mm/kasan: get rid of ->state in struct kasan_alloc_meta

The state of object currently tracked in two places - shadow memory, and
the ->state field in struct kasan_alloc_meta.  We can get rid of the
latter.  The will save us a little bit of memory.  Also, this allow us
to move free stack into struct kasan_alloc_meta, without increasing
memory consumption.  So now we should always know when the last time the
object was freed.  This may be useful for long delayed use-after-free
bugs.

As a side effect this fixes following UBSAN warning:
	UBSAN: Undefined behaviour in mm/kasan/quarantine.c:102:13
	member access within misaligned address ffff88000d1efebc for type 'struct qlist_node'
	which requires 8 byte alignment

Link: http://lkml.kernel.org/r/1470062715-14077-5-git-send-email-aryabinin@virtuozzo.com
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 09771ed..ca135bd 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2604,9 +2604,11 @@ static void cache_init_objs(struct kmem_cache *cachep,
 	}
 
 	for (i = 0; i < cachep->num; i++) {
+		objp = index_to_obj(cachep, page, i);
+		kasan_init_slab_obj(cachep, objp);
+
 		/* constructor could break poison info */
 		if (DEBUG == 0 && cachep->ctor) {
-			objp = index_to_obj(cachep, page, i);
 			kasan_unpoison_object_data(cachep, objp);
 			cachep->ctor(objp);
 			kasan_poison_object_data(cachep, objp);