[PATCH] mm/huge_memory: update file PUD counter before folio_put()

[Yin Tirui]

__split_huge_pud_locked() updates the file/shmem RSS counter after
dropping the PUD mapping's folio reference. If folio_put() drops the
last reference, mm_counter_file() can later read freed folio state via
folio_test_swapbacked().

Move the counter update before folio_put().

Fixes: dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Yin Tirui <yintirui@xxxxxxxxxx>
---
 mm/huge_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a5f4a48b7b77..9832ee910d5e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3027,9 +3027,9 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
 	if (!folio_test_referenced(folio) && pud_young(old_pud))
 		folio_set_referenced(folio);
 	folio_remove_rmap_pud(folio, page, vma);
-	folio_put(folio);
 	add_mm_counter(vma->vm_mm, mm_counter_file(folio),
 		-HPAGE_PUD_NR);
+	folio_put(folio);
 }
 
 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
-- 
2.43.0