CVE-2021-47491 (GCVE-0-2021-47491)

Vulnerability from cvelistv5 – Published: 2024-05-22 08:19 – Updated: 2026-05-11 13:55
VLAI
Title
mm: khugepaged: skip huge page collapse for special files
Summary
In the Linux kernel, the following vulnerability has been resolved: mm: khugepaged: skip huge page collapse for special files The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@gmail.com: fix vm_file check [3]]
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-05-22 18:42 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 , < 6d67b2a73b8e3a079c355bab3c1aef7d85a044b8 (git)
Affected: 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 , < 5fcb6fce74ffa614d964667110cf1a516c48c6d9 (git)
Affected: 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 , < a4aeaa06d45e90f9b279f0b09de84bd00006e733 (git)
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Linux Linux Affected: 5.4
Unaffected: 0 , < 5.4 (semver)
Unaffected: 5.10.78 , ≤ 5.10.* (semver)
Unaffected: 5.14.16 , ≤ 5.14.* (semver)
Unaffected: 5.15 , ≤ * (original_commit_for_fix)
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Show details on NVD website
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      "version": "3"
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      "current_release_date": "2026-10-21T01:02:53Z",
      "cve": "CVE-2021-47491",
      "id": "CVE-2021-47491",
      "initial_release_date": "2024-05-23T03:04:25Z",
      "product_status:known_affected": "0",
      "product_status:known_not_affected": "263",
      "product_status:recommended": "353",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-47491",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2024/cve-2021-47491.json",
      "version": "40"
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              "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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              }
            ],
            "title": "CVE Program Container"
          },
          {
            "metrics": [
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                "other": {
                  "content": {
                    "id": "CVE-2021-47491",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2024-05-22T18:42:55.199651Z",
                    "version": "2.0.3"
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              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
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        ],
        "cna": {
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              "product": "Linux",
              "programFiles": [
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              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
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                  "status": "affected",
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                },
                {
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                  "version": "0",
                  "versionType": "semver"
                },
                {
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                {
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                {
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                  "status": "unaffected",
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                  "operator": "OR"
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          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: khugepaged: skip huge page collapse for special files\n\nThe read-only THP for filesystems will collapse THP for files opened\nreadonly and mapped with VM_EXEC.  The intended usecase is to avoid TLB\nmisses for large text segments.  But it doesn\u0027t restrict the file types\nso a THP could be collapsed for a non-regular file, for example, block\ndevice, if it is opened readonly and mapped with EXEC permission.  This\nmay cause bugs, like [1] and [2].\n\nThis is definitely not the intended usecase, so just collapse THP for\nregular files in order to close the attack surface.\n\n[shy828301@gmail.com: fix vm_file check [3]]"
            }
          ],
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            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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            },
            {
              "url": "https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733"
            }
          ],
          "title": "mm: khugepaged: skip huge page collapse for special files",
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      "cveMetadata": {
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        "assignerShortName": "Linux",
        "cveId": "CVE-2021-47491",
        "datePublished": "2024-05-22T08:19:40.101Z",
        "dateReserved": "2024-05-22T06:20:56.201Z",
        "dateUpdated": "2025-05-04T07:12:11.704Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



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Sightings

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