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mm, kasan: account for object redzone in SLUB's nearest_obj()

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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: 7ed2f9e663 ("mm, kasan: SLAB support")
Link: http://lkml.kernel.org/r/1468347165-41906-2-git-send-email-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Kuthonuzo Luruo <kuthonuzo.luruo@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexander Potapenko 2016-07-28 15:49:04 -07:00 committed by Linus Torvalds
parent 734537c9cb
commit c146a2b98e
2 changed files with 7 additions and 5 deletions
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10
include/linux/slub_def.h
View File

@ -119,15 +119,17 @@ 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 */

2
mm/slub.c
View File

@ -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;