CVE-2026-68243

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

drm/i915/gem: Fix NULL deref in I915_CONTEXT_PARAM_SSEU

Setting context engine slot N into I915_ENGINE_CLASS_INVALID /
I915_ENGINE_CLASS_INVALID_NONE and attempting to apply
I915_CONTEXT_PARAM_SSEU to the same slot N will deref NULL.
Fix that.

Discovered using AI-assisted static analysis confirmed by
Intel Product Security.

(cherry picked from commit 36eda5b5c2d40da41cc0a5403c26986237cf9e87)