Re: [RFC] Randomness on confidential computing platforms

[Kirill A. Shutemov]

On Mon, Jan 29, 2024 at 08:30:11AM -0800, Dave Hansen wrote:
> On 1/26/24 05:42, Kirill A. Shutemov wrote:
> > 3. Panic after enough re-tries of RDRAND/RDSEED instructions fail.
> >    Another DoS variant against the Guest.
> 
> I think Sean was going down the same path, but I really dislike the idea
> of having TDX-specific (or CoCo-specific) policy here.
> 
> How about we WARN_ON() RDRAND/RDSEED going bonkers?  The paranoid folks
> can turn on panic_on_warn, if they haven't already.

Sure, we can do it for kernel, but we have no control on what userspace
does.

Sensible userspace on RDRAND/RDSEED failure should fallback to kernel
asking for random bytes, but who knows if it happens in practice
everywhere.

Do we care?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov