linux-hardening - [PATCH v3 0/3] overflow: Introduce wrapping helpers

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Date: Mon,  5 Feb 2024 01:12:28 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-hardening@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
	Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Marco Elver <elver@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/3] overflow: Introduce wrapping helpers

Hi,

v3:
 - reduce patches to just docs and new helpers; we don't need pointer fixes yet.
v2: https://lore.kernel.org/all/20240130220218.it.154-kees@kernel.org/
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 (3):
  overflow: Adjust check_*_overflow() kern-doc to reflect results
  overflow: Introduce add_wrap(), sub_wrap(), and mul_wrap()
  overflow: Introduce inc_wrap() and dec_wrap()

 include/linux/overflow.h | 100 ++++++++++++++++++++++++++++++++++-----
 lib/overflow_kunit.c     |  65 +++++++++++++++++++++++--
 2 files changed, 149 insertions(+), 16 deletions(-)

-- 
2.34.1