Re: [PATCH v3] hw/s390x: Fix a possible crash with passed-through virtio devices

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 18.11.25 um 18:40 schrieb Thomas Huth:
> From: Thomas Huth <thuth@redhat.com>
> 
> Consider the following nested setup: An L1 host uses some virtio device
> (e.g. virtio-keyboard) for the L2 guest, and this L2 guest passes this
> device through to the L3 guest. Since the L3 guest sees a virtio device,
> it might send virtio notifications to the QEMU in L2 for that device.
> But since the QEMU in L2 defined this device as vfio-ccw, the function
> handle_virtio_ccw_notify() cannot handle this and crashes: It calls
> virtio_ccw_get_vdev() that casts sch->driver_data into a VirtioCcwDevice,
> but since "sch" belongs to a vfio-ccw device, that driver_data rather
> points to a CcwDevice instead. So as soon as QEMU tries to use some
> VirtioCcwDevice specific data from that device, we've lost.
> 
> We must not take virtio notifications for such devices. Thus fix the
> issue by adding a check to the handle_virtio_ccw_notify() handler to
> refuse all devices that are not our own virtio devices. Like in the
> other branches that detect wrong settings, we return -EINVAL from the
> function, which will later be placed in GPR2 to inform the guest about
> the error.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>

Certainly a good first step. If needed we can improve further in the future.