GHSA-PGCJ-5WJ3-JCMR

Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 15:31
VLAI
Details

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

s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed

The vfio_ap_mdev_hot_unplug_cfg() function uses the return value of bitmap_andnot() to determine whether the guest APCB needs to be updated. However, bitmap_andnot() returns false when the resulting destination bitmap is empty. This means that if the only adapter, domain or control domain assigned to an mdev is removed from the host's AP configuration, the bit is correctly cleared from the shadow APCB, but bitmap_andnot() returns false because the result is an empty bitmap. Consequently, do_hotplug remains 0 and vfio_ap_mdev_update_guest_apcb() is never called, leaving the KVM guest with stale hardware access to the unplugged AP devices.

Fix this by replacing the bitmap_andnot() return value check with bitmap_intersects() to determine whether the shadow APCB actually overlaps with the removal mask. If there is an intersection, call bitmap_andnot() solely for its side effect of clearing the bits, then unconditionally set do_hotplug to trigger the guest APCB update.

Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89957"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T11:17:06Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed\n\nThe vfio_ap_mdev_hot_unplug_cfg() function uses the return value of\nbitmap_andnot() to determine whether the guest APCB needs to be updated.\nHowever, bitmap_andnot() returns false when the resulting destination\nbitmap is empty. This means that if the only adapter, domain or control\ndomain assigned to an mdev is removed from the host\u0027s AP configuration,\nthe bit is correctly cleared from the shadow APCB, but bitmap_andnot()\nreturns false because the result is an empty bitmap. Consequently,\ndo_hotplug remains 0 and vfio_ap_mdev_update_guest_apcb() is never called,\nleaving the KVM guest with stale hardware access to the unplugged AP\ndevices.\n\nFix this by replacing the bitmap_andnot() return value check with\nbitmap_intersects() to determine whether the shadow APCB actually\noverlaps with the removal mask. If there is an intersection, call\nbitmap_andnot() solely for its side effect of clearing the bits, then\nunconditionally set do_hotplug to trigger the guest APCB update.",
  "id": "GHSA-pgcj-5wj3-jcmr",
  "modified": "2026-09-16T15:31:03Z",
  "published": "2026-09-16T12:30:43Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89957"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/04b35dd88c108b2d2ceaaa396aba1cb4049d5831"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3a9b049bbdc40165d7f3e20b818eec95e5694d96"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/753aa3bb1273bc0d36adb013d5915cc8ff6b72a9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/917f509bfb88048094dbb85c4e9dbc4d6fe4a886"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c45753c32d452d10d8efaeb52587e9e6e8126e33"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f58e824de8577fe411f6199d659731a0f86a7275"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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