platform/x86: panasonic-laptop: Fix sentinel write past pcc->sinf[]

{
  "id": "2611c410dc3397f12d92572ff56094d836575c387703ada1b49e7109c470120f",
  "url": "https://osv.dev/vulnerability/CVE-2026-89436",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "platform/x86: panasonic-laptop: Fix sentinel write past pcc->sinf[]",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: platform/x86: panasonic-laptop: Fix sentinel write past pcc->sinf[] acpi_pcc_retrieve_biosdata() rejects SINF packages only when pcc->num_sifr is strictly less than hkey->package.count, then unconditionally writes a trailing sentinel at pcc->sinf[hkey->package.count]. But pcc->sinf[] is allocated with exactly pcc->num_sifr elements (valid indices 0..num_sifr-1), so that write needs num_sifr strictly greater than package.count to stay in bounds -- num_sifr == package.count passes the existing check but still overflows by one element. This is exactly the case probe()'s existing num_sifr++ workaround (\"Some DSDT-s have an off-by-one bug where the SINF package count is one higher than the SQTY reported value\") is written to accommodate: when a DSDT's SINF package count equals SQTY+1, the workaround makes num_sifr equal to package.count, which is precisely the boundary that overflows here. Found via UBSan (array-index-out-of-bounds) on hardware where HKEY.SQTY returns 37 and HKEY.SINF()'s package has 38 elements: num_sifr becomes 38 after the += 1 workaround, the loop correctly fills indices 0..37, and the sentinel write then targets index 38, one past the end -- a silent 4-byte heap overflow on kernels without CONFIG_UBSAN. Tightening the rejection check to num_sifr <= package.count would avoid the overflow but breaks probe() entirely on exactly this hardware, since num_sifr == package.count is the case the off-b",
    "evidence": "osv:CVE-2026-89436",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-89436",
      "aliases": [
        "CVE-2026-89436"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "a3d0dbd18ce908292607bb6cf37c978ece8a33d4"
                },
                {
                  "fixed": "a93df956ee4d903735b6d395362c839cb1dc07e3"
                },
                {
                  "fixed": "329f10d8be193bf36af124e00b9dd6644cd71724"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89436.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.2.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89436.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.110221668Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/329f10d8be193bf36af124e00b9dd6644cd71724",
        "https://git.kernel.org/stable/c/a93df956ee4d903735b6d395362c839cb1dc07e3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89436.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89436",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89436.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89436",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 509080,
  "published_at": "2026-09-11T19:43:06.732+00:00"
}