linux-kernel - [PATCH v8 2/3] mm, kasan: align free_meta

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Message-Id: <1469719879-11761-3-git-send-email-glider@google.com>
Date:	Thu, 28 Jul 2016 17:31:18 +0200
From:	Alexander Potapenko <glider@...gle.com>
To:	dvyukov@...gle.com, kcc@...gle.com, aryabinin@...tuozzo.com,
	adech.fo@...il.com, cl@...ux.com, akpm@...ux-foundation.org,
	rostedt@...dmis.org, js1304@...il.com, iamjoonsoo.kim@....com,
	kuthonuzo.luruo@....com
Cc:	kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH v8 2/3] mm, kasan: align free_meta_offset on sizeof(void*)

When free_meta_offset is not zero, it is usually aligned on 4 bytes,
because the size of preceding kasan_alloc_meta is aligned on 4 bytes.
As a result, accesses to kasan_free_meta fields may be misaligned.

Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 mm/kasan/kasan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 6845f92..0379551 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -390,7 +390,8 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size,
 	/* Add free meta. */
 	if (cache->flags & SLAB_DESTROY_BY_RCU || cache->ctor ||
 	    cache->object_size < sizeof(struct kasan_free_meta)) {
-		cache->kasan_info.free_meta_offset = *size;
+		cache->kasan_info.free_meta_offset =
+			ALIGN(*size, sizeof(void *));
 		*size += sizeof(struct kasan_free_meta);
 	}
 	redzone_adjust = optimal_redzone(cache->object_size) -
-- 
2.8.0.rc3.226.g39d4020