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When QFQ has a CBS child which has a netem child it is possible to create a scenario where QFQ's qlen goes to 0 but the computation makes it underflow. This then aggrevates a null pointer deref. Jamal Hadi Salim (1): net/sched: sch_cbs: Call qdisc_reset for child qdisc Victor Nogueira (1): selftests/tc-testing: Add QFQ/CBS qlen underflow test net/sched/sch_cbs.c | 12 +++++- .../tc-testing/tc-tests/infra/qdiscs.json | 41 +++++++++++++++++++ 2 files changed, 52 insertions(+), 1 deletion(-) -- 2.34.1