Re: [PATCH] hwrng: virtio: reject invalid used.len from the device

[Michael Bommarito]

On Fri, Apr 17, 2026 at 8:31 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> Actionable meaning what?

Well, between the BLAKE2 pass and the fact that 99% of guests already
shouldn't trust what's above, I agree that actionable doesn't mean
much to most people, not even for breaking KASLR.

But after doing some research, I realized that SEV-SNP/TDX guests that
expect lockdown=confidentiality might actually expect otherwise under
that security model.  Still not a lot to work with, but more than just
correctness in those cases, and those might be the environments that
care the most.

> Maybe clamp at sizeof(vi->data) then? 0 might break buggy devices that
> were working earlier.
> Or just clamp where it's used, for clarity.
> And maybe we need the array_index dance, given
> you are worried about malicious.

Happy to send a v2 with those changes but I can only test on a 1-2 TDX
variants at home and don't have access to an EPYC bare metal box, so
not very confident about your buggy device point