CVE-2021-46968

In the Linux kernel, the following vulnerability has been resolved:
s390/zcrypt: fix zcard and zqueue hot-unplug memleak Tests with kvm and a
kmemdebug kernel showed, that on hot unplug the zcard and zqueue structs
for the unplugged card or queue are not properly freed because of a
mismatch with get/put for the embedded kref counter. This fix now adjusts
the handling of the kref counters. With init the kref counter starts with

1. This initial value needs to drop to zero with the unregister of the card
   or queue to trigger the release and free the object.