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, 0 insertions, 2 deletions

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 4852625ff851..7fd121d13b88 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -144,13 +144,11 @@ static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
 static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
 {
         void *object = qlink_to_object(qlink, cache);
-        struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
         unsigned long flags;
 
         if (IS_ENABLED(CONFIG_SLAB))
                 local_irq_save(flags);
 
-        alloc_info->state = KASAN_STATE_FREE;
         ___cache_free(cache, object, _THIS_IP_);
 
         if (IS_ENABLED(CONFIG_SLAB))