CVE-2026-89960: Linux kernel · s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()
Source GCVE Database
Not known to be exploited · CVSS 8.8 High · fixed in fc069d00a0dbef40042fd681554d48dcd5a1d524 : patch Linux kernel soon.
Data as of 30 Oct 2026, 16:33 UTC
Thin evidence
One scorer or none| CNA (Linux) | CVSS 3.1 | 8.8 |
|---|
- Patch
- Available – fixed in fc069d00a0dbef40042fd681554d48dcd5a1d524, eb6cc898501a004c0fa8aab951351d9c959b91cc, d6b7b166d5310fa3e4d5802c4177a0264d9140bd +3
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
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| LinuxLinux | Affected
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| LinuxLinux | Affected
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| LinuxLinux | Affected
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| LinuxLinux | Affected
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| LinuxLinux | Affected
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| LinuxLinux | Affected
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Description
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.
References
- nvd.nist.gov/vuln/detail/CVE-2026-89960 (opens in a new tab)
- git.kernel.org/stable/c/13bfc94eef389bd664ffc67b00184919902c938a (opens in a new tab)
- git.kernel.org/stable/c/4400270ec0348d05dc0439d8f0130853ce7f9e20 (opens in a new tab)
- git.kernel.org/stable/c/6a180adafc2a8a5fbe815985c71b2201e93ab5e1 (opens in a new tab)
- git.kernel.org/stable/c/d6b7b166d5310fa3e4d5802c4177a0264d9140bd (opens in a new tab)
- git.kernel.org/stable/c/eb6cc898501a004c0fa8aab951351d9c959b91cc (opens in a new tab)
- git.kernel.org/stable/c/fc069d00a0dbef40042fd681554d48dcd5a1d524 (opens in a new tab)