Re: arc4random - are you sure we want these?

[Florian Weimer <fweimer@redhat.com>]

* Cristian Rodríguez:

> On Sat, Jul 23, 2022 at 12:25 PM Jason A. Donenfeld via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>
>> For that reason, past discussion of having some random number generation
>> in userspace libcs has geared toward doing this in the vDSO, somehow,
>> where the kernel can be part and parcel of that effort.
>
> On linux just making this interface call "something" from the VDSO that
>
> - does not block.
> - cannot ever fail or if it does indeed need to bail out it kills the
> calling thread as last resort.
>
> (if neither of those can be provided, we are back to square one)
>
> Will be beyond awesome because it could be usable everywhere,
> including the dynamic linker, malloc or whatever else
> question is..is there any at least experimental patch  with a hope of
> beign accepted available ?

I agree that this would be nice, but we'd like have to donate
thread-specific data for kernel use, and that's currently totally
vaporware.

The “cannot ever fail” part is impossible to achieve due to old kernels
and seccomp filters.  Low-level userspace needs to paper over it in some
way, so that applications don't have to deal with it.

Thanks,
Florian