dm-pcache: validate kset key_num and intra-segment bounds

{
  "id": "aad7d607fc74106da6dfba39b009d40cd937aaf1cdd086aea1f814416dccf7b4",
  "url": "https://osv.dev/vulnerability/CVE-2026-80961",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "dm-pcache: validate kset key_num and intra-segment bounds",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: dm-pcache: validate kset key_num and intra-segment bounds Two more fields decoded from the cache device go unbounded. The kset key_num drives cache_kset_crc() and the replay loop in cache_replay(), the writeback worker and the GC worker, but only the magic and a fixed-seed CRC are checked first, so a non-last kset whose key_num exceeds the PCACHE_KSET_KEYS_MAX buffer reads past its end before the CRC compare. A key's intra-segment offset and length in cache_key_decode() are taken verbatim, so a key running past its segment is replayed into the cache tree and the data CRC check and every later read hit then copy adjacent persistent memory into the caller's bio -- an out-of-bounds read that leaks to user space. Both fields are controlled by whoever supplies the cache device (CAP_SYS_ADMIN); the CRC seed is public. Add kset_onmedia_valid() to bound key_num before any kset read, and reject a key whose offset plus length, computed in 64 bits, exceeds the segment data_size. Valid metadata is unaffected.",
    "evidence": "osv:CVE-2026-80961",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.50",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-80961",
      "aliases": [
        "CVE-2026-80961"
      ],
      "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": "1d57628ff95b32d5cfa8d8f50e07690c161e9cf0"
                },
                {
                  "fixed": "d8caf96040a06096276ab72f5e1e8547c014c564"
                },
                {
                  "fixed": "5ac38f4b4862fad6e7270fde5c3356a822ce74ca"
                },
                {
                  "fixed": "f11deb032fd84081e7831cffcba895d893054a22"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80961.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.18.0"
                },
                {
                  "fixed": "6.18.50"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80961.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:22.611361329Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/5ac38f4b4862fad6e7270fde5c3356a822ce74ca",
        "https://git.kernel.org/stable/c/d8caf96040a06096276ab72f5e1e8547c014c564",
        "https://git.kernel.org/stable/c/f11deb032fd84081e7831cffcba895d893054a22",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80961.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80961",
        "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/2026/80xxx/CVE-2026-80961.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80961",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489188,
  "published_at": "2026-09-11T19:42:27.847+00:00"
}