fkie_cve-2021-47450
Vulnerability from fkie_nvd
Published
2024-05-22 07:15
Modified
2025-09-24 01:07
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: KVM: arm64: Fix host stage-2 PGD refcount The KVM page-table library refcounts the pages of concatenated stage-2 PGDs individually. However, when running KVM in protected mode, the host's stage-2 PGD is currently managed by EL2 as a single high-order compound page, which can cause the refcount of the tail pages to reach 0 when they shouldn't, hence corrupting the page-table. Fix this by introducing a new hyp_split_page() helper in the EL2 page allocator (matching the kernel's split_page() function), and make use of it from host_s2_zalloc_pages_exact().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b372264c66ef78f2cab44e877fbd765ad6d24c39Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/b372264c66ef78f2cab44e877fbd765ad6d24c39Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel 5.15
linux linux_kernel 5.15
linux linux_kernel 5.15
linux linux_kernel 5.15
linux linux_kernel 5.15
linux linux_kernel 5.15


To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "5B5C2D1A-B435-4D41-8BF1-CC189296494D",
              "versionEndExcluding": "5.14.15",
              "versionStartIncluding": "5.13",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:*",
              "matchCriteriaId": "E46C74C6-B76B-4C94-A6A4-FD2FFF62D644",
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          "negate": false,
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Fix host stage-2 PGD refcount\n\nThe KVM page-table library refcounts the pages of concatenated stage-2\nPGDs individually. However, when running KVM in protected mode, the\nhost\u0027s stage-2 PGD is currently managed by EL2 as a single high-order\ncompound page, which can cause the refcount of the tail pages to reach 0\nwhen they shouldn\u0027t, hence corrupting the page-table.\n\nFix this by introducing a new hyp_split_page() helper in the EL2 page\nallocator (matching the kernel\u0027s split_page() function), and make use of\nit from host_s2_zalloc_pages_exact()."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: KVM: arm64: corrige el recuento de PGD de etapa 2 del host La librer\u00eda de tablas de p\u00e1ginas de KVM vuelve a contar las p\u00e1ginas de los PGD de etapa 2 concatenados individualmente. Sin embargo, cuando se ejecuta KVM en modo protegido, EL2 administra actualmente el PGD de etapa 2 del host como una \u00fanica p\u00e1gina compuesta de alto orden, lo que puede causar que el recuento de las p\u00e1ginas finales llegue a 0 cuando no deber\u00eda, corrompiendo as\u00ed el tabla de p\u00e1ginas. Solucione este problema introduciendo un nuevo asistente hyp_split_page() en el asignador de p\u00e1ginas EL2 (que coincida con la funci\u00f3n split_page() del kernel) y util\u00edcelo desde host_s2_zalloc_pages_exact()."
    }
  ],
  "id": "CVE-2021-47450",
  "lastModified": "2025-09-24T01:07:53.987",
  "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": "2024-05-22T07:15:10.143",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1"
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      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
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    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-Other"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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