From 8d74cbe34830ecd9401ac0964640638d40cf7755 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Mon, 3 Feb 2025 16:58:40 -0800 Subject: [PATCH] netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() qdisc_tree_reduce_backlog() notifies parent qdisc only if child qdisc becomes empty, therefore we need to reduce the backlog of the child qdisc before calling it. Otherwise it would miss the opportunity to call cops->qlen_notify(), in the case of DRR, it resulted in UAF since DRR uses ->qlen_notify() to maintain its active list. Fixes: f8d4bc455047 ("net/sched: netem: account for backlog updates from child qdisc") Cc: Martin Ottens Reported-by: Mingi Cho Signed-off-by: Cong Wang Link: https://patch.msgid.link/20250204005841.223511-4-xiyou.wangcong@gmail.com Signed-off-by: Jakub Kicinski --- net/sched/sch_netem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 152dbbe8fd31..447d3e836a24 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -748,9 +748,9 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch) if (err != NET_XMIT_SUCCESS) { if (net_xmit_drop_count(err)) qdisc_qstats_drop(sch); - qdisc_tree_reduce_backlog(sch, 1, pkt_len); sch->qstats.backlog -= pkt_len; sch->q.qlen--; + qdisc_tree_reduce_backlog(sch, 1, pkt_len); } goto tfifo_dequeue; } -- Gitee