Re: [PATCH] x86/fpu: verify xstate buffer size according with requested features

[Thomas Gleixner]

On Thu, Jan 18 2024 at 10:27, Dave Hansen wrote:
> If we have nice, reliable fault handling and then decide that we've got
> XRSTOR's running amok reading random memory all over the place that need
> a nicer error message, then we can add that code to predict the future.
> If our "predict the future" code goes wrong, then we lose an error
> message -- not a big deal.

After staring more at it, it's arguable to pass fpstate->user_size to
fault_in_readable() and ignore fx_sw->xstate_size completely.

That's a guaranteed to be reliable size which prevents endless loops
because arguably that's the maximum size which can be touched by XRSTOR,
no?

Thanks,

        tglx