[PATCH v3] mm/memory-failure: fix crash in split_huge_page_to_list from soft_offline_page

[Miaohe Lin]

When I did soft offline stress test, a machine was observed to crash with
the following message:

  kernel BUG at include/linux/memcontrol.h:554!
  invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 5 PID: 3837 Comm: hwpoison.sh Not tainted 6.7.0-next-20240112-00001-g8ecf3e7fb7c8-dirty #97
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
  RIP: 0010:folio_memcg+0xaf/0xd0
  Code: 10 5b 5d c3 cc cc cc cc 48 c7 c6 08 b1 f2 b2 48 89 ef e8 b4 c5 f8 ff 90 0f 0b 48 c7 c6 d0 b0 f2 b2 48 89 ef e8 a2 c5 f8 ff 90 <0f> 0b 48 c7 c6 08 b1 f2 b2 48 89 ef e8 90 c5 f8 ff 90 0f 0b 66 66
  RSP: 0018:ffffb6c043657c98 EFLAGS: 00000296
  RAX: 000000000000004b RBX: ffff932bc1d1e401 RCX: ffff933abfb5c908
  RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff933abfb5c900
  RBP: ffffea6f04019080 R08: ffffffffb3338ce8 R09: 0000000000009ffb
  R10: 00000000000004dd R11: ffffffffb3308d00 R12: ffffea6f04019080
  R13: ffffea6f04019080 R14: 0000000000000001 R15: ffffb6c043657da0
  FS:  00007f6c60f6b740(0000) GS:ffff933abfb40000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000559c3bc8b980 CR3: 0000000107f1c000 CR4: 00000000000006f0
  Call Trace:
   <TASK>
   split_huge_page_to_list+0x4d/0x1380
   try_to_split_thp_page+0x3a/0xf0
   soft_offline_page+0x1ea/0x8a0
   soft_offline_page_store+0x52/0x90
   kernfs_fop_write_iter+0x118/0x1b0
   vfs_write+0x30b/0x430
   ksys_write+0x5e/0xe0
   do_syscall_64+0xb0/0x1b0
   entry_SYSCALL_64_after_hwframe+0x6d/0x75
  RIP: 0033:0x7f6c60d14697
  Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
  RSP: 002b:00007ffe9b72b8d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
  RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007f6c60d14697
  RDX: 000000000000000c RSI: 0000559c3bc8b980 RDI: 0000000000000001
  RBP: 0000559c3bc8b980 R08: 00007f6c60dd1460 R09: 000000007fffffff
  R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000c
  R13: 00007f6c60e1a780 R14: 00007f6c60e16600 R15: 00007f6c60e15a00

The problem is that page->mapping is overloaded with slab->slab_list or
slabs fields now, so slab pages could be taken as non-LRU movable pages
if field slabs contains PAGE_MAPPING_MOVABLE or slab_list->prev is set
to LIST_POISON2. These slab pages will be treated as thp later leading
to crash in split_huge_page_to_list().

Fixes: 130d4df57390 ("mm/sl[au]b: rearrange struct slab fields to allow larger rcu_head")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
v3:
  Trim those '?' lines out of the backtrace per Matthew.
  Collect Reviewed-by tag from Matthew. Thanks.
v2:
  Check PageSlab() first to leave the rest code alone per Matthew.
---
 mm/memory-failure.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 636280d04008..9349948f1abf 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1377,6 +1377,9 @@ void ClearPageHWPoisonTakenOff(struct page *page)
  */
 static inline bool HWPoisonHandlable(struct page *page, unsigned long flags)
 {
+	if (PageSlab(page))
+		return false;
+
 	/* Soft offline could migrate non-LRU movable pages */
 	if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))
 		return true;
-- 
2.33.0