net: atm: reject out-of-range traffic classes in QoS validation

In the Linux kernel, the following vulnerability has been resolved: net: atm: reject out-of-range traffic classes in QoS validation Reject ATM traffic classes above ATM_ANYCLASS in check_tp(). SO_ATMQOS stores the supplied QoS after check_qos() succeeds, so accepting larger values leaves invalid traffic_class values in vcc->qos. That bad state later reaches pvc_info(), which indexes class_name[] with vcc->qos.{rx,tp}.traffic_class. Values above ATM_ANYCLASS cause an out-of-bounds read when /proc/net/atm/pvc is read. Tighten the existing QoS validation so invalid traffic_class values are rejected at the point where user supplied QoS is accepted.