fkie_cve-2024-47740
Vulnerability from fkie_nvd
Published
2024-10-21 13:15
Modified
2025-10-08 17:03
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: Require FMODE_WRITE for atomic write ioctls The F2FS ioctls for starting and committing atomic writes check for inode_owner_or_capable(), but this does not give LSMs like SELinux or Landlock an opportunity to deny the write access - if the caller's FSUID matches the inode's UID, inode_owner_or_capable() immediately returns true. There are scenarios where LSMs want to deny a process the ability to write particular files, even files that the FSUID of the process owns; but this can currently partially be bypassed using atomic write ioctls in two ways: - F2FS_IOC_START_ATOMIC_REPLACE + F2FS_IOC_COMMIT_ATOMIC_WRITE can truncate an inode to size 0 - F2FS_IOC_START_ATOMIC_WRITE + F2FS_IOC_ABORT_ATOMIC_WRITE can revert changes another process concurrently made to a file Fix it by requiring FMODE_WRITE for these operations, just like for F2FS_IOC_MOVE_RANGE. Since any legitimate caller should only be using these ioctls when intending to write into the file, that seems unlikely to break anything.



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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: Require FMODE_WRITE for atomic write ioctls\n\nThe F2FS ioctls for starting and committing atomic writes check for\ninode_owner_or_capable(), but this does not give LSMs like SELinux or\nLandlock an opportunity to deny the write access - if the caller\u0027s FSUID\nmatches the inode\u0027s UID, inode_owner_or_capable() immediately returns true.\n\nThere are scenarios where LSMs want to deny a process the ability to write\nparticular files, even files that the FSUID of the process owns; but this\ncan currently partially be bypassed using atomic write ioctls in two ways:\n\n - F2FS_IOC_START_ATOMIC_REPLACE + F2FS_IOC_COMMIT_ATOMIC_WRITE can\n   truncate an inode to size 0\n - F2FS_IOC_START_ATOMIC_WRITE + F2FS_IOC_ABORT_ATOMIC_WRITE can revert\n   changes another process concurrently made to a file\n\nFix it by requiring FMODE_WRITE for these operations, just like for\nF2FS_IOC_MOVE_RANGE. Since any legitimate caller should only be using these\nioctls when intending to write into the file, that seems unlikely to break\nanything."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: f2fs: Requerir FMODE_WRITE para ioctls de escritura at\u00f3mica Los ioctls de F2FS para iniciar y confirmar escrituras at\u00f3micas comprueban inode_owner_or_capable(), pero esto no da a los LSM como SELinux o Landlock la oportunidad de denegar el acceso de escritura: si el FSUID del llamador coincide con el UID del inodo, inode_owner_or_capable() devuelve verdadero inmediatamente. Hay escenarios en los que los LSM quieren denegar a un proceso la capacidad de escribir archivos particulares, incluso archivos que el FSUID del proceso posee; pero esto actualmente se puede omitir parcialmente usando ioctls de escritura at\u00f3mica de dos maneras: - F2FS_IOC_START_ATOMIC_REPLACE + F2FS_IOC_COMMIT_ATOMIC_WRITE puede truncar un inodo a tama\u00f1o 0 - F2FS_IOC_START_ATOMIC_WRITE + F2FS_IOC_ABORT_ATOMIC_WRITE puede revertir los cambios que otro proceso realiz\u00f3 simult\u00e1neamente en un archivo Arr\u00e9glelo requiriendo FMODE_WRITE para estas operaciones, al igual que para F2FS_IOC_MOVE_RANGE. Dado que cualquier llamador leg\u00edtimo solo debe usar estos ioctls cuando tenga la intenci\u00f3n de escribir en el archivo, parece poco probable que eso rompa algo."
    }
  ],
  "id": "CVE-2024-47740",
  "lastModified": "2025-10-08T17:03:47.850",
  "metrics": {
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          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
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        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
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  "published": "2024-10-21T13:15:04.103",
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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          "lang": "en",
          "value": "NVD-CWE-noinfo"
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      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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