---
cve: "CVE-2026-89960"
severity: "HIGH"
cvss: 8.8
epss: "0.2%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-09-16 11:17:06"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-20T20:05:49+02:00"
---

# CVE-2026-89960

> 8.8 HIGH

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Verändert | bad |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.6.157
- Kernel ≥ 6.12.110
- Kernel ≥ 6.18.51
- Kernel ≥ 7.2.5

## Referenzen

- <https://git.kernel.org/stable/c/eb6cc898501a004c0fa8aab951351d9c959b91cc>
- <https://git.kernel.org/stable/c/6a180adafc2a8a5fbe815985c71b2201e93ab5e1>
- <https://git.kernel.org/stable/c/fc069d00a0dbef40042fd681554d48dcd5a1d524>
- <https://git.kernel.org/stable/c/13bfc94eef389bd664ffc67b00184919902c938a>
- <https://git.kernel.org/stable/c/4400270ec0348d05dc0439d8f0130853ce7f9e20>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-89960) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_