---
id: CVE-2026-89960
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()

  In vfio_ap_mdev_set_kvm(), kvm->arch.crypto.pqap_hook is set to
  &matrix_mdev->pqap_hook be…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()

  In vfio_ap_mdev_set_kvm(), kvm->arch.crypto.pqap_hook is set to
  &matrix_mdev->pqap_hook be…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 86956e70761b3292156d668e87126844334dd71b <
    eb6cc898501a004c0fa8aab951351d9c959b91cc
  - >-
    Linux >= 86956e70761b3292156d668e87126844334dd71b <
    6a180adafc2a8a5fbe815985c71b2201e93ab5e1
  - >-
    Linux >= 86956e70761b3292156d668e87126844334dd71b <
    fc069d00a0dbef40042fd681554d48dcd5a1d524
  - >-
    Linux >= 86956e70761b3292156d668e87126844334dd71b <
    13bfc94eef389bd664ffc67b00184919902c938a
  - >-
    Linux >= 86956e70761b3292156d668e87126844334dd71b <
    4400270ec0348d05dc0439d8f0130853ce7f9e20
  - Linux 5.15
published: '2026-09-16'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T15:18:20.560'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89960'
references:
  - url: 'https://git.kernel.org/stable/c/13bfc94eef389bd664ffc67b00184919902c938a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4400270ec0348d05dc0439d8f0130853ce7f9e20'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6a180adafc2a8a5fbe815985c71b2201e93ab5e1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/eb6cc898501a004c0fa8aab951351d9c959b91cc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fc069d00a0dbef40042fd681554d48dcd5a1d524'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-16T10:53:53.959Z'
epss: 0.0017
epssPercentile: 0.05579
---

## Overview

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

s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()

In vfio_ap_mdev_set_kvm(), kvm->arch.crypto.pqap_hook is set to
&matrix_mdev->pqap_hook before the update locks are acquired and the
mdev list is checked for a conflicting assignment. If another mdev is
already attached to the same KVM instance, the function returns -EPERM
without restoring the hook pointer, leaving kvm->arch.crypto.pqap_hook
pointing at the failing matrix_mdev instead of the mdev that legitimately
owns the KVM.

Since matrix_mdev->kvm is never set on this error path,
vfio_ap_mdev_unset_kvm() will not clean up the hook when matrix_mdev
is later closed. If matrix_mdev is subsequently freed, any PQAP
instruction executed by the guest will dereference the stale pointer
through pqap_hook_rwsem, resulting in a use-after-free.

Since kvm->arch.crypto.pqap_hook is only set in the vfio_ap_mdev_set_kvm()
function and is cleared in the vfio_ap_mdev_unset_kvm() function, a check
for 'kvm->arch.crypto.pqap_hook != NULL' is all that is needed to determine
whether it belongs to another mdev. This will alleviate the need to iterate
the matrix_dev->mdev_list list to see if the kvm object is assigned to
another mdev.This was introduced in v3 to alleviate the need to take the
mdevs_lock while iterating the list; however, this did not prevent a
potential race condition.

The pqap_hook_rwsem(write) is now performed inside
get_update_locks_for_kvm(), which is updated to acquire
pqap_hook_rwsem(write) between kvm->lock and mdevs_lock. This ordering
is consistent with the PQAP intercept path, which acquires pqap_hook_rwsem
in read mode while srcu is held under vcpu->mutex, establishing the
dependency: kvm->lock -> vcpu->mutex -> srcu -> pqap_hook_rwsem(read).

The pqap_hook_rwsem is now released inside the
release_update_locks_for_kvm(), which is updated to release
pqap_hook_rwsem(write) between mdevs_lock and kvm->lock.

Additionally, kvm_put_kvm() in vfio_ap_mdev_unset_kvm() is moved
after release_update_locks_for_kvm(). Previously it was called while
kvm->lock was held; if it were ever the last reference, kvm_destroy_vm()
would run under kvm->lock, which would deadlock.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.