From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: 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.
Previously, when KASAN had detected an error on an object from a cache
with SLAB_RED_ZONE set, the actual start address of the object was
miscalculated, which led to random stacks having been reported.
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")
Link: http://lkml.kernel.org/r/1468347165-41906-2-git-send-email-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <adech.fo@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Steven Rostedt (Red Hat) <rostedt@xxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Kostya Serebryany <kcc@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Kuthonuzo Luruo <kuthonuzo.luruo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/slub_def.h | 10 ++++++----
mm/slub.c | 2 +-
2 files changed, 7 insertions(+), 5 deletions(-)
diff -puN include/linux/slub_def.h~mm-kasan-account-for-object-redzone-in-slubs-nearest_obj include/linux/slub_def.h
--- a/include/linux/slub_def.h~mm-kasan-account-for-object-redzone-in-slubs-nearest_obj
+++ a/include/linux/slub_def.h
@@ -119,15 +119,17 @@ static inline void sysfs_slab_remove(str
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 -puN mm/slub.c~mm-kasan-account-for-object-redzone-in-slubs-nearest_obj mm/slub.c
--- a/mm/slub.c~mm-kasan-account-for-object-redzone-in-slubs-nearest_obj
+++ a/mm/slub.c
@@ -124,7 +124,7 @@ static inline int kmem_cache_debug(struc
#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;
_
--
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