[v2,0/5] overflow: Introduce wrapping helpers

Message

Kees Cook Jan. 30, 2024, 10:06 p.m. UTC

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/[e-mail]/

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(-)