fkie_cve-2021-46990
Vulnerability from fkie_nvd
Published
2024-02-28 09:15
Modified
2024-12-26 15:01
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: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations. However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash: sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore). Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0b4eb172cc12dc102cd0ad013e53ee4463db9508Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0c25a7bb697f2e6ee65b6d63782f675bf129511aPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2db22ba4e0e103f00e0512e0ecce36ac78c644f8Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5bc00fdda1e934c557351a9c751a205293e68cbfPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8382b15864e5014261b4f36c2aa89723612ee058Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/aec86b052df6541cc97c5fca44e5934cbea4963bPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dd0d6117052faace5440db20fc37175efe921c7dPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ee4b7aab93c2631c3bb0753023c5dda592bb666bPatch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/0b4eb172cc12dc102cd0ad013e53ee4463db9508Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/0c25a7bb697f2e6ee65b6d63782f675bf129511aPatch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/2db22ba4e0e103f00e0512e0ecce36ac78c644f8Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/5bc00fdda1e934c557351a9c751a205293e68cbfPatch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/8382b15864e5014261b4f36c2aa89723612ee058Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/aec86b052df6541cc97c5fca44e5934cbea4963bPatch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/dd0d6117052faace5440db20fc37175efe921c7dPatch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/ee4b7aab93c2631c3bb0753023c5dda592bb666bPatch
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 *
linux linux_kernel 5.13


To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
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          "negate": false,
          "operator": "OR"
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/64s: Fix crashes when toggling entry flush barrier\n\nThe entry flush mitigation can be enabled/disabled at runtime via a\ndebugfs file (entry_flush), which causes the kernel to patch itself to\nenable/disable the relevant mitigations.\n\nHowever depending on which mitigation we\u0027re using, it may not be safe to\ndo that patching while other CPUs are active. For example the following\ncrash:\n\n  sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20\n\nShows that we returned to userspace with a corrupted LR that points into\nthe kernel, due to executing the partially patched call to the fallback\nentry flush (ie. we missed the LR restore).\n\nFix it by doing the patching under stop machine. The CPUs that aren\u0027t\ndoing the patching will be spinning in the core of the stop machine\nlogic. That is currently sufficient for our purposes, because none of\nthe patching we do is to that code or anywhere in the vicinity."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: powerpc/64s: soluciona fallas al alternar la barrera de descarga de entrada. La mitigaci\u00f3n de descarga de entrada se puede habilitar/deshabilitar en tiempo de ejecuci\u00f3n a trav\u00e9s de un archivo debugfs (entry_flush), lo que hace que el kernel se parchee a s\u00ed mismo. habilitar/deshabilitar las mitigaciones relevantes. Sin embargo, dependiendo de la mitigaci\u00f3n que estemos usando, puede que no sea seguro aplicar ese parche mientras otras CPU est\u00e1n activas. Por ejemplo, el siguiente bloqueo: durmiente[15639]: segfault (11) en c000000000004c20 nip c000000000004c20 lr c000000000004c20 Muestra que regresamos al espacio de usuario con un LR corrupto que apunta al kernel, debido a la ejecuci\u00f3n de la llamada parcialmente parcheada a la entrada de respaldo descarga ( es decir, nos perdimos la restauraci\u00f3n de LR). Arr\u00e9glelo haciendo el parche debajo de detener la m\u00e1quina. Las CPU que no est\u00e9n aplicando los parches girar\u00e1n en el n\u00facleo de la l\u00f3gica de detenci\u00f3n de la m\u00e1quina. Actualmente, eso es suficiente para nuestros prop\u00f3sitos, porque ninguno de los parches que hacemos se aplica a ese c\u00f3digo ni a ning\u00fan lugar cercano."
    }
  ],
  "id": "CVE-2021-46990",
  "lastModified": "2024-12-26T15:01:41.753",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "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"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2024-02-28T09:15:37.733",
  "references": [
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  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "description": [
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          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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