CVE-2026-89921

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

KVM: s390: Zero initialize data structures for inject_pfault_token

__kvm_inject_pfault_token() only sets .type and .u.ext.ext_params2 of
the on-stack struct kvm_s390_irq but the full ext substructure is copied
into the cpu local variable on inject. ext_params and pad contain stale
stack values.

Interrupt delivery only uses ext_params2, so nothing leaks to the guest,
but a host user can use the migration ioctls to get to the data.

Fix by zero-initializing the irq struct.
Do the same for the inti data structure.