FKIE_CVE-2025-71069

Vulnerability from fkie_nvd - Published: 2026-01-13 16:16 - Updated: 2026-04-15 00:35
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: invalidate dentry cache on failed whiteout creation F2FS can mount filesystems with corrupted directory depth values that get runtime-clamped to MAX_DIR_HASH_DEPTH. When RENAME_WHITEOUT operations are performed on such directories, f2fs_rename performs directory modifications (updating target entry and deleting source entry) before attempting to add the whiteout entry via f2fs_add_link. If f2fs_add_link fails due to the corrupted directory structure, the function returns an error to VFS, but the partial directory modifications have already been committed to disk. VFS assumes the entire rename operation failed and does not update the dentry cache, leaving stale mappings. In the error path, VFS does not call d_move() to update the dentry cache. This results in new_dentry still pointing to the old inode (new_inode) which has already had its i_nlink decremented to zero. The stale cache causes subsequent operations to incorrectly reference the freed inode. This causes subsequent operations to use cached dentry information that no longer matches the on-disk state. When a second rename targets the same entry, VFS attempts to decrement i_nlink on the stale inode, which may already have i_nlink=0, triggering a WARNING in drop_nlink(). Example sequence: 1. First rename (RENAME_WHITEOUT): file2 → file1 - f2fs updates file1 entry on disk (points to inode 8) - f2fs deletes file2 entry on disk - f2fs_add_link(whiteout) fails (corrupted directory) - Returns error to VFS - VFS does not call d_move() due to error - VFS cache still has: file1 → inode 7 (stale!) - inode 7 has i_nlink=0 (already decremented) 2. Second rename: file3 → file1 - VFS uses stale cache: file1 → inode 7 - Tries to drop_nlink on inode 7 (i_nlink already 0) - WARNING in drop_nlink() Fix this by explicitly invalidating old_dentry and new_dentry when f2fs_add_link fails during whiteout creation. This forces VFS to refresh from disk on subsequent operations, ensuring cache consistency even when the rename partially succeeds. Reproducer: 1. Mount F2FS image with corrupted i_current_depth 2. renameat2(file2, file1, RENAME_WHITEOUT) 3. renameat2(file3, file1, 0) 4. System triggers WARNING in drop_nlink()
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0dde30753c1e8648665dbe069d814e540ce2fd37
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3d65e27e57aaa9d66709fda4cbfb62a87c04a3f5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3d95ed8cf980fdfa67a3ab9491357521ae576168
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/64587ab4d1f16fc94f70e04fa87b2e3f69f8a7bb
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7f2bae0c881aa1e0a6318756df692cc13df2cc83
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c89845fae250efdd59c1d4ec60e9e1c652cee4b6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d33f89b34aa313f50f9a512d58dd288999f246b0
Impacted products
Vendor Product Version
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: invalidate dentry cache on failed whiteout creation\n\nF2FS can mount filesystems with corrupted directory depth values that\nget runtime-clamped to MAX_DIR_HASH_DEPTH. When RENAME_WHITEOUT\noperations are performed on such directories, f2fs_rename performs\ndirectory modifications (updating target entry and deleting source\nentry) before attempting to add the whiteout entry via f2fs_add_link.\n\nIf f2fs_add_link fails due to the corrupted directory structure, the\nfunction returns an error to VFS, but the partial directory\nmodifications have already been committed to disk. VFS assumes the\nentire rename operation failed and does not update the dentry cache,\nleaving stale mappings.\n\nIn the error path, VFS does not call d_move() to update the dentry\ncache. This results in new_dentry still pointing to the old inode\n(new_inode) which has already had its i_nlink decremented to zero.\nThe stale cache causes subsequent operations to incorrectly reference\nthe freed inode.\n\nThis causes subsequent operations to use cached dentry information that\nno longer matches the on-disk state. When a second rename targets the\nsame entry, VFS attempts to decrement i_nlink on the stale inode, which\nmay already have i_nlink=0, triggering a WARNING in drop_nlink().