[PATCH 4.19 22/37] mm, slub: fix mismatch between reconstructed freelist depth and cnt

[Greg Kroah-Hartman]

From: Miaohe Lin <linmiaohe@xxxxxxxxxx>

commit 899447f669da76cc3605665e1a95ee877bc464cc upstream.

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() complaining about freelist count or a
incorrect slub inuse count.

Link: https://lkml.kernel.org/r/20210916123920.48704-3-linmiaohe@xxxxxxxxxx
Fixes: c3895391df38 ("kasan, slub: fix handling of kasan_slab_free hook")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Bharata B Rao <bharata@xxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Faiyaz Mohammed <faiyazm@xxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/slub.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1392,7 +1392,8 @@ static __always_inline bool slab_free_ho
 }
 
 static inline bool slab_free_freelist_hook(struct kmem_cache *s,
-					   void **head, void **tail)
+					   void **head, void **tail,
+					   int *cnt)
 {
 /*
  * Compiler cannot detect this function can be removed if slab_free_hook()
@@ -1421,6 +1422,12 @@ static inline bool slab_free_freelist_ho
 			*head = object;
 			if (!*tail)
 				*tail = object;
+		} else {
+			/*
+			 * Adjust the reconstructed freelist depth
+			 * accordingly if object's reuse is delayed.
+			 */
+			--(*cnt);
 		}
 	} while (object != old_tail);
 
@@ -2988,7 +2995,7 @@ static __always_inline void slab_free(st
 	 * 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);
 }