fkie_cve-2025-37949
Vulnerability from fkie_nvd
Published
2025-05-20 16:15
Modified
2025-12-17 20:05
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: xenbus: Use kref to track req lifetime Marek reported seeing a NULL pointer fault in the xenbus_thread callstack: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: e030:__wake_up_common+0x4c/0x180 Call Trace: <TASK> __wake_up_common_lock+0x82/0xd0 process_msg+0x18e/0x2f0 xenbus_thread+0x165/0x1c0 process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems like it was xs_wake_up() in this case. It seems like req may have woken up the xs_wait_for_reply(), which kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed data. Linux Device Drivers 2nd edition states: "Normally, a wake_up call can cause an immediate reschedule to happen, meaning that other processes might run before wake_up returns." ... which would match the behaviour observed. Change to keeping two krefs on each request. One for the caller, and one for xenbus_thread. Each will kref_put() when finished, and the last will free it. This use of kref matches the description in Documentation/core-api/kref.rst
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0e94a246bb6d9538010b6c02d2b1d4717a97b2e5Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2466b0f66795c3c426cacc8998499f38031dbb59Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4d260a5558df4650eb87bc41b2c9ac2d6b2ba447Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8b02f85e84dc6f7c150cef40ddb69af5a25659e5Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8e9c8a0393b5f85f1820c565ab8105660f4e8f92Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cbfaf46b88a4c01b64c4186cdccd766c19ae644cPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f1bcac367bc95631afbb918348f30dec887d0e1bPatch
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/08/msg00010.htmlThird Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlThird Party Advisory
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 6.15
linux linux_kernel 6.15
linux linux_kernel 6.15
linux linux_kernel 6.15
linux linux_kernel 6.15
debian debian_linux 11.0


To clipboard 

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    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxenbus: Use kref to track req lifetime\n\nMarek reported seeing a NULL pointer fault in the xenbus_thread\ncallstack:\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nRIP: e030:__wake_up_common+0x4c/0x180\nCall Trace:\n \u003cTASK\u003e\n __wake_up_common_lock+0x82/0xd0\n process_msg+0x18e/0x2f0\n xenbus_thread+0x165/0x1c0\n\nprocess_msg+0x18e is req-\u003ecb(req).  req-\u003ecb is set to xs_wake_up(), a\nthin wrapper around wake_up(), or xenbus_dev_queue_reply().  It seems\nlike it was xs_wake_up() in this case.\n\nIt seems like req may have woken up the xs_wait_for_reply(), which\nkfree()ed the req.  When xenbus_thread resumes, it faults on the zero-ed\ndata.\n\nLinux Device Drivers 2nd edition states:\n\"Normally, a wake_up call can cause an immediate reschedule to happen,\nmeaning that other processes might run before wake_up returns.\"\n... which would match the behaviour observed.\n\nChange to keeping two krefs on each request.  One for the caller, and\none for xenbus_thread.  Each will kref_put() when finished, and the last\nwill free it.\n\nThis use of kref matches the description in\nDocumentation/core-api/kref.rst"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: xenbus: Usar kref para rastrear el tiempo de vida de req. Marek inform\u00f3 haber visto un fallo de puntero nulo en la pila de llamadas xenbus_thread: ERROR: desreferencia de puntero nulo del kernel, direcci\u00f3n: 0000000000000000 RIP: e030:__wake_up_common+0x4c/0x180 Rastreo de llamadas:  __wake_up_common_lock+0x82/0xd0 process_msg+0x18e/0x2f0 xenbus_thread+0x165/0x1c0 process_msg+0x18e es req-\u0026gt;cb(req). req-\u0026gt;cb est\u00e1 configurado como xs_wake_up(), una envoltura ligera alrededor de wake_up(), o xenbus_dev_queue_reply(). Parece que en este caso era xs_wake_up(). Parece que req pudo haber despertado xs_wait_for_reply(), que liber\u00f3 la solicitud. Cuando xenbus_thread se reanuda, falla en los datos con ceros. La segunda edici\u00f3n de los controladores de dispositivos de Linux indica: \u00abNormalmente, una llamada wake_up puede provocar una reprogramaci\u00f3n inmediata, lo que significa que otros procesos podr\u00edan ejecutarse antes de que wake_up regrese\u00bb. ... lo cual coincidir\u00eda con el comportamiento observado. Se recomienda mantener dos krefs en cada solicitud: uno para el que realiza la llamada y otro para xenbus_thread. Cada uno ejecutar\u00e1 kref_put() al finalizar, y el \u00faltimo lo liberar\u00e1. Este uso de kref coincide con la descripci\u00f3n en Documentation/core-api/kref.rst."
    }
  ],
  "id": "CVE-2025-37949",
  "lastModified": "2025-12-17T20:05:13.020",
  "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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        "impactScore": 3.6,
        "source": "nvd@nist.gov",
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  "published": "2025-05-20T16:15:32.920",
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          "value": "CWE-476"
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      "source": "nvd@nist.gov",
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}


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