[PATCH v2 16/20] kasan: simplify assign_tag and set_tag calls

From: Andrey Konovalov
Date: Tue Nov 10 2020 - 17:21:22 EST


set_tag() already ignores the tag for the generic mode, so just call it
as is. Add a check for the generic mode to assign_tag(), and simplify its
call in ____kasan_kmalloc().

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Link: https://linux-review.googlesource.com/id/I18905ca78fb4a3d60e1a34a4ca00247272480438
---
mm/kasan/common.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69ab880abacc..40ff3ce07a76 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -238,6 +238,9 @@ void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
static u8 assign_tag(struct kmem_cache *cache, const void *object,
bool init, bool keep_tag)
{
+ if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+ return 0xff;
+
/*
* 1. When an object is kmalloc()'ed, two hooks are called:
* kasan_slab_alloc() and kasan_kmalloc(). We assign the
@@ -280,8 +283,8 @@ void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
__memset(alloc_meta, 0, sizeof(*alloc_meta));
}

- if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
- object = set_tag(object, assign_tag(cache, object, true, false));
+ /* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
+ object = set_tag(object, assign_tag(cache, object, true, false));

return (void *)object;
}
@@ -362,9 +365,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
KASAN_GRANULE_SIZE);
redzone_end = round_up((unsigned long)object + cache->object_size,
KASAN_GRANULE_SIZE);
-
- if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
- tag = assign_tag(cache, object, false, keep_tag);
+ tag = assign_tag(cache, object, false, keep_tag);

/* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */
kasan_unpoison_memory(set_tag(object, tag), size);
--
2.29.2.222.g5d2a92d10f8-goog