5.4-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang cong.wang@bytedance.com
[ Upstream commit 638ba5089324796c2ee49af10427459c2de35f71 ]
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 martin.ottens@fau.de Reported-by: Mingi Cho mincho@theori.io Signed-off-by: Cong Wang cong.wang@bytedance.com Link: https://patch.msgid.link/20250204005841.223511-4-xiyou.wangcong@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 73c952d482752..27bd18c74e858 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -739,9 +739,9 @@ 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; }