CVE-2026-72358

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

drm/xe/pt: prevent invalid cursor access for purged BOs

During a page table walk for binding, xeptstagebind() explicitly skips initializing the xeres_cursor for purged BOs, treating them similarly to NULL VMAs by only setting the cursor size.

However, xepthugeptepossible() and xeptscan64K() did not check if the BO was purged before attempting to walk the cursor using xeresdma() and xeresnext(). Because the cursor was left uninitialized for purged BOs, this falls through and triggers warnings like:

WARNING: drivers/gpu/drm/xe/xerescursor.h:274 at xeresnext

Fix this by explicitly checking if the BO is purged in both xepthugeptepossible() and xeptscan64K(), returning early just as we do for NULL VMAs, avoiding the invalid cursor accesses entirely.

As a precaution, also zero-initialize the cursor in xeptstage_bind() to ensure we don't pass garbage data into the page table walkers if we ever hit a similar edge case in the future.

(cherry picked from commit 4c7b9c6ece32440e5a435a92076d049450cd2d2e)