Vulnerability-Lookup

GHSA-HJWG-8C2J-JQ5P

Vulnerability from github – Published: 2026-05-08 15:31 – Updated: 2026-05-08 15:31

Details

In the Linux kernel, the following vulnerability has been resolved:

sched/mmcid: Handle vfork()/CLONE_VM correctly

Matthieu and Jiri reported stalls where a task endlessly loops in mm_get_cid() when scheduling in.

It turned out that the logic which handles vfork()'ed tasks is broken. It is invoked when the number of tasks associated to a process is smaller than the number of MMCID users. It then walks the task list to find the vfork()'ed task, but accounts all the already processed tasks as well.

If that double processing brings the number of to be handled tasks to 0, the walk stops and the vfork()'ed task's CID is not fixed up. As a consequence a subsequent schedule in fails to acquire a (transitional) CID and the machine stalls.

Cure this by removing the accounting condition and make the fixup always walk the full task list if it could not find the exact number of users in the process' thread list.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-43417"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-08T15:16:53Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/mmcid: Handle vfork()/CLONE_VM correctly\n\nMatthieu and Jiri reported stalls where a task endlessly loops in\nmm_get_cid() when scheduling in.\n\nIt turned out that the logic which handles vfork()\u0027ed tasks is broken. It\nis invoked when the number of tasks associated to a process is smaller than\nthe number of MMCID users. It then walks the task list to find the\nvfork()\u0027ed task, but accounts all the already processed tasks as well.\n\nIf that double processing brings the number of to be handled tasks to 0,\nthe walk stops and the vfork()\u0027ed task\u0027s CID is not fixed up. As a\nconsequence a subsequent schedule in fails to acquire a (transitional) CID\nand the machine stalls.\n\nCure this by removing the accounting condition and make the fixup always\nwalk the full task list if it could not find the exact number of users in\nthe process\u0027 thread list.",
  "id": "GHSA-hjwg-8c2j-jq5p",
  "modified": "2026-05-08T15:31:28Z",
  "published": "2026-05-08T15:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43417"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/28b5a1395036d6c7a6c8034d85ad3d7d365f192c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e6761cdce78a8919a537989afb6aaf6881469f83"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-43417 (GCVE-0-2026-43417)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:21 – Updated: 2026-05-11 22:24

Title

sched/mmcid: Handle vfork()/CLONE_VM correctly

Summary

In the Linux kernel, the following vulnerability has been resolved: sched/mmcid: Handle vfork()/CLONE_VM correctly Matthieu and Jiri reported stalls where a task endlessly loops in mm_get_cid() when scheduling in. It turned out that the logic which handles vfork()'ed tasks is broken. It is invoked when the number of tasks associated to a process is smaller than the number of MMCID users. It then walks the task list to find the vfork()'ed task, but accounts all the already processed tasks as well. If that double processing brings the number of to be handled tasks to 0, the walk stops and the vfork()'ed task's CID is not fixed up. As a consequence a subsequent schedule in fails to acquire a (transitional) CID and the machine stalls. Cure this by removing the accounting condition and make the fixup always walk the full task list if it could not find the exact number of users in the process' thread list.

Severity

No CVSS data available.

Assigner

Linux

References

2 references

URL	Tags
https://git.kernel.org/stable/c/e6761cdce78a8919a…
https://git.kernel.org/stable/c/28b5a1395036d6c7a…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: fbd0e71dc370af73f6b316e4de9eed273dd90340 , < e6761cdce78a8919a537989afb6aaf6881469f83 (git) Affected: fbd0e71dc370af73f6b316e4de9eed273dd90340 , < 28b5a1395036d6c7a6c8034d85ad3d7d365f192c (git)
Linux	Linux	Affected: 6.19 Unaffected: 0 , < 6.19 (semver) Unaffected: 6.19.9 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix)

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  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e6761cdce78a8919a537989afb6aaf6881469f83",
              "status": "affected",
              "version": "fbd0e71dc370af73f6b316e4de9eed273dd90340",
              "versionType": "git"
            },
            {
              "lessThan": "28b5a1395036d6c7a6c8034d85ad3d7d365f192c",
              "status": "affected",
              "version": "fbd0e71dc370af73f6b316e4de9eed273dd90340",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                }
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              "operator": "OR"
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        }
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/mmcid: Handle vfork()/CLONE_VM correctly\n\nMatthieu and Jiri reported stalls where a task endlessly loops in\nmm_get_cid() when scheduling in.\n\nIt turned out that the logic which handles vfork()\u0027ed tasks is broken. It\nis invoked when the number of tasks associated to a process is smaller than\nthe number of MMCID users. It then walks the task list to find the\nvfork()\u0027ed task, but accounts all the already processed tasks as well.\n\nIf that double processing brings the number of to be handled tasks to 0,\nthe walk stops and the vfork()\u0027ed task\u0027s CID is not fixed up. As a\nconsequence a subsequent schedule in fails to acquire a (transitional) CID\nand the machine stalls.\n\nCure this by removing the accounting condition and make the fixup always\nwalk the full task list if it could not find the exact number of users in\nthe process\u0027 thread list."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:24:11.172Z",
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        {
          "url": "https://git.kernel.org/stable/c/28b5a1395036d6c7a6c8034d85ad3d7d365f192c"
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      "title": "sched/mmcid: Handle vfork()/CLONE_VM correctly",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43417",
    "datePublished": "2026-05-08T14:21:53.618Z",
    "dateReserved": "2026-05-01T14:12:56.008Z",
    "dateUpdated": "2026-05-11T22:24:11.172Z",
    "state": "PUBLISHED"
  },
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Sightings

Author	Source	Type	Date	Other

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.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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.

Action not permitted

GHSA-HJWG-8C2J-JQ5P

CVE-2026-43417 (GCVE-0-2026-43417)

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Nomenclature