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

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  "url": "https://osv.dev/vulnerability/CVE-2026-74449",
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  "payload": {
    "kind": "advisory",
    "title": "drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport If a plane reaches calculate_mcache_setting with a zero-area viewport, calculate_mcache_setting exits early with num_mcaches == 0 and mvmpg_width/height == 0. This will cause a divide-by-zero panic and can also cause an underflow on num_mcaches. Fix this by changing calculate_mcache_setting to bool and adding guards after each calculate_mcache_row_bytes call. If num_mcaches 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)",
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      "modified": "2026-10-28T02:30:29.150921727Z",
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      "references": [
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  "source_id": "core-osv",
  "document_id": 495948,
  "published_at": "2026-08-15T12:26:54.519+00:00"
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