From 68a66d149a8c78ec6720f268597302883e48e9fa Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Sat, 19 Aug 2017 15:37:07 +0300 Subject: [PATCH] net_sched: fix order of queue length updates in qdisc_replace() This important to call qdisc_tree_reduce_backlog() after changing queue length. Parent qdisc should deactivate class in ->qlen_notify() called from qdisc_tree_reduce_backlog() but this happens only if qdisc->q.qlen in zero. Missed class deactivations leads to crashes/warnings at picking packets from empty qdisc and corrupting state at reactivating this class in future. Signed-off-by: Konstantin Khlebnikov Fixes: 86a7996cc8a0 ("net_sched: introduce qdisc_replace() helper") Acked-by: Cong Wang Signed-off-by: David S. Miller --- include/net/sch_generic.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 1c123e2b2415..67f815e5d525 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -806,8 +806,11 @@ static inline struct Qdisc *qdisc_replace(struct Qdisc *sch, struct Qdisc *new, old = *pold; *pold = new; if (old != NULL) { - qdisc_tree_reduce_backlog(old, old->q.qlen, old->qstats.backlog); + unsigned int qlen = old->q.qlen; + unsigned int backlog = old->qstats.backlog; + qdisc_reset(old); + qdisc_tree_reduce_backlog(old, qlen, backlog); } sch_tree_unlock(sch);