linux-kernel - [PATCH v7 1/2] mm, kasan: account for object redzone in SLUB's nearest

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Message-Id: <1468347165-41906-2-git-send-email-glider@google.com>
Date:	Tue, 12 Jul 2016 20:12:44 +0200
From:	Alexander Potapenko <glider@...gle.com>
To:	adech.fo@...il.com, cl@...ux.com, dvyukov@...gle.com,
	akpm@...ux-foundation.org, rostedt@...dmis.org,
	iamjoonsoo.kim@....com, js1304@...il.com, kcc@...gle.com,
	aryabinin@...tuozzo.com, kuthonuzo.luruo@....com
Cc:	kasan-dev@...glegroups.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v7 1/2] mm, kasan: account for object redzone in SLUB's nearest_obj()

When looking up the nearest SLUB object for a given address, correctly
calculate its offset if SLAB_RED_ZONE is enabled for that cache.

Fixes: 7ed2f9e663854db ("mm, kasan: SLAB support")
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 include/linux/slub_def.h | 10 ++++++----
 mm/slub.c                |  2 +-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index d1faa01..b71b258 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -114,15 +114,17 @@ static inline void sysfs_slab_remove(struct kmem_cache *s)
 void object_err(struct kmem_cache *s, struct page *page,
 		u8 *object, char *reason);
 
+void *fixup_red_left(struct kmem_cache *s, void *p);
+
 static inline void *nearest_obj(struct kmem_cache *cache, struct page *page,
 				void *x) {
 	void *object = x - (x - page_address(page)) % cache->size;
 	void *last_object = page_address(page) +
 		(page->objects - 1) * cache->size;
-	if (unlikely(object > last_object))
-		return last_object;
-	else
-		return object;
+	void *result = (unlikely(object > last_object)) ? last_object : object;
+
+	result = fixup_red_left(cache, result);
+	return result;
 }
 
 #endif /* _LINUX_SLUB_DEF_H */
diff --git a/mm/slub.c b/mm/slub.c
index 825ff45..27cbef9 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -124,7 +124,7 @@ static inline int kmem_cache_debug(struct kmem_cache *s)
 #endif
 }
 
-static inline void *fixup_red_left(struct kmem_cache *s, void *p)
+inline void *fixup_red_left(struct kmem_cache *s, void *p)
 {
 	if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
 		p += s->red_left_pad;
-- 
2.8.0.rc3.226.g39d4020