Commit c146a2b9 authored Jul 28, 2016 by Alexander Potapenko Committed by Linus Torvalds Jul 28, 2016

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: 7ed2f9e6 ("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>

parent 734537c9

include/linux/slub_def.h

+6 −4

Original line number	Diff line number	Diff line
		@@ -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 */

mm/slub.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

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