{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects  In order to traverse or add/remove ap_matrix_mdev objects in the matrix_dev-\u003emdev_list, the matrix_dev-\u003eguests_lock mutex must be held. There are two functions that access the list without holding the mutex:  vfio_ap_mdev_probe function ~~~~~~~~~~~~~~~~~~~~~~~~~~~ The vfio_ap_mdev_probe function uses the matrix_dev-\u003emdevs_lock mutex to guard the add of a newly created ap_matrix_mdev object to the matrix_dev-\u003emdev_list. This mutex does not protect list access; its purpose is to guard against concurrent access to fields contained in an ap_matrix_mdev object. This could lead to kernel memory corruption or use-after-free if another mdev is created or removed concurrently.  The adding of an ap_matrix_mdev object to matrix_dev-\u003emdev_list is now guarded by the matrix_dev-\u003eguests_lock which is the correct way to protect against concurrent mdev_list access.  Also removed the following two lines of code because the matrix_mdev is allocated via vfio_alloc_device macro which uses kzalloc, so req_trigger and cfg_chg_trigger are already zero-initialised when the struct is allocated before the call to vfio_register_emulated_iommu_dev. This prevents a window whereby these triggers are set to NULL after the device is exposed to userspace.  matrix_mdev-\u003ereq_trigger = NULL; matrix_mdev-\u003ecfg_chg_trigger = NULL;  vfio_ap_mdev_for_queue function ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The status_show function that supports display of the status attribute of the devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue function which iterates the matrix_dev-\u003emdev_list to find the object representing the queue device whose status is to be displayed. In order to traverse this list, the matrix_dev-\u003eguests_lock mutex must be held.  To fix this, the guests_lock mutex is taken prior to taking the matrix_dev-\u003emdevs_lock mutex in the status_show function. It is taken there rather than the vfio_ap_mdev_for_queue function - where it is needed - because it must be taken prior to the mdevs_lock mutex in order to adhere to the proper locking order and prevent a lockdep splat; also because the mdevs_lock is needed there to access fields within the matrix_mdev object in that function.  See the vfio-ap-locking.rst in the linux kernel tree.",
  "id": "DEBIAN-CVE-2026-89956",
  "modified": "2026-09-17T04:47:31.347390664Z",
  "published": "2026-09-16T11:17:05.920Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-89956"
    }
  ],
  "upstream": [
    "CVE-2026-89956"
  ]
}