CVE-2026-89960: Software Security Vulnerability Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gfv9-x355-hv69",
  "modified" : "2026-09-16T15:31:03Z",
  "published" : "2026-09-16T12:30:43Z",
  "aliases" : [ "CVE-2026-89960" ],
  "details" : "In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()\n\nIn vfio_ap_mdev_set_kvm(), kvm->arch.crypto.pqap_hook is set to\n&matrix_mdev->pqap_hook before the update locks are acquired and the\nmdev list is checked for a conflicting assignment. If another mdev is\nalready attached to the same KVM instance, the function returns -EPERM\nwithout restoring the hook pointer, leaving kvm->arch.crypto.pqap_hook\npointing at the failing matrix_mdev instead of the mdev that legitimately\nowns the KVM.\n\nSince matrix_mdev->kvm is never set on this error path,\nvfio_ap_mdev_unset_kvm() will not clean up the hook when matrix_mdev\nis later closed. If matrix_mdev is subsequently freed, any PQAP\ninstruction executed by the guest will dereference the stale pointer\nthrough pqap_hook_rwsem, resulting in a use-after-free.\n\nSince kvm->arch.crypto.pqap_hook is only set in the vfio_ap_mdev_set_kvm()\nfunction and is cleared in the vfio_ap_mdev_unset_kvm() function, a check\nfor 'kvm->arch.crypto.pqap_hook != NULL' is all that is needed to determine\nwhether it belongs to another mdev. This will alleviate the need to iterate\nthe matrix_dev->mdev_list list to see if the kvm object is assigned to\nanother mdev.This was introduced in v3 to alleviate the need to take the\nmdevs_lock while iterating the list; however, this did not prevent a\npotential race condition.\n\nThe pqap_hook_rwsem(write) is now performed inside\nget_update_locks_for_kvm(), which is updated to acquire\npqap_hook_rwsem(write) between kvm->lock and mdevs_lock. This ordering\nis consistent with the PQAP intercept path, which acquires pqap_hook_rwsem\nin read mode while srcu is held under vcpu->mutex, establishing the\ndependency: kvm->lock -> vcpu->mutex -> srcu -> pqap_hook_rwsem(read).\n\nThe pqap_hook_rwsem is now released inside the\nrelease_update_locks_for_kvm(), which is updated to release\npqap_hook_rwsem(write) between mdevs_lock and kvm->lock.\n\nAdditionally, kvm_put_kvm() in vfio_ap_mdev_unset_kvm() is moved\nafter release_update_locks_for_kvm(). Previously it was called while\nkvm->lock was held; if it were ever the last reference, kvm_destroy_vm()\nwould run under kvm->lock, which would deadlock.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-89960"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/13bfc94eef389bd664ffc67b00184919902c938a"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/4400270ec0348d05dc0439d8f0130853ce7f9e20"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/6a180adafc2a8a5fbe815985c71b2201e93ab5e1"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/eb6cc898501a004c0fa8aab951351d9c959b91cc"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/fc069d00a0dbef40042fd681554d48dcd5a1d524"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-09-16T11:17:06Z"
  }
}