drm/amdgpu/vcn4: Prevent OOB reads when parsing dec msg

These records connect through source-stated identifiers. Shared identifiers or dates alone do not establish shared exposure, root cause or applicability.

CVE-2026-46199 · Microsoft / collected KEV context

cve-program · CVE-2026-46199

• https://git.kernel.org/stable/c/88411caee8f576d6b5abf6531232fcc0ce756dc5
• https://git.kernel.org/stable/c/c72a8b4dc6d598e3831ef3abd9c6527dfbf4810e
• https://git.kernel.org/stable/c/7688143ca62edeecacb3ba0a2cea129dbd262a18
• https://git.kernel.org/stable/c/63b51e8a9d54317d31cc3856c1e12407070d5fc2
• https://git.kernel.org/stable/c/3c817a60b09eaab926e475088e750936efcc95ae
• https://git.kernel.org/stable/c/0a78f2bac1424deb7c9d5e09c6b8e849d8e8b648

No related operational record is retained in the current change model.