Re: [PATCH 3/5] compiler_attributes: Add overflow_behavior macros __ob_trap and __ob_wrap

Linus Torvalds
2026-03-31T17:24:19Z

On Tue, 31 Mar 2026 at 09:37, Kees Cook <kees@kernel.org> wrote:
>> +
> + typedef unsigned int __attribute__((overflow_behavior(trap))) safe_uint;
> + typedef unsigned int __attribute__((overflow_behavior(wrap))) wrapping_uint;

This is fundamentally broken sh*t.

Stop thinking that trapping is "safe".

It damn well isn't. A dead machine is not a safe machine.

Any patches that call trapping behavior safe will ne NAK'ed by me.,

We have decades of peoiple using BUG_ON() as a safety measure, and it
has been a HUGE PROBLEM.

There is no way in hell that we are ever adding implicit BUG_ON()
things that are this hidden, this easy to use, and then mislabeled as
being "safe".

Guys, that's the same logic as having a airbag in your car that just
shoots you in the head. You're certainly "safe" from the vagaries of
bad healthcare. But dammit, if anybody thinks that a "bullet to the
head" should be called "safe", then that person damn well shouldn't be
involved with kernel development.

So NAK NAK NAK NAK.

The only safe trapping behavior is something that has a clear an
unambiguous and simple to use way to *HANDLE* it. Not just "mark it
trapping".

Linus