Re: [PATCH 7/8] x86/fpu: Pre-fault only required size of xstate buffer

[Chang S. Bae]

On 8/16/2026 9:20 PM, Andrei Vagin wrote:
> The kernel previously used the default task FPU state size (user_size)
> to fault in the user buffer when restoring FPU registers from a signal
> frame. This can lead to attempting to fault in memory past the end of
> the actual frame if the frame was smaller than the default size.
>
> Introduce consistency checks to calculate the actual required size for
> the features enabled in the xfeatures mask, ensure that the provided
> xstate_size is sufficient, and shrink it to the actual required size.
> Use this validated size to fault in the user buffer.
>
> Keep the strict check that the provided xstate_size does not exceed the
> default user_size for now.
I think this consistency check should have been there already. Thanks!

  Reviewed-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>

Thanks,
Chang