Provide a helper that will perform wrapping addition without tripping
the arithmetic wrap-around sanitizers.
Cc: "Gustavo A. R. Silva" <gustavo...@kernel.org>
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
include/linux/overflow.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index ac088f73e0fd..30779905a77a 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -124,6 +124,22 @@ static inline bool __must_check __must_check_overflow(bool
overflow)
check_add_overflow(a, b, &__result);\
}))
+/**
+ * add_wrap() - Intentionally perform a wrapping addition
+ * @a: first addend
+ * @b: second addend
+ *
+ * Return the potentially wrapped-around addition without
+ * tripping any overflow sanitizers that may be enabled.
+ */
+#define add_wrap(a, b) \
+ ({ \
+ typeof(a) __sum; \
+ if (check_add_overflow(a, b, &__sum)) \
+ /* do nothing */; \
+ __sum; \
+ })
+
/**
* check_sub_overflow() - Calculate subtraction with overflow checking
* @a: minuend; value to subtract from
--
2.34.1
