fkie_cve-2025-38282
Vulnerability from fkie_nvd
Published
2025-07-10 08:15
Modified
2025-12-18 16:50
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: kernfs: Relax constraint in draining guard The active reference lifecycle provides the break/unbreak mechanism but the active reference is not truly active after unbreak -- callers don't use it afterwards but it's important for proper pairing of kn->active counting. Assuming this mechanism is in place, the WARN check in kernfs_should_drain_open_files() is too sensitive -- it may transiently catch those (rightful) callers between kernfs_unbreak_active_protection() and kernfs_put_active() as found out by Chen Ridong: kernfs_remove_by_name_ns kernfs_get_active // active=1 __kernfs_remove // active=0x80000002 kernfs_drain ... wait_event //waiting (active == 0x80000001) kernfs_break_active_protection // active = 0x80000001 // continue kernfs_unbreak_active_protection // active = 0x80000002 ... kernfs_should_drain_open_files // warning occurs kernfs_put_active To avoid the false positives (mind panic_on_warn) remove the check altogether. (This is meant as quick fix, I think active reference break/unbreak may be simplified with larger rework.)
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/071d8e4c2a3b0999a9b822e2eb8854784a350f8aPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2d6a67c2b3b87808a347dc1047b520a9dd177a4fPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6bfb154f95d5f0ab7ed056f23aba8c1a94cb3927Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6c81f1c7812c61f187bed1b938f1d2e391d503abPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/72275c888f8962b406ee9c6885c79bf68cca5a63Patch
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlThird Party Advisory, Mailing List
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
debian debian_linux 11.0


To clipboard 

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  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkernfs: Relax constraint in draining guard\n\nThe active reference lifecycle provides the break/unbreak mechanism but\nthe active reference is not truly active after unbreak -- callers don\u0027t\nuse it afterwards but it\u0027s important for proper pairing of kn-\u003eactive\ncounting. Assuming this mechanism is in place, the WARN check in\nkernfs_should_drain_open_files() is too sensitive -- it may transiently\ncatch those (rightful) callers between\nkernfs_unbreak_active_protection() and kernfs_put_active() as found out by Chen\nRidong:\n\n\tkernfs_remove_by_name_ns\tkernfs_get_active // active=1\n\t__kernfs_remove\t\t\t\t\t  // active=0x80000002\n\tkernfs_drain\t\t\t...\n\twait_event\n\t//waiting (active == 0x80000001)\n\t\t\t\t\tkernfs_break_active_protection\n\t\t\t\t\t// active = 0x80000001\n\t// continue\n\t\t\t\t\tkernfs_unbreak_active_protection\n\t\t\t\t\t// active = 0x80000002\n\t...\n\tkernfs_should_drain_open_files\n\t// warning occurs\n\t\t\t\t\tkernfs_put_active\n\nTo avoid the false positives (mind panic_on_warn) remove the check altogether.\n(This is meant as quick fix, I think active reference break/unbreak may be\nsimplified with larger rework.)"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: kernfs: relajar restricci\u00f3n en el drenaje de la protecci\u00f3n El ciclo de vida de la referencia activa proporciona el mecanismo de interrupci\u00f3n/desconexi\u00f3n, pero la referencia activa no est\u00e1 verdaderamente activa despu\u00e9s de la conexi\u00f3n; los llamadores no la usan despu\u00e9s, pero es importante para el emparejamiento adecuado del conteo kn-\u0026gt;activo. Suponiendo que este mecanismo est\u00e1 en su lugar, la comprobaci\u00f3n WARN en kernfs_should_drain_open_files() es demasiado sensible - puede atrapar transitoriamente a aquellos llamadores (leg\u00edtimos) entre kernfs_unbreak_active_protection() y kernfs_put_active() como descubri\u00f3 Chen Ridong: kernfs_remove_by_name_ns kernfs_get_active // active=1 __kernfs_remove // active=0x80000002 kernfs_drain ... wait_event //waiting (active == 0x80000001) kernfs_break_active_protection // active = 0x80000001 // continuar kernfs_unbreak_active_protection // active = 0x80000002 ... kernfs_should_drain_open_files // ocurre una advertencia kernfs_put_active Para evitar los falsos positivos (tenga en cuenta \"panic_on_warn\"), elimine la comprobaci\u00f3n por completo. (Esto es una soluci\u00f3n r\u00e1pida; creo que la interrupci\u00f3n/desconexi\u00f3n de referencias activas se puede simplificar con una revisi\u00f3n m\u00e1s exhaustiva)."
    }
  ],
  "id": "CVE-2025-38282",
  "lastModified": "2025-12-18T16:50:33.577",
  "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",
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  "published": "2025-07-10T08:15:26.610",
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}


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