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Subject[PATCH v4 3/3] kasan: add memory corruption identification support for hardware tag-based mode
Date
Add memory corruption identification support for hardware tag-based
mode. We store one old free pointer tag and free backtrace instead
of five because hardware tag-based kasan only has 16 different tags.

If we store as many stacks as SW tag-based kasan does(5 stacks),
there is high probability to find the same tag in the stacks when
out-of-bound issues happened and we will mistake out-of-bound
issue for use-after-free.

Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Suggested-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
lib/Kconfig.kasan | 2 +-
mm/kasan/kasan.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index fdb4a08dba83..1e2d10f86011 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -169,7 +169,7 @@ config KASAN_STACK

config KASAN_TAGS_IDENTIFY
bool "Enable memory corruption identification"
- depends on KASAN_SW_TAGS
+ depends on KASAN_SW_TAGS || KASAN_HW_TAGS
help
This option enables best-effort identification of bug type
(use-after-free or out-of-bounds) at the cost of increased
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 952df2db7fdd..f58672f6029a 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -153,7 +153,7 @@ struct kasan_track {
depot_stack_handle_t stack;
};

-#ifdef CONFIG_KASAN_TAGS_IDENTIFY
+#if defined(CONFIG_KASAN_TAGS_IDENTIFY) && defined(CONFIG_KASAN_SW_TAGS)
#define KASAN_NR_FREE_STACKS 5
#else
#define KASAN_NR_FREE_STACKS 1
--
2.18.0
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