KVM: Validate hva in kvm_gpc_activate_hva() to fix __kvm_gpc_refresh() WARN

KVM: Validate hva in kvm_gpc_activate_hva() to fix __kvm_gpc_refresh() WARN

Check that the virtual address is "ok" when activating a gfn_to_pfn_cache
with a host VA to ensure that KVM never attempts to use a bad address.

This fixes a bug where KVM fails to check the incoming address when
handling KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA in kvm_xen_vcpu_set_attr().

Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=fd555292a1da3180fc82
Tested-by: [email protected]
Signed-off-by: Pei Li <[email protected]>
Reviewed-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[sean: rewrite changelog with --verbose]
Signed-off-by: Sean Christopherson <[email protected]>