[PATCH 5.4 39/58] mm, slub: fix mismatch between reconstructed freelist depth and cnt

From: Greg Kroah-Hartman
Date: Mon Oct 25 2021 - 15:38:59 EST


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
@@ -1455,7 +1455,8 @@ 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)
{

void *object;
@@ -1490,6 +1491,12 @@ 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);

@@ -3049,7 +3056,7 @@ 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);
}