On 08.09.22 04:47, HORIGUCHI NAOYA(堀口 直也) wrote:
On Wed, Sep 07, 2022 at 01:57:45PM -0700, Andrew Morton wrote:
On Wed, 7 Sep 2022 21:11:57 +0900 Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx> wrote:
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")
January of 2016! Or was this a long-term bug which was recently
exposed by some other change?
Maybe yes, I confirmed that this issue reproduces in kernel 5.10 (released
on Dec 13, 2020, which might not be so "recent"), but does not reproduce in
kernel 5.4. So I think that marking "5.10+" for stable is fine.
I fixed plenty of such issues in the past. For example:
aad5f69bc161 ("fs/proc/page.c: don't access uninitialized memmaps in fs/proc/page.c")
This one just wasn't found so far because it's triggered via
a debug interface.
The correct fixes tag would be:
Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") [visible after d0dc12e86b319]
Exposed "recently" -- 2018 ;)
--
Thanks,
David / dhildenb
