CVE-2026-74449

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Fix divide-by-zero in calculatemcachesetting on zero viewport

If a plane reaches calculatemcachesetting with a zero-area viewport, calculatemcachesetting exits early with nummcaches == 0 and mvmpgwidth/height == 0. This will cause a divide-by-zero panic and can also cause an underflow on num_mcaches.

Fix this by changing calculatemcachesetting to bool and adding guards after each calculatemcacherowbytes call. If nummcaches or mvmpg_width/height is zero, return a false. Callers will propagate the failure as a rejected mode, which prevents the panic.

(cherry picked from commit 29c0f7c655f47bcbd575ff75e58480df6ec3c9da)