{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "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:  \tcase S_IFDIR: \t\tnewdentry = ovl_do_mkdir(ofs, dir, newdentry, attr-\u003emode); \t\terr = PTR_ERR_OR_ZERO(newdentry); \t\tif (!err \u0026\u0026 ofs-\u003ecasefold != ovl_dentry_casefolded(newdentry)) { \t\t\tpr_warn_ratelimited(...); \t\t\tend_creating(newdentry);\t/* first */ \t\t\terr = -EINVAL; \t\t} \t\tbreak; \t... \tif (err) \t\tgoto out; \t...  out: \tif (err) { \t\tend_creating(newdentry);\t/* second, same dentry */ \t\treturn ERR_PTR(err); \t}  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 validated at mount time in ovl_parse_layer(), and again on every lookup in ovl_lookup_single(), but ofs-\u003eworkdir is the internal \"work\" subdirectory created inside the user-supplied workdir, and that subdirectory is not re-checked.  Marking it casefolded after the mount therefore makes every ovl_create_temp() inherit the wrong state - and that path reaches ovl_create_real() through ovl_start_creating_temp(), which uses start_creating() with a generated name and so never runs the lookup-time check.    unshare -Urm   mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt   mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged   mount -t overlay ovl -o lowerdir=mnt/lower,\\         upperdir=mnt/upper,workdir=mnt/work mnt/merged   chattr +F mnt/work/work   mkdir mnt/merged/d/sub\t\t# directory copy-up    overlayfs: wrong inherited casefold (work/#5)  and the next copy-up blocks forever on the parent's i_rwsem:    mkdir           D  start_creating+0x65/0xb0                      ovl_start_creating_temp+0xb0/0xe0 [overlay]                      ovl_create_temp+0xa3/0x1d0 [overlay]                      ovl_copy_up_one+0x1f1c/0x21c0 [overlay]                      ovl_copy_up_flags+0xf5/0x140 [overlay]                      ovl_create_object+0xb7/0x220 [overlay]                      ovl_mkdir+0x23/0x40 [overlay]  Drop the end_creating() from the branch and let out: own the cleanup, which is what every other error path in this function already does.",
  "id": "DEBIAN-CVE-2026-89767",
  "modified": "2026-09-14T08:47:42.727213098Z",
  "published": "2026-09-11T20:20:07.960Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-89767"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-89767"
  ]
}