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CVE-2026-89960

WysokieCVSS 8.8
Opublikowano: Zaktualizowano: Przetłumaczono: NVD NIST

Prawdopodobieństwo exploitacji (EPSS)

Niskie ryzyko
0.17%

Percentyl 6 - wyżej niż 6% wszystkich znanych CVE

Streszczenie

W jądrze Linux w funkcji vfio_ap_mdev_set_kvm() wskaźnik kvm->arch.crypto.pqap_hook jest ustawiany przed sprawdzeniem, czy inne urządzenie mdev nie jest już przypisane do tej samej instancji KVM. W przypadku błędu funkcja zwraca -EPERM bez przywrócenia wskaźnika, co prowadzi do pozostawienia nieaktualnego wskaźnika i potencjalnego use-after-free przy wykonaniu instrukcji PQAP przez gościa.

Ocena ryzyka

Podatność może prowadzić do użycia zwolnionej pamięci (use-after-free) w przestrzeni jądra, co w środowisku z maszynami wirtualnymi KVM na architekturze s390 może skutkować zawieszeniem systemu lub eskalacją uprawnień.

Rekomendacja

Zaktualizuj jądro Linux do wersji zawierającej poprawkę, która przenosi ustawianie pqap_hook_rwsem do get_update_locks_for_kvm() i prawidłowo zwalnia zasoby w przypadku błędu.

Inne podatności w Linux kernel

Zobacz wszystkie
Oryginalny opis (angielski, źródło NVD)

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.

Dane podatności pochodzą z NVD (NIST) · CISA KEV · EPSS