The patch titled
Subject: slub: choose the right freelist pointer location when creating small caches
has been added to the -mm tree. Its filename is
slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch
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------------------------------------------------------
From: "Lin, Zhenpeng" <zplin@xxxxxxx>
Subject: slub: choose the right freelist pointer location when creating small caches
When enabling CONFIG_SLUB_DEBUG and booting with "slub_debug=Z", the
kernel crashes at creating caches if the object size is smaller than
2*sizeof(void*). The problem is due to the wrong calculation of
freepointer_area. The freelist pointer can be stored in the middle of
object only if the object size is not smaller than 2*sizeof(void*).
Otherwise, the freelist pointer will be corrupted by SLUB_RED_ZONE.
Link: https://lkml.kernel.org/r/6746FEEA-FD69-4792-8DDA-C78F5FE7DA02@xxxxxxx
Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object")
Fixes: 89b83f282d8b ("slub: avoid redzone when choosing freepointer location")
Signed-off-by: Zhenpeng Lin <zplin@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/slub.c~slub-choose-the-right-freelist-pointer-location-when-creating-small-caches
+++ a/mm/slub.c
@@ -3752,7 +3752,7 @@ static int calculate_sizes(struct kmem_c
* can't use that portion for writing the freepointer, so
* s->offset must be limited within this for the general case.
*/
- freepointer_area = size;
+ freepointer_area = s->object_size;
#ifdef CONFIG_SLUB_DEBUG
/*
@@ -3799,7 +3799,7 @@ static int calculate_sizes(struct kmem_c
*/
s->offset = size;
size += sizeof(void *);
- } else if (freepointer_area > sizeof(void *)) {
+ } else if (freepointer_area > 2 * sizeof(void *)) {
/*
* Store freelist pointer near middle of object to keep
* it away from the edges of the object to avoid small
_
Patches currently in -mm which might be from zplin@xxxxxxx are
slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch
