Re: alloca

[Jeffrey Walton]

On Sun, Jul 26, 2020 at 9:34 AM Bruno Haible <bruno@clisp.org> wrote:
>
> Hi Jeffrey,
>
> > All alloca() code should be removed; not just CRAY.
> > alloca() is a dangerous compiler builtin.
>
> I disagree: when you use it with bounded allocation size only (e.g. through
> the module 'malloca'), there is no danger.

Intel has banned the function:
https://github.com/intel/safestringlib/wiki/SDL-List-of-Banned-Functions

Microsoft has banned the function:
https://docs.microsoft.com/en-us/previous-versions/bb288454(v=msdn.10)?redirectedfrom=MSDN

Apple has banned the function:
https://developer.apple.com/library/archive/documentation/Security/Conceptual/SecureCodingGuide/Introduction.html

The manufacturer tells you not to use it on their platforms

> > It does not convey failure
>
> A plain function entry does not convey failure either.

?

> Note that the module 'scratch_buffer' is overkill for these cases:
> if you can determine the allocation size ahead, and it is less than 1 KB,
> why should the code waste 1 KB of stack space?

It is not about size.

It is about reducing attack surface and risk.

It is a Certification & Accreditation (C&A) item. It's about passing an audit.

Jeff