[PATCH RFC v2 19/21] kasan: don't round_up too much

From: Andrey Konovalov
Date: Thu Oct 22 2020 - 09:21:01 EST


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

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Link: https://linux-review.googlesource.com/id/Ib397128fac6eba874008662b4964d65352db4aa4
---
mm/kasan/common.c | 8 ++------
mm/kasan/shadow.c | 1 +
2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 5622b0ec0907..983383ebe32a 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -215,9 +215,7 @@ void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)

void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
{
- kasan_poison_memory(object,
- round_up(cache->object_size, KASAN_GRANULE_SIZE),
- KASAN_KMALLOC_REDZONE);
+ kasan_poison_memory(object, cache->object_size, KASAN_KMALLOC_REDZONE);
}

/*
@@ -290,7 +288,6 @@ 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;
@@ -311,8 +308,7 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
return true;
}

- rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
- kasan_poison_memory(object, rounded_up_size, KASAN_KMALLOC_FREE);
+ kasan_poison_memory(object, cache->object_size, KASAN_KMALLOC_FREE);

if (static_branch_unlikely(&kasan_stack)) {
if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 616ac64c4a21..ab1d39c566b9 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -82,6 +82,7 @@ void kasan_poison_memory(const void *address, size_t size, u8 value)
* addresses to this function.
*/
address = 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);
--
2.29.0.rc1.297.gfa9743e501-goog