CVE-2026-74515

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

KVM: s390: pci: Reject adapter interrupt forwarding if already enabled

The MPCIFC instruction doesn't allow registering adapter interrupts without first unregistering. So reject any request to enable interrupt forwarding if its already enabled for the zPCI device. This also fixes overwriting and thus leaking resources when the ioctl is called multiple times for the same device.