On Wed 07-09-22 21:11:57, Naoya Horiguchi wrote:
[...]
> >From 8a5c284df732943065d23838090d15c94cd10395 Mon Sep 17 00:00:00 2001
> From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> Date: Wed, 7 Sep 2022 20:58:44 +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.
>
> Fixes: 49071d436b51 ("thp: add debugfs handle to split all huge pages")
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
With changes proposed by David
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> mm/huge_memory.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 5fa2ba86dae4..03149a8f46f9 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2894,11 +2894,8 @@ 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))
> --
> 2.26.1.8815.g6a475b71f8
>
--
Michal Hocko
SUSE Labs
