[PATCH 2/5] mm, slub: fix mismatch between reconstructed freelist depth and cnt

[Miaohe Lin]

If object's reuse is delayed, it will be excluded from the reconstructed
freelist. But we forgot to adjust the cnt accordingly. So there will be
a mismatch between reconstructed freelist depth and cnt. This will lead
to free_debug_processing() complain about freelist count or a incorrect
slub inuse count.

Fixes: c3895391df38 ("kasan, slub: fix handling of kasan_slab_free hook")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
 mm/slub.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index ed160b6c54f8..a56a6423d4e8 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1701,7 +1701,8 @@ static __always_inline bool slab_free_hook(struct kmem_cache *s,
 }
 
 static inline bool slab_free_freelist_hook(struct kmem_cache *s,
-					   void **head, void **tail)
+					   void **head, void **tail,
+					   int *cnt)
 {
 
 	void *object;
@@ -1728,6 +1729,12 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
 			*head = object;
 			if (!*tail)
 				*tail = object;
+		} else {
+			/*
+			 * Adjust the reconstructed freelist depth
+			 * accordingly if object's reuse is delayed.
+			 */
+			--(*cnt);
 		}
 	} while (object != old_tail);
 
@@ -3480,7 +3487,7 @@ static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
 	 * With KASAN enabled slab_free_freelist_hook modifies the freelist
 	 * to remove objects, whose reuse must be delayed.
 	 */
-	if (slab_free_freelist_hook(s, &head, &tail))
+	if (slab_free_freelist_hook(s, &head, &tail, &cnt))
 		do_slab_free(s, page, head, tail, cnt, addr);
 }
 
-- 
2.23.0