kernel: use-after-free due to race condition occurring in dvb_ca_en50221.c

A race condition flaw leading to a use-after-free issue was found in the Linux kernel media subsystem in the DVB CA EN50221 interface of the DVB core device driver. It could occur in the dvbcaen50221release function if there is a disconnect after an open, because of the lack of a waitevent. A loc...