FKIE_CVE-2026-43417

Vulnerability from fkie_nvd - Published: 2026-05-08 15:16 - Updated: 2026-05-12 14:10
Severity
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/28b5a1395036d6c7a6c8034d85ad3d7d365f192c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e6761cdce78a8919a537989afb6aaf6881469f83
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{
  "cveTags": [],
  "descriptions": [
    {
      "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."
    }
  ],
  "id": "CVE-2026-43417",
  "lastModified": "2026-05-12T14:10:27.343",
  "metrics": {},
  "published": "2026-05-08T15:16:53.700",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/28b5a1395036d6c7a6c8034d85ad3d7d365f192c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e6761cdce78a8919a537989afb6aaf6881469f83"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Undergoing Analysis"
}


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