CVE-2025-40105 (GCVE-0-2025-40105)

Vulnerability from cvelistv5 – Published: 2025-10-30 09:48 – Updated: 2025-12-01 06:18
VLAI?
Summary
In the Linux kernel, the following vulnerability has been resolved: vfs: Don't leak disconnected dentries on umount When user calls open_by_handle_at() on some inode that is not cached, we will create disconnected dentry for it. If such dentry is a directory, exportfs_decode_fh_raw() will then try to connect this dentry to the dentry tree through reconnect_path(). It may happen for various reasons (such as corrupted fs or race with rename) that the call to lookup_one_unlocked() in reconnect_one() will fail to find the dentry we are trying to reconnect and instead create a new dentry under the parent. Now this dentry will not be marked as disconnected although the parent still may well be disconnected (at least in case this inconsistency happened because the fs is corrupted and .. doesn't point to the real parent directory). This creates inconsistency in disconnected flags but AFAICS it was mostly harmless. At least until commit f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") which removed adding of most disconnected dentries to sb->s_anon list. Thus after this commit cleanup of disconnected dentries implicitely relies on the fact that dput() will immediately reclaim such dentries. However when some leaf dentry isn't marked as disconnected, as in the scenario described above, the reclaim doesn't happen and the dentries are "leaked". Memory reclaim can eventually reclaim them but otherwise they stay in memory and if umount comes first, we hit infamous "Busy inodes after unmount" bug. Make sure all dentries created under a disconnected parent are marked as disconnected as well.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < b5abafd0aa8d7bcb935c8f91e4cfc2f2820759e4 (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < 20863bb7fbb016379f8227122edfabc5c799bc79 (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < 8004d4b8cbf1bd68a23c160d57287e177c82cc69 (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < 7e0c8aaf4e28918abded547a5147c7d52c4af7d2 (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < cebfbf40056a4d858b2a3ca59a69936d599bd209 (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < 620f3b0ede9c5cb4976cd0457d0b04ad551e5d6b (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < eadc49999fa994d6fbd70c332bd5d5051cc42261 (git)
Affected: f1ee616214cb22410e939d963bbb2349c2570f02 , < 56094ad3eaa21e6621396cc33811d8f72847a834 (git)
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    Linux Linux Affected: 4.16
Unaffected: 0 , < 4.16 (semver)
Unaffected: 5.4.301 , ≤ 5.4.* (semver)
Unaffected: 5.10.246 , ≤ 5.10.* (semver)
Unaffected: 5.15.196 , ≤ 5.15.* (semver)
Unaffected: 6.1.158 , ≤ 6.1.* (semver)
Unaffected: 6.6.114 , ≤ 6.6.* (semver)
Unaffected: 6.12.55 , ≤ 6.12.* (semver)
Unaffected: 6.17.5 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "fs/dcache.c"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvfs: Don\u0027t leak disconnected dentries on umount\n\nWhen user calls open_by_handle_at() on some inode that is not cached, we\nwill create disconnected dentry for it. If such dentry is a directory,\nexportfs_decode_fh_raw() will then try to connect this dentry to the\ndentry tree through reconnect_path(). It may happen for various reasons\n(such as corrupted fs or race with rename) that the call to\nlookup_one_unlocked() in reconnect_one() will fail to find the dentry we\nare trying to reconnect and instead create a new dentry under the\nparent. Now this dentry will not be marked as disconnected although the\nparent still may well be disconnected (at least in case this\ninconsistency happened because the fs is corrupted and .. doesn\u0027t point\nto the real parent directory). This creates inconsistency in\ndisconnected flags but AFAICS it was mostly harmless. At least until\ncommit f1ee616214cb (\"VFS: don\u0027t keep disconnected dentries on d_anon\")\nwhich removed adding of most disconnected dentries to sb-\u003es_anon list.\nThus after this commit cleanup of disconnected dentries implicitely\nrelies on the fact that dput() will immediately reclaim such dentries.\nHowever when some leaf dentry isn\u0027t marked as disconnected, as in the\nscenario described above, the reclaim doesn\u0027t happen and the dentries\nare \"leaked\". Memory reclaim can eventually reclaim them but otherwise\nthey stay in memory and if umount comes first, we hit infamous \"Busy\ninodes after unmount\" bug. Make sure all dentries created under a\ndisconnected parent are marked as disconnected as well."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-01T06:18:08.529Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        {
          "url": "https://git.kernel.org/stable/c/56094ad3eaa21e6621396cc33811d8f72847a834"
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      "title": "vfs: Don\u0027t leak disconnected dentries on umount",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40105",
    "datePublished": "2025-10-30T09:48:09.674Z",
    "dateReserved": "2025-04-16T07:20:57.165Z",
    "dateUpdated": "2025-12-01T06:18:08.529Z",
    "state": "PUBLISHED"
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  }
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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