CVE-2024-26620

In the Linux kernel, the following vulnerability has been resolved:

s390/vfio-ap: always filter entire AP matrix

The vfio_ap_mdev_filter_matrix function is called whenever a new adapter or

domain is assigned to the mdev. The purpose of the function is to update

the guest's AP configuration by filtering the matrix of adapters and

domains assigned to the mdev. When an adapter or domain is assigned, only

the APQNs associated with the APID of the new adapter or APQI of the new

domain are inspected. If an APQN does not reference a queue device bound to

the vfio_ap device driver, then it's APID will be filtered from the mdev's

matrix when updating the guest's AP configuration.

Inspecting only the APID of the new adapter or APQI of the new domain will

result in passing AP queues through to a guest that are not bound to the

vfio_ap device driver under certain circumstances. Consider the following:

guest's AP configuration (all also assigned to the mdev's matrix):

14.0004

14.0005

14.0006

16.0004

16.0005

16.0006

unassign domain 4

unbind queue 16.0005

assign domain 4

When domain 4 is re-assigned, since only domain 4 will be inspected, the

APQNs that will be examined will be:

14.0004

16.0004

Since both of those APQNs reference queue devices that are bound to the

vfio_ap device driver, nothing will get filtered from the mdev's matrix

when updating the guest's AP configuration. Consequently, queue 16.0005

will get passed through despite not being bound to the driver. This

violates the linux device model requirement that a guest shall only be

given access to devices bound to the device driver facilitating their

pass-through.

To resolve this problem, every adapter and domain assigned to the mdev will

be inspected when filtering the mdev's matrix.