\n\nExample sequence:\n1. First rename (RENAME_WHITEOUT): file2 \u2192 file1\n   - f2fs updates file1 entry on disk (points to inode 8)\n   - f2fs deletes file2 entry on disk\n   - f2fs_add_link(whiteout) fails (corrupted directory)\n   - Returns error to VFS\n   - VFS does not call d_move() due to error\n   - VFS cache still has: file1 \u2192 inode 7 (stale!)\n   - inode 7 has i_nlink=0 (already decremented)\n\n2. Second rename: file3 \u2192 file1\n   - VFS uses stale cache: file1 \u2192 inode 7\n   - Tries to drop_nlink on inode 7 (i_nlink already 0)\n   - WARNING in drop_nlink()\n\nFix this by explicitly invalidating old_dentry and new_dentry when\nf2fs_add_link fails during whiteout creation. This forces VFS to\nrefresh from disk on subsequent operations, ensuring cache consistency\neven when the rename partially succeeds.\n\nReproducer:\n1. Mount F2FS image with corrupted i_current_depth\n2. renameat2(file2, file1, RENAME_WHITEOUT)\n3. renameat2(file3, file1, 0)\n4. System triggers WARNING in drop_nlink()"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nf2fs: invalidar la cach\u00e9 de dentry en la creaci\u00f3n fallida de whiteout\n\nF2FS puede montar sistemas de archivos con valores de profundidad de directorio corruptos que se ajustan en tiempo de ejecuci\u00f3n a MAX_DIR_HASH_DEPTH. Cuando se realizan operaciones RENAME_WHITEOUT en dichos directorios, f2fs_rename realiza modificaciones de directorio (actualizando la entrada de destino y eliminando la entrada de origen) antes de intentar a\u00f1adir la entrada de whiteout a trav\u00e9s de f2fs_add_link.\n\nSi f2fs_add_link falla debido a la estructura de directorio corrupta, la funci\u00f3n devuelve un error a VFS, pero las modificaciones parciales del directorio ya se han confirmado en el disco. VFS asume que toda la operaci\u00f3n de renombrado fall\u00f3 y no actualiza la cach\u00e9 de dentry, dejando mapeos obsoletos.\n\nEn la ruta de error, VFS no llama a d_move() para actualizar la cach\u00e9 de dentry. Esto resulta en que new_dentry sigue apuntando al antiguo inodo (new_inode) al que ya se le ha decrementado su i_nlink a cero. La cach\u00e9 obsoleta causa que las operaciones subsiguientes referencien incorrectamente el inodo liberado.\n\nEsto hace que las operaciones subsiguientes utilicen informaci\u00f3n de dentry en cach\u00e9 que ya no coincide con el estado en disco. Cuando un segundo renombrado apunta a la misma entrada, VFS intenta decrementar i_nlink en el inodo obsoleto, que ya puede tener i_nlink=0, lo que activa una ADVERTENCIA en drop_nlink().\n\nSecuencia de ejemplo:\n1. Primer renombrado (RENAME_WHITEOUT): file2 ? file1\n   - f2fs actualiza la entrada file1 en disco (apunta al inodo 8)\n   - f2fs elimina la entrada file2 en disco\n   - f2fs_add_link(whiteout) falla (directorio corrupto)\n   - Devuelve error a VFS\n   - VFS no llama a d_move() debido al error\n   - La cach\u00e9 de VFS todav\u00eda tiene: file1 ? inodo 7 (\u00a1obsoleto!)\n   - el inodo 7 tiene i_nlink=0 (ya decrementado)\n\n2. Segundo renombrado: file3 ? file1\n   - VFS usa cach\u00e9 obsoleta: file1 ? inodo 7\n   - Intenta drop_nlink en el inodo 7 (i_nlink ya es 0)\n   - ADVERTENCIA en drop_nlink()\n\nSolucione esto invalidando expl\u00edcitamente old_dentry y new_dentry cuando f2fs_add_link falla durante la creaci\u00f3n de whiteout. Esto fuerza a VFS a actualizarse desde el disco en operaciones subsiguientes, asegurando la consistencia de la cach\u00e9 incluso cuando el renombrado tiene \u00e9xito parcialmente.\n\nReproductor:\n1. Monte la imagen F2FS con i_current_depth corrupto\n2. renameat2(file2, file1, RENAME_WHITEOUT)\n3. renameat2(file3, file1, 0)\n4. El sistema activa una ADVERTENCIA en drop_nlink()"
    }
  ],
  "id": "CVE-2025-71069",
  "lastModified": "2026-04-15T00:35:42.020",
  "metrics": {},
  "published": "2026-01-13T16:16:06.300",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0dde30753c1e8648665dbe069d814e540ce2fd37"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3d65e27e57aaa9d66709fda4cbfb62a87c04a3f5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3d95ed8cf980fdfa67a3ab9491357521ae576168"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/64587ab4d1f16fc94f70e04fa87b2e3f69f8a7bb"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7f2bae0c881aa1e0a6318756df692cc13df2cc83"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c89845fae250efdd59c1d4ec60e9e1c652cee4b6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d33f89b34aa313f50f9a512d58dd288999f246b0"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Deferred"
}


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