kasan: don't round_up too much

For hardware tag-based mode kasan_poison_memory() already rounds up the
size. Do the same for software modes and remove round_up() from the common
code.

Link: https://lkml.kernel.org/r/47b232474f1f89dc072aeda0fa58daa6efade377.1606162397.git.andreyknvl@google.com
Link: https://linux-review.googlesource.com/id/Ib397128fac6eba874008662b4964d65352db4aa4
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/kasan/common.c

@@ -213,9 +213,7 @@ void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 
 void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
 {
-	poison_range(object,
-			round_up(cache->object_size, KASAN_GRANULE_SIZE),
-			KASAN_KMALLOC_REDZONE);
+	poison_range(object, cache->object_size, KASAN_KMALLOC_REDZONE);
 }
 
 /*
@@ -288,7 +286,6 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
 {
 	u8 tag;
 	void *tagged_object;
-	unsigned long rounded_up_size;
 
 	tag = get_tag(object);
 	tagged_object = object;
@@ -309,8 +306,7 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
 		return true;
 	}
 
-	rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
-	poison_range(object, rounded_up_size, KASAN_KMALLOC_FREE);
+	poison_range(object, cache->object_size, KASAN_KMALLOC_FREE);
 
 	if (!kasan_stack_collection_enabled())
 		return false;

mm/kasan/shadow.c

@@ -82,6 +82,7 @@ void poison_range(const void *address, size_t size, u8 value)
 	 * addresses to this function.
 	 */
 	address = kasan_reset_tag(address);
+	size = round_up(size, KASAN_GRANULE_SIZE);
 
 	shadow_start = kasan_mem_to_shadow(address);
 	shadow_end = kasan_mem_to_shadow(address + size);