CVE-2026-23105: Undefined Security Weakness

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

net/sched: qfq: Use cl_is_active to determine whether class is active in qfq_rm_from_ag

This is more of a preventive patch to make the code more consistent and to prevent possible exploits that employ child qlen manipulations on qfq. use cl_is_active instead of relying on the child qdisc's qlen to determine class activation.