linux-hardening - [PATCH v5 0/3] overflow: Introduce wrapping helpers

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Date: Wed,  7 Feb 2024 07:24:17 -0800
From: Kees Cook <keescook@...omium.org>
To: Andy Shevchenko <andy@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Marco Elver <elver@...gle.com>,
	Eric Biggers <ebiggers@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v5 0/3] overflow: Introduce wrapping helpers

v5: drop redundant checks (gustavo)
v4: https://lore.kernel.org/linux-hardening/20240206102354.make.081-kees@kernel.org/
v3: https://lore.kernel.org/all/20240205090854.make.507-kees@kernel.org/
v2: https://lore.kernel.org/all/20240130220218.it.154-kees@kernel.org/
v1: https://lore.kernel.org/lkml/20240129182845.work.694-kees@kernel.org/

Hi,

In preparation for gaining instrumentation for signed[1], unsigned[2], and
pointer[3] wrap-around, expand the overflow header to include wrap-around
helpers that can be used to annotate arithmetic where wrapped calculations
are expected (e.g. atomics).

After spending time getting the unsigned integer wrap-around sanitizer
running warning-free on a basic x86_64 boot[4], I think the add/sub/mul
helpers first argument being the output type makes the most sense (as
suggested by Rasmus).

-Kees


Kees Cook (3):
  overflow: Adjust check_*_overflow() kern-doc to reflect results
  overflow: Introduce wrapping_add(), wrapping_sub(), and wrapping_mul()
  overflow: Introduce wrapping_inc() and wrapping_dec()

 include/linux/overflow.h | 98 +++++++++++++++++++++++++++++++++++-----
 lib/overflow_kunit.c     | 67 +++++++++++++++++++++++++--
 2 files changed, 149 insertions(+), 16 deletions(-)

-- 
2.34.1