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>
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 388e812..92750e3 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -442,11 +442,6 @@
kasan_poison_shadow(object,
round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
KASAN_KMALLOC_REDZONE);
- if (cache->flags & SLAB_KASAN) {
- struct kasan_alloc_meta *alloc_info =
- get_alloc_info(cache, object);
- alloc_info->state = KASAN_STATE_INIT;
- }
}
static inline int in_irqentry_text(unsigned long ptr)
@@ -510,6 +505,17 @@
return (void *)object + cache->kasan_info.free_meta_offset;
}
+void kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
+{
+ struct kasan_alloc_meta *alloc_info;
+
+ if (!(cache->flags & SLAB_KASAN))
+ return;
+
+ alloc_info = get_alloc_info(cache, object);
+ __memset(alloc_info, 0, sizeof(*alloc_info));
+}
+
void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
{
kasan_kmalloc(cache, object, cache->object_size, flags);
@@ -529,34 +535,27 @@
bool kasan_slab_free(struct kmem_cache *cache, void *object)
{
+ s8 shadow_byte;
+
/* RCU slabs could be legally used after free within the RCU period */
if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
return false;
- if (likely(cache->flags & SLAB_KASAN)) {
- struct kasan_alloc_meta *alloc_info;
- struct kasan_free_meta *free_info;
-
- alloc_info = get_alloc_info(cache, object);
- free_info = get_free_info(cache, object);
-
- switch (alloc_info->state) {
- case KASAN_STATE_ALLOC:
- alloc_info->state = KASAN_STATE_QUARANTINE;
- set_track(&free_info->track, GFP_NOWAIT);
- kasan_poison_slab_free(cache, object);
- quarantine_put(free_info, cache);
- return true;
- case KASAN_STATE_QUARANTINE:
- case KASAN_STATE_FREE:
- pr_err("Double free");
- dump_stack();
- break;
- default:
- break;
- }
+ shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
+ if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
+ pr_err("Double free");
+ dump_stack();
+ return true;
}
- return false;
+
+ kasan_poison_slab_free(cache, object);
+
+ if (unlikely(!(cache->flags & SLAB_KASAN)))
+ return false;
+
+ set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
+ quarantine_put(get_free_info(cache, object), cache);
+ return true;
}
void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
@@ -579,13 +578,9 @@
kasan_unpoison_shadow(object, size);
kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
KASAN_KMALLOC_REDZONE);
- if (cache->flags & SLAB_KASAN) {
- struct kasan_alloc_meta *alloc_info =
- get_alloc_info(cache, object);
- alloc_info->state = KASAN_STATE_ALLOC;
- set_track(&alloc_info->track, flags);
- }
+ if (cache->flags & SLAB_KASAN)
+ set_track(&get_alloc_info(cache, object)->alloc_track, flags);
}
EXPORT_SYMBOL(kasan_kmalloc);