GHSA-8G2P-P68F-4WQR

Vulnerability from github – Published: 2024-05-22 09:31 – Updated: 2025-09-29 18:33
VLAI?
Details

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 ?
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2021-47491"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-05-22T09:15:10Z",
    "severity": "MODERATE"
  },
  "details": "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]]",
  "id": "GHSA-8g2p-p68f-4wqr",
  "modified": "2025-09-29T18:33:07Z",
  "published": "2024-05-22T09:31:46Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47491"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5fcb6fce74ffa614d964667110cf1a516c48c6d9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6d67b2a73b8e3a079c355bab3c1aef7d85a044b8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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