From: Konstantin Khlebnikov Date: Sat, 19 Aug 2017 12:37:07 +0000 (+0300) Subject: net_sched: fix order of queue length updates in qdisc_replace() X-Git-Tag: v4.12.10~75 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8a4ae09809a7fea7e2505fc4cc89695c744cf12;p=thirdparty%2Fkernel%2Fstable.git net_sched: fix order of queue length updates in qdisc_replace() [ Upstream commit 68a66d149a8c78ec6720f268597302883e48e9fa ] 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 22e52093bfda7..db5b6b6346b36 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -785,8 +785,11 @@ 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);