linux-kernel - [PATCH v2 0/5] overflow: Introduce wrapping helpers

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Message-Id: <20240130220218.it.154-kees@kernel.org>
Date: Tue, 30 Jan 2024 14:06:05 -0800
From: Kees Cook <keescook@...omium.org>
To: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Cc: Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Marco Elver <elver@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Masahiro Yamada <masahiroy@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH v2 0/5] overflow: Introduce wrapping helpers

Hi,

v2:
 - Define inc/dec_wrap() in terms of add/sub_wrap() and avoid side-effects (Rasmus)
 - Fix various typos (Rasmus)
 - Add selftests for all the new helpers
v1: https://lore.kernel.org/lkml/20240129182845.work.694-kees@kernel.org/

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 *_wrap()
helpers first argument being the output type makes the most sense (as
suggested by Rasmus).

-Kees

Link: https://github.com/KSPP/linux/issues/26 [1]
Link: https://github.com/KSPP/linux/issues/27 [2]
Link: https://github.com/KSPP/linux/issues/344 [3]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=devel/overflow/enable-unsigned-sanitizer [4]

Kees Cook (5):
  overflow: Adjust check_*_overflow() kern-doc to reflect results
  overflow: Expand check_add_overflow() for pointer addition
  overflow: Introduce add_would_overflow()
  overflow: Introduce add_wrap(), sub_wrap(), and mul_wrap()
  overflow: Introduce inc_wrap() and dec_wrap()

 include/linux/compiler_types.h |  10 +++
 include/linux/overflow.h       | 160 ++++++++++++++++++++++++++++++---
 lib/overflow_kunit.c           | 132 ++++++++++++++++++++++++---
 3 files changed, 277 insertions(+), 25 deletions(-)

-- 
2.34.1