FKIE_CVE-2021-47640

Vulnerability from fkie_nvd - Published: 2025-02-26 06:37 - Updated: 2026-06-17 04:18
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: powerpc/kasan: Fix early region not updated correctly The shadow's page table is not updated when PTE_RPN_SHIFT is 24 and PAGE_SHIFT is 12. It not only causes false positives but also false negative as shown the following text. Fix it by bringing the logic of kasan_early_shadow_page_entry here. 1. False Positive: ================================================================== BUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50 Write of size 16 at addr f57f3be0 by task swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1 Call Trace: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Memory state around the buggy address: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ================================================================== 2. False Negative (with KASAN tests): ================================================================== Before fix: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039 KASAN failure expected in "((volatile char *)area)[3100]", but none occurred not ok 46 - vmalloc_oob not ok 1 - kasan ================================================================== After fix: ok 1 - kasan
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519dPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/powerpc/mm/kasan/kasan_init_32.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "7f19245c3647afea8c7c41f795506ef70f64b9f2",
              "status": "affected",
              "version": "cbd18991e24fea2c31da3bb117c83e4a3538cd11",
              "versionType": "git"
            },
            {
              "lessThan": "f39a3309393a4a484532f6ba745c6acbcfe06115",
              "status": "affected",
              "version": "cbd18991e24fea2c31da3bb117c83e4a3538cd11",
              "versionType": "git"
            },
            {
              "lessThan": "5a3d8f3192a409893c57808cc935e16484df1068",
              "status": "affected",
              "version": "cbd18991e24fea2c31da3bb117c83e4a3538cd11",
              "versionType": "git"
            },
            {
              "lessThan": "de56beace6648065d404cd9835aa7d30e3df519d",
              "status": "affected",
              "version": "cbd18991e24fea2c31da3bb117c83e4a3538cd11",
              "versionType": "git"
            },
            {
              "lessThan": "e3d157a4b4f4e0268c98be5b7013bf4b31234bb6",
              "status": "affected",
              "version": "cbd18991e24fea2c31da3bb117c83e4a3538cd11",
              "versionType": "git"
            },
            {
              "lessThan": "dd75080aa8409ce10d50fb58981c6b59bf8707d3",
              "status": "affected",
              "version": "cbd18991e24fea2c31da3bb117c83e4a3538cd11",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "3822dd8c102d11ada9d9ed8e04cad0b347a04689",
              "versionType": "git"
            },
            {
              "lessThan": "5.4",
              "status": "affected",
              "version": "5.3.6",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/powerpc/mm/kasan/kasan_init_32.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.4"
            },
            {
              "lessThan": "5.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.4.*",
              "status": "unaffected",
              "version": "5.4.189",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.33",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.16.*",
              "status": "unaffected",
              "version": "5.16.19",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.17.*",
              "status": "unaffected",
              "version": "5.17.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "5.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "80DDFBB5-E7D8-4F00-9608-47CCB8D46CA4",
              "versionEndExcluding": "5.4.189",
              "versionStartIncluding": "5.4",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "91D3BFD0-D3F3-4018-957C-96CCBF357D79",
              "versionEndExcluding": "5.10.110",
              "versionStartIncluding": "5.5",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "27C42AE8-B387-43E2-938A-E1C8B40BE6D5",
              "versionEndExcluding": "5.15.33",
              "versionStartIncluding": "5.11",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "20C43679-0439-405A-B97F-685BEE50613B",
              "versionEndExcluding": "5.16.19",
              "versionStartIncluding": "5.16",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "210C679C-CF84-44A3-8939-E629C87E54BF",
              "versionEndExcluding": "5.17.2",
              "versionStartIncluding": "5.17",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/kasan: Fix early region not updated correctly\n\nThe shadow\u0027s page table is not updated when PTE_RPN_SHIFT is 24\nand PAGE_SHIFT is 12. It not only causes false positives but\nalso false negative as shown the following text.\n\nFix it by bringing the logic of kasan_early_shadow_page_entry here.\n\n1. False Positive:\n==================================================================\nBUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50\nWrite of size 16 at addr f57f3be0 by task swapper/0/1\n\nCPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1\nCall Trace:\n[c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable)\n[c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300\n[c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200\n[c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0\n[c80d1cc0] [c03018a4] memset+0x34/0x90\n[c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50\n[c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570\n[c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0\n[c80d1db0] [c2036580] init_sd+0xc4/0x1d0\n[c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c\n[c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384\n[c80d1ef0] [c0004b14] kernel_init+0x24/0x170\n[c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64\n\nMemory state around the buggy address:\n f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n\u003ef57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n                                               ^\n f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n==================================================================\n\n2. False Negative (with KASAN tests):\n==================================================================\nBefore fix:\n    ok 45 - kmalloc_double_kzfree\n    # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039\n    KASAN failure expected in \"((volatile char *)area)[3100]\", but none occurred\n    not ok 46 - vmalloc_oob\n    not ok 1 - kasan\n\n==================================================================\nAfter fix:\n    ok 1 - kasan"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: powerpc/kasan: Se solucion\u00f3 que la regi\u00f3n temprana no se actualizara correctamente La tabla de p\u00e1ginas de shadow no se actualiza cuando PTE_RPN_SHIFT es 24 y PAGE_SHIFT es 12. No solo causa falsos positivos sino tambi\u00e9n falsos negativos como se muestra en el siguiente texto. Arr\u00e9glelo trayendo la l\u00f3gica de kasan_early_shadow_page_entry aqu\u00ed. 1. Falso positivo: ==================================================================== ERROR: KASAN: vmalloc fuera de los l\u00edmites en pcpu_alloc+0x508/0xa50 Escritura de tama\u00f1o 16 en la direcci\u00f3n f57f3be0 por la tarea swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 No contaminado 5.15.0-12267-gdebe436e77c7 #1 Seguimiento de llamadas: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (no confiable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Estado de la memoria alrededor de la direcci\u00f3n con errores: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 \u0026gt;f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ===================================================================== 2. Falso negativo (con pruebas KASAN): ==================================================================== Antes de la correcci\u00f3n: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATIVA FALL\u00d3 en lib/test_kasan.c:1039 Se esperaba una falla de KASAN en \"((volatile char *)area)[3100]\", pero no ocurri\u00f3 ninguna no ok 46 - vmalloc_oob no ok 1 - kasan ======================================================================== Despu\u00e9s de la correcci\u00f3n: ok 1 - kasan"
    }
  ],
  "id": "CVE-2021-47640",
  "lastModified": "2026-06-17T04:18:13.227",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "nvd@nist.gov",
        "type": "Primary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-47640",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2025-10-01T19:50:44.222623Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2025-02-26T06:37:05.780",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    },
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary"
    }
  ]
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.