FKIE_CVE-2026-98990

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: check a submount for references right before unmounting it shrink_submounts() and mark_mounts_for_expiry() first collect all the mounts they are allowed to unmount and then unmount them. Whether a mount is busy is decided by propagate_mount_busy() on the tree. But unmounting the first mount changes the tree that the second one propagates into. propagate_umount() moves a surviving overmount off a copy it unmounts and mounts it where the copy was mounted. If that's where the propagated copy of the second victim is looked up the overmount becomes a candidate of the second umount_tree(). It's childless and so trim_one() commits it without looking at its reference count. So a synchronous umount pulls out a busy mount that is in use somewhere else and marks it MNT_SYNC_UMOUNT while it has users: umount2(/tmp/plshrink/p1, 0) = 0 errno 0 cwd is (unreachable) The same two umounts requested one after the other fail with EBUSY. This needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of NFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts inherit the flag. Check each mount right before it is unmounted under the same hold of namespace_sem and mount_lock as the umount itself. Make sure that the algorithm stays linear.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/18902a23ef36f83d32bafc58ae2484e6bb4bb8ef
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/32bf92416614a1e3ff3524fc6b780259c7aad3ef
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6e4012e571867868b545c91ca9d6095fdb709907
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d73f04e92c1aab78d96ac6cadb234c8a3a373d22
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f6394281834492c6516a405a348b545ae698a331
Impacted products
Vendor Product Version
To clipboard 

{
  "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": "f6394281834492c6516a405a348b545ae698a331",
              "status": "affected",
              "version": "1064f874abc0d05eeed8993815f584d847b72486",
              "versionType": "git"
            },
            {
              "lessThan": "6e4012e571867868b545c91ca9d6095fdb709907",
              "status": "affected",
              "version": "1064f874abc0d05eeed8993815f584d847b72486",
              "versionType": "git"
            },
            {
              "lessThan": "d73f04e92c1aab78d96ac6cadb234c8a3a373d22",
              "status": "affected",
              "version": "1064f874abc0d05eeed8993815f584d847b72486",
              "versionType": "git"
            },
            {
              "lessThan": "18902a23ef36f83d32bafc58ae2484e6bb4bb8ef",
              "status": "affected",
              "version": "1064f874abc0d05eeed8993815f584d847b72486",
              "versionType": "git"
            },
            {
              "lessThan": "32bf92416614a1e3ff3524fc6b780259c7aad3ef",
              "status": "affected",
              "version": "1064f874abc0d05eeed8993815f584d847b72486",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "5e6ef5ef6eaf690faad3a7c6c665ebf45d7b6ccf",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "839d42687dfce0ed0ea2c6bd8d707cc0e276fbe7",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "808e83e5add13152bd4a88346487de68395c136b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "6de9d08a9718ee9c12ba6343c50141c2d633e3dc",
              "versionType": "git"
            },
            {
              "lessThan": "4.2",
              "status": "affected",
              "version": "4.1.40",
              "versionType": "semver"
            },
            {
              "lessThan": "4.5",
              "status": "affected",
              "version": "4.4.54",
              "versionType": "semver"
            },
            {
              "lessThan": "4.10",
              "status": "affected",
              "version": "4.9.15",
              "versionType": "semver"
            },
            {
              "lessThan": "4.11",
              "status": "affected",
              "version": "4.10.3",
              "versionType": "semver"
            }
          ]
        },
        {
          "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": "4.11"
            },
            {
              "lessThan": "4.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.113",
              "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: check a submount for references right before unmounting it\n\nshrink_submounts() and mark_mounts_for_expiry() first collect all the\nmounts they are allowed to unmount and then unmount them.\n\nWhether a mount is busy is decided by propagate_mount_busy() on the\ntree. But unmounting the first mount changes the tree that the second\none propagates into. propagate_umount()\nmoves a surviving overmount off a copy it unmounts and mounts it where\nthe copy was mounted. If that\u0027s where the propagated copy of the second\nvictim is looked up the overmount becomes a candidate of the second\numount_tree(). It\u0027s childless and so trim_one() commits it without\nlooking at its reference count.\n\nSo a synchronous umount pulls out a busy mount that is in use somewhere\nelse and marks it MNT_SYNC_UMOUNT while it has users:\n\n  umount2(/tmp/plshrink/p1, 0) = 0 errno 0\n  cwd is (unreachable)\n\nThe same two umounts requested one after the other fail with EBUSY.\nThis needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of\nNFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts\ninherit the flag.\n\nCheck each mount right before it is unmounted under the same hold of\nnamespace_sem and mount_lock as the umount itself. Make sure that the\nalgorithm stays linear."
    }
  ],
  "id": "CVE-2026-98990",
  "lastModified": "2026-10-23T13:17:20.980",
  "metrics": {},
  "published": "2026-10-23T13:17:20.980",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/18902a23ef36f83d32bafc58ae2484e6bb4bb8ef"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/32bf92416614a1e3ff3524fc6b780259c7aad3ef"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6e4012e571867868b545c91ca9d6095fdb709907"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d73f04e92c1aab78d96ac6cadb234c8a3a373d22"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f6394281834492c6516a405a348b545ae698a331"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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