ovl: fix double end_creating() on the casefold-mismatch path

{
  "id": "bbb2a788a2886eda2dd2ec322f5df0240cbd1c470948414fde09e044b4cea7e7",
  "url": "https://osv.dev/vulnerability/CVE-2026-89767",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ovl: fix double end_creating() on the casefold-mismatch path",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ovl: fix double end_creating() on the casefold-mismatch path ovl_create_real() releases the new dentry twice when the casefold consistency check fails. The S_IFDIR branch calls end_creating() and sets err, then falls through to the common out: label which calls end_creating() on the same dentry again: case S_IFDIR: newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode); err = PTR_ERR_OR_ZERO(newdentry); if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) { pr_warn_ratelimited(...); end_creating(newdentry); /* first */ err = -EINVAL; } break; ... if (err) goto out; ... out: if (err) { end_creating(newdentry); /* second, same dentry */ return ERR_PTR(err); } end_creating() is end_dirop(), which does inode_unlock() on the parent and dput() on the dentry, so the parent directory's i_rwsem is unlocked twice and the dentry is put twice. The second unlock releases a lock that is not held, which is what wedges every later creation under that parent, and the second dput() drops a reference that was never taken. The branch was added by commit dfc7da402ccc (\"ovl: Check for casefold consistency when creating new dentries\") as a bare dput(), which already released the reference twice; commit fe497f0759e0 (\"VFS: change vfs_mkdir() to unlock on failure.\") converted both sites to end_creating(), adding the double unlock. This is reachable by an unprivileged user. The casefold consistency of the layers is valida",
    "evidence": "osv:CVE-2026-89767",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.51",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-89767",
      "aliases": [
        "CVE-2026-89767"
      ],
      "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": "dfc7da402ccc92d6e4b01a4778a3f15f2496b9af"
                },
                {
                  "fixed": "2fa220bc0f84597cb6de665e5b5021c5901ddf00"
                },
                {
                  "fixed": "b1aa8ab78a8e87aee9e306971465408e059f839a"
                },
                {
                  "fixed": "077ab8985ee278c3d8618182d335b0f0cd919e16"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89767.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.18.0"
                },
                {
                  "fixed": "6.18.51"
                }
              ]
            },
            {
              "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-2026-89767.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:42.905364635Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/077ab8985ee278c3d8618182d335b0f0cd919e16",
        "https://git.kernel.org/stable/c/2fa220bc0f84597cb6de665e5b5021c5901ddf00",
        "https://git.kernel.org/stable/c/b1aa8ab78a8e87aee9e306971465408e059f839a",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89767.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89767",
        "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-2026-89767.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89767",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 510970,
  "published_at": "2026-09-11T19:47:07.353+00:00"
}