Sep 2022 13:11:50 +0900 Subject: [PATCH] mm/huge_memory: use pfn_to_online_page() in split_huge_pages_all()

NULL pointer dereference is triggered when calling thp split via debugfs on the system with offlined memory blocks. With debug option enabled, the following kernel messages are printed out:

page:00000000467f4890 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121c000 flags: 0x17fffc00000000(node=0|zone=2|lastcpupid=0x1ffff) raw: 0017fffc00000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 page dumped because: unmovable page page:000000007d7ab72e is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) ------------[ cut here ]------------ kernel BUG at include/linux/mm.h:1248! invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 16 PID: 20964 Comm: bash Tainted: G I 6.0.0-rc3-foll-numa+ #41 ... RIP: 0010:split_huge_pages_write+0xcf4/0xe30

This shows that page_to_nid() in page_zone() is unexpectedly called for an offlined memmap.

Use pfn_to_online_page() to get struct page in PFN walker.

Link: https://lkml.kernel.org/r/20220908041150.3430269-1-naoya.horiguchi@linux.dev Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") [visible after d0dc12e86b319] Signed-off-by: Naoya Horiguchi naoya.horiguchi@nec.com Co-developed-by: David Hildenbrand david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Yang Shi shy828301@gmail.com Acked-by: Michal Hocko mhocko@suse.com Reviewed-by: Miaohe Lin linmiaohe@huawei.com Reviewed-by: Oscar Salvador osalvador@suse.de Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Matthew Wilcox willy@infradead.org Cc: Muchun Song songmuchun@bytedance.com Cc: stable@vger.kernel.org [5.10+] Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e9414ee57c5b..f42bb51e023a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2894,11 +2894,9 @@ static void split_huge_pages_all(void) max_zone_pfn = zone_end_pfn(zone); for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { int nr_pages; - if (!pfn_valid(pfn)) - continue;

- page = pfn_to_page(pfn); - if (!get_page_unless_zero(page)) + page = pfn_to_online_page(pfn); + if (!page || !get_page_unless_zero(page)) continue;

if (zone != page_zone(page))