In the Linux kernel, the following vulnerability has been resolved: net/sched: schqfq: Fix null-deref in aggdequeue To prevent a potential crash in aggdequeue (net/sched/schqfq.c) when cl->qdisc->ops->peek(cl->qdisc) returns NULL, we check the return value before using it, similar to the existing approach in schhfsc.c. To avoid code duplication, the following changes are made: 1. Changed qdiscwarnnonwc(include/net/pktsched.h) into a static inline function. 2. Moved qdiscpeeklen from net/sched/schhfsc.c to include/net/pktsched.h so that schqfq can reuse it. 3. Applied qdiscpeeklen in aggdequeue to avoid crashing.