From: Cong Wang Date: Tue, 4 Feb 2025 00:58:40 +0000 (-0800) Subject: netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() X-Git-Tag: v6.14-rc2~30^2~6^2~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=638ba5089324796c2ee49af10427459c2de35f71;p=thirdparty%2Fkernel%2Fstable.git 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 --- diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 71ec9986ed37f..fdd79d3ccd8ce 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -749,9 +749,9 @@ deliver: 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; }