FKIE_CVE-2026-98978

Vulnerability from fkie_nvd - Published: 2026-10-23 13:17 - Updated: 2026-10-23 13:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: namespace: never expire a locked mount Locked mounts are special. They protect the underlying files and directories from being revealed. do_umount() refuses to unmount locked mounts but shrink_submounts() doesn't. A shrinkable mount can become locked once the owner of a user namespace puts it beneath a locked mount with MOVE_MOUNT_BENEATH. The locked property now moves to the mount at the bottom making it possible to unmount the top mount. So umount() of an unlocked ancestor now expires the bottom mount first and the covered directory is revealed: move_mount(c -> x/hidden, MOVE_MOUNT_BENEATH) = 0 the cover after the lock moved: umount2(x/hidden) = 0 the holder of the lock: umount2(x/hidden) = EINVAL the root of the copy, busy: umount2(x) = EBUSY reads x/hidden/secret: "covered-by-root" So leave a locked mount alone as it dies together with its parent. A plain umount() of an unlocked mount with a locked one below it is EBUSY from now on. It's the same for any other locked child. A lazy umount still takes the whole tree. mark_mounts_for_expiry() never sees a locked mount. lock_mnt_tree() leaves a mount on an expiry list alone and nothing else puts a locked one on such a list. Add an assert for this.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6b8dc3713a76346d212abab46cbfc8d7070f534c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d23265a12e4991ce7aedce670c0b6b598cadb644
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f78ddcc872248c7aa1d7e904928441a0be4c6d5d
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/namespace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6b8dc3713a76346d212abab46cbfc8d7070f534c",
              "status": "affected",
              "version": "5ff9d8a65ce80efb509ce4e8051394e9ed2cd942",
              "versionType": "git"
            },
            {
              "lessThan": "d23265a12e4991ce7aedce670c0b6b598cadb644",
              "status": "affected",
              "version": "5ff9d8a65ce80efb509ce4e8051394e9ed2cd942",
              "versionType": "git"
            },
            {
              "lessThan": "f78ddcc872248c7aa1d7e904928441a0be4c6d5d",
              "status": "affected",
              "version": "5ff9d8a65ce80efb509ce4e8051394e9ed2cd942",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/namespace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.12"
            },
            {
              "lessThan": "3.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.57",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: never expire a locked mount\n\nLocked mounts are special. They protect the underlying files and\ndirectories from being revealed. do_umount() refuses to unmount locked\nmounts but shrink_submounts() doesn\u0027t.\n\nA shrinkable mount can become locked once the owner of a user namespace\nputs it beneath a locked mount with MOVE_MOUNT_BENEATH. The locked\nproperty now moves to the mount at the bottom making it possible to\nunmount the top mount.\n\nSo umount() of an unlocked ancestor now expires the bottom mount first\nand the covered directory is revealed:\n\n  move_mount(c -\u003e x/hidden, MOVE_MOUNT_BENEATH) = 0\n  the cover after the lock moved:  umount2(x/hidden) = 0\n  the holder of the lock:          umount2(x/hidden) = EINVAL\n  the root of the copy, busy:      umount2(x) = EBUSY\n  reads x/hidden/secret: \"covered-by-root\"\n\nSo leave a locked mount alone as it dies together with its parent. A\nplain umount() of an unlocked mount with a locked one below it is EBUSY\nfrom now on. It\u0027s the same for any other locked child. A lazy umount\nstill takes the whole tree.\n\nmark_mounts_for_expiry() never sees a locked mount. lock_mnt_tree()\nleaves a mount on an expiry list alone and nothing else puts a locked\none on such a list. Add an assert for this."
    }
  ],
  "id": "CVE-2026-98978",
  "lastModified": "2026-10-23T13:17:19.517",
  "metrics": {},
  "published": "2026-10-23T13:17:19.517",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6b8dc3713a76346d212abab46cbfc8d7070f534c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d23265a12e4991ce7aedce670c0b6b598cadb644"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f78ddcc872248c7aa1d7e904928441a0be4c6d5d"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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