CVE-2026-46216

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

drm/xe/hdcp: Add NULL check for media_gt in intel_hdcp_gsc_check_status()

When media GT is disabled via configfs, there is no allocation for
media_gt, which is kept as NULL.  In such scenario,
intel_hdcp_gsc_check_status() results in a kernel pagefault error due to
&gt->uc.gsc being evaluated as an invalid memory address.

Fix that by introducing a NULL check on media_gt and bailing out early
if so.

While at it, also drop the NULL check for gsc, since it can't be NULL if
media_gt is not NULL.

v2:
  - Get address for gsc only after checking that gt is not NULL.
    (Shuicheng)
  - Drop the NULL check for gsc. (Shuicheng)
v3:
  - Add "Fixes" and "Cc: <stable...>" tags. (Matt)

(cherry picked from commit bfaf87e84ca3ca3f6e275f9ae56da47a8b55ffd1)