The commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra
allocated kmalloc space than requested") will extend right redzone
when allocating for orig_size < object_size. So we can't overlay the
freepointer in the object space in this case.
But the code looks like it forgot to check SLAB_RED_ZONE, since there
won't be extended right redzone if only orig_size enabled.
As we are here, make this complex conditional expressions a little
prettier and add some comments about extending right redzone when
slub_debug_orig_size() enabled.
Reviewed-by: Feng Tang <feng.tang@xxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Chengming Zhou <chengming.zhou@xxxxxxxxx>
---
mm/slub.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 45f89d4bb687..1551a0345650 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5169,10 +5169,9 @@ static int calculate_sizes(struct kmem_cache *s)
*/
s->inuse = size;
- if (slub_debug_orig_size(s) ||
- (flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
- ((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) ||
- s->ctor) {
+ if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || s->ctor ||
+ ((flags & SLAB_RED_ZONE) &&
+ (s->object_size < sizeof(void *) || slub_debug_orig_size(s)))) {
/*
* Relocate free pointer after the object if it is not
* permitted to overwrite the first word of the object on
@@ -5180,7 +5179,9 @@ static int calculate_sizes(struct kmem_cache *s)
*
* This is the case if we do RCU, have a constructor or
* destructor, are poisoning the objects, or are
- * redzoning an object smaller than sizeof(void *).
+ * redzoning an object smaller than sizeof(void *) or are
+ * redzoning an object with slub_debug_orig_size() enabled,
+ * in which case the right redzone may be extended.
*
* The assumption that s->offset >= s->inuse means free
* pointer is outside of the object is used in the
--
2.45.1
