CVE-2026-89958
Estado: RecibidaSin puntuar—
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:
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.
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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.
Detalles técnicos trazas, registros y código del informe original
* .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.
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.CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 4/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
- https://git.kernel.org/stable/c/178ea7a1c2c3c0c01d14b8f60aa35f1e0cdc6b78
- https://git.kernel.org/stable/c/334b435b951353f934d5110c4630e0cb58d2f9a7
- https://git.kernel.org/stable/c/4f7e869d0db24ae07b4c888fd3bc21554eef775d
- https://git.kernel.org/stable/c/5e932abfcce6189d067fffb0eb8214443bc04374
- https://git.kernel.org/stable/c/d50346801b4f144e42b49cd4f1496010498ab114
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-89958",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "eeb386aeb5b7c8d2dae6a3ba49255d8a97803182",
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"versionType": "git"
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{
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{
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{
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"versionType": "git"
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{
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"lessThan": "d50346801b4f144e42b49cd4f1496010498ab114",
"versionType": "git"
}
],
"programFiles": [
"drivers/s390/crypto/vfio_ap_ops.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.110",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.5",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/s390/crypto/vfio_ap_ops.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-16T11:17:06.177",
"references": [
{
"url": "https://git.kernel.org/stable/c/178ea7a1c2c3c0c01d14b8f60aa35f1e0cdc6b78",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/334b435b951353f934d5110c4630e0cb58d2f9a7",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
"url": "https://git.kernel.org/stable/c/5e932abfcce6189d067fffb0eb8214443bc04374",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d50346801b4f144e42b49cd4f1496010498ab114",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: Fix dereference matrix_mdev->kvm without checking for NULL\n\nThe ap_driver structure has two fields which are function pointers to\ncallbacks:\n\n* .on_config_changed: called at the start of the AP bus scan function to\n notify the device driver that the host AP\n configuration has changed and the associated AP\n devices will be added or removed accordingly. This\n gives the implementor a chance to evaluate the\n configuration changes and respond to them before\n the associated devices are added or removed.\n\n* .on_scan_complete: Called at the end of the AP bus scan function to\n notify the device driver that the host AP\n configuration has changed and the AP devices have\n been added or removed accordingly. This gives the\n implementor the opportunity to respond to the\n changes after the associated devices are added or\n removed.\n\nThese two callbacks are implemented in the vfio_ap device driver via the\nvfio_ap_on_cfg_changed and vfio_ap_on_scan_complete functions respectively.\n\nWithin the call stack of these two callback functions the\nmatrix_mdev->kvm->lock mutex is taken without checking whether\nmatrix_mdev->kvm is NULL or not. If matrix_mdev->kvm has never been set,\ntrying to take the lock will trigger a NULL pointer dereference. This patch\nadds checks for matrix_mdev->kvm == NULL before taking the\nmatrix_mdev->kvm->lock mutex.\n\nNote that the matrix_mdev->kvm->lock mutex taken in the\nvfio_ap_mdev_hot_plug_config function is moved to the calling function\nalong with the matrix_dev->mdevs_lock which is needed there to access\nthe fields of the matrix_mdev. It makes little sense to make the change\nthe check for matrix_mdev->kvm there before taking the kvm->lock\nmutex only to have to move it out via another patch, so it is done in\nthis patch.\n\nIt is important to make note of the following:\n1. The matrix_dev->guests_lock is acquired at the start of both callback\n functions. This ensures that matrix_mdev will not be removed via the\n vfio_ap_mdev_remove function because it too takes matrix_dev_guests_lock\n before removing the object; so, matrix_mdev will be available for the\n duration of the callback functions.\n\n2. The matrix_dev->mdevs_lock mutex must be taken in order to access\n fields within the matrix_mdev structure\n\n3. matrix_mdev->kvm->lock mutex must be taken before the\n matrix_dev->mdevs_lock to prevent a lockdep splat.\n\n4: The kvm->lock must be held while plugging the guest's AP configuration\n into its SIE state description via the vfio_ap_mdev_update_guest_apcb\n function.\n\n5. The vfio_ap_mdev_update_guest_apcb checks matrix_mdev->kvm to verify it\n is not NULL before doing the hot plug of the guest's AP configuration."
}
],
"lastModified": "2026-09-16T11:17:06.177",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}