cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()

{
  "id": "8297a57bb8b81a3e66043fecb98915149bd83f418d4f147bff132ecff8dca0c8",
  "url": "https://osv.dev/vulnerability/CVE-2026-89641",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size() When the else branch of cifs_file_set_size() finds a writable file handle via find_writable_file(), it borrows tcon and server from the handle's tlink, attempts the handle-based set_file_size() RPC, and then releases the handle with cifsFileInfo_put(). If set_file_size() fails, execution falls through to the path-based fallback, which reuses the borrowed tcon and server under the \"if (tcon == NULL)\" guard. Since tcon is not NULL at that point, the guard is skipped. If cifsFileInfo_put() dropped the last reference on a tlink that was already removed from the tlink tree (TCON_LINK_IN_TREE cleared, as happens during reconnection or session teardown), cifs_put_tlink() will have freed tcon; the subsequent set_path_size() call is then a use-after-free. Setting tcon = NULL after cifsFileInfo_put() causes the existing guard to take the cifs_sb_tlink() path, which acquires a fresh reference for the path-based operation or fails cleanly if the session is gone.",
    "evidence": "osv:CVE-2026-89641",
    "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-2026-89641",
      "aliases": [
        "CVE-2026-89641"
      ],
      "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": "110fee6b9bb58a5c50047fc2594d415f741b591e"
                },
                {
                  "fixed": "4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4"
                },
                {
                  "fixed": "4bea15d9c7683218f57b8c1f5f0aa75cab76af8d"
                },
                {
                  "fixed": "b96db32fed8dfb2478d7c208f89bf383beed1535"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89641.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-2026-89641.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:22.627368627Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4bea15d9c7683218f57b8c1f5f0aa75cab76af8d",
        "https://git.kernel.org/stable/c/4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4",
        "https://git.kernel.org/stable/c/b96db32fed8dfb2478d7c208f89bf383beed1535",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89641.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89641",
        "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-2026-89641.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89641",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489208,
  "published_at": "2026-09-11T19:45:34.036+00:00"
}