[PATCH 6.6.y 0/2] fbdev: backport CVE-2025-21976

Hi Greg, Sasha, and maintainers,

I'm working through the smaller CVE backports still missing from 6.6.y.
These 2 upstream changes belong together for CVE-2025-21976. They must be
applied in this order because the later change depends on or completes the
earlier one.

The complete series is already present in 6.12.y, 6.18.y, and 7.2.y.
These fixes also affect 6.1.y, which will need a separate backport; this
series is only for 6.6.y.

Could you please consider this series for 6.6.y?

Thanks,
Artem Dinaburg

Series:
  1. fbdev: hyperv_fb: Simplify hvfb_putmem
  2. fbdev: hyperv_fb: Allow graceful removal of framebuffer

base: v6.6.157 (79643295eba17affbd16ca97f3ef04c90266b28c) plus stable-queue
revision 958ddf240a33ef26b1771be944f0ea6c3b597472