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CVE-2026-89958

Niskie ryzyko· EPSS 11%
Opublikowano: Zaktualizowano: Przetłumaczono: NVD NIST

Prawdopodobieństwo exploitacji (EPSS)

Niskie ryzyko
0.21%

Percentyl 11 - wyżej niż 11% wszystkich znanych CVE

Streszczenie

W jądrze Linux w sterowniku s390/vfio-ap występuje podatność polegająca na braku sprawdzenia, czy wskaźnik matrix_mdev->kvm nie jest NULL przed pobraniem mutexa matrix_mdev->kvm->lock. Jeśli matrix_mdev->kvm nigdy nie został ustawiony, próba pobrania blokady powoduje dereferencję wskaźnika NULL. Poprawka dodaje sprawdzenie matrix_mdev->kvm == NULL przed pobraniem mutexa.

Ocena ryzyka

Dereferencja wskaźnika NULL w jądrze może doprowadzić do awarii systemu (panic jądra) lub zawieszenia maszyny, co stanowi ryzyko odmowy usługi (DoS). Problem dotyczy systemów z architekturą s390 korzystających z vfio-ap.

Rekomendacja

Zaktualizuj jądro Linux do wersji zawierającej poprawkę dla CVE-2026-89958. Jeśli aktualizacja nie jest możliwa, ogranicz dostęp do funkcji vfio-ap na systemach s390 do zaufanych użytkowników.

Inne podatności w Linux kernel

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Oryginalny opis (angielski, źródło NVD)

In the Linux kernel, the following vulnerability has been resolved: s390/vfio-ap: Fix dereference matrix_mdev->kvm without checking for NULL The ap_driver structure has two fields which are function pointers to callbacks: * .on_config_changed: called at the start of the AP bus scan function to notify the device driver that the host AP configuration has changed and the associated AP devices will be added or removed accordingly. This gives the implementor a chance to evaluate the configuration changes and respond to them before the associated devices are added or removed. * .on_scan_complete: Called at the end of the AP bus scan function to notify the device driver that the host AP configuration has changed and the AP devices have been added or removed accordingly. This gives the implementor the opportunity to respond to the changes after the associated devices are added or removed. These two callbacks are implemented in the vfio_ap device driver via the vfio_ap_on_cfg_changed and vfio_ap_on_scan_complete functions respectively. Within the call stack of these two callback functions the matrix_mdev->kvm->lock mutex is taken without checking whether matrix_mdev->kvm is NULL or not. If matrix_mdev->kvm has never been set, trying to take the lock will trigger a NULL pointer dereference. This patch adds checks for matrix_mdev->kvm == NULL before taking the matrix_mdev->kvm->lock mutex. Note that the matrix_mdev->kvm->lock mutex taken in the vfio_ap_mdev_hot_plug_config function is moved to the calling function along with the matrix_dev->mdevs_lock which is needed there to access the fields of the matrix_mdev. It makes little sense to make the change the check for matrix_mdev->kvm there before taking the kvm->lock mutex only to have to move it out via another patch, so it is done in this patch. It is important to make note of the following: 1. The matrix_dev->guests_lock is acquired at the start of both callback functions. This ensures that matrix_mdev will not be removed via the vfio_ap_mdev_remove function because it too takes matrix_dev_guests_lock before removing the object; so, matrix_mdev will be available for the duration of the callback functions. 2. The matrix_dev->mdevs_lock mutex must be taken in order to access fields within the matrix_mdev structure 3. matrix_mdev->kvm->lock mutex must be taken before the matrix_dev->mdevs_lock to prevent a lockdep splat. 4: The kvm->lock must be held while plugging the guest's AP configuration into its SIE state description via the vfio_ap_mdev_update_guest_apcb function. 5. The vfio_ap_mdev_update_guest_apcb checks matrix_mdev->kvm to verify it is not NULL before doing the hot plug of the guest's AP configuration.

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