linux-kernel - Re: [PATCH] ubsan: integer-overflow: depend on BROKEN to keep this out of CI

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Message-ID: <202505281559.FD37A978F@keescook>
Date: Wed, 28 May 2025 16:00:03 -0700
From: Kees Cook <kees@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Justin Stitt <justinstitt@...gle.com>,
	Eric Biggers <ebiggers@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Jann Horn <jannh@...gle.com>, Marco Elver <elver@...gle.com>,
	llvm@...ts.linux.dev, linux-hardening@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ubsan: integer-overflow: depend on BROKEN to keep this
 out of CI

On Wed, May 28, 2025 at 02:32:23PM -0700, Nathan Chancellor wrote:
> On Wed, May 28, 2025 at 11:26:22AM -0700, Kees Cook wrote:
> > Depending on !COMPILE_TEST isn't sufficient to keep this feature out of
> > CI because we can't stop it from being included in randconfig builds.
> > This feature is still highly experimental, and is developed in lock-step
> > with Clang's Overflow Behavior Types[1]. Depend on BROKEN to keep it
> > from being enabled by anyone not expecting it.
> > 
> > Link: https://discourse.llvm.org/t/rfc-v2-clang-introduce-overflowbehaviortypes-for-wrapping-and-non-wrapping-arithmetic/86507 [1]
> > Signed-off-by: Kees Cook <kees@...nel.org>
> 
> Should this have a 'Cc: stable@...r.kernel.org' on it? There might not
> be much randconfig testing on stable but it is still very much possible
> for some random user to turn this on and report problems.

Ah yeah, I should probably do this via a proper Fixes: tag. I'll add
this.

> Regardless of that though, I think this is a good idea with how much of
> this feature is still being ironed out.
> 
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>

Thanks!

> 
> Once this lands, I plan to mark all issues in the CBL issue tracker that
> came about from UBSAN_INTEGER_WRAP as 'have a workaround applied' since
> it will not be possible for regular users to hit them but you may
> consider notating them in case they need to be addressed before the
> feature can be reenabled.

Sounds good!

-Kees

-- 
Kees Cook