Re: [RFC] Randomness on confidential computing platforms

[H. Peter Anvin]

On January 29, 2024 2:18:50 PM PST, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>On 1/29/24 13:33, Kirill A. Shutemov wrote:
>>> Let's assume buggy userspace exists.  Is that userspace *uniquely*
>>> exposed to a naughty VMM or is that VMM just added to the list of things
>>> that can attack buggy userspace?
>> This is good question.
>> 
>> VMM has control over when a VCPU gets scheduled and on what CPU which
>> gives it tighter control over the target workload. It can make a
>> difference if there's small window for an attack before RDRAND is
>> functional again.
>
>This is all a bit too theoretical for my taste.  I'm fine with doing
>some generic mitigation (WARN_ON_ONCE(hardware_is_exhausted)), but we're
>talking about a theoretical attack with theoretical buggy software when
>in a theoretically unreachable hardware state.
>
>Until it's clearly much more practical, we have much bigger problems to
>worry about.

Again, do we even have a problem with the "hold the boot until we have entropy"option?