[SRU][J][PATCH 1/6] sch_htb: make htb_qlen_notify() idempotent

[Ian Whitfield]

From: Cong Wang <xiyou.wangcong at gmail.com>

htb_qlen_notify() always deactivates the HTB class and in fact could
trigger a warning if it is already deactivated. Therefore, it is not
idempotent and not friendly to its callers, like fq_codel_dequeue().

Let's make it idempotent to ease qdisc_tree_reduce_backlog() callers'
life.

Reported-by: Gerrard Tai <gerrard.tai at starlabs.sg>
Signed-off-by: Cong Wang <xiyou.wangcong at gmail.com>
Reviewed-by: Simon Horman <horms at kernel.org>
Link: https://patch.msgid.link/20250403211033.166059-2-xiyou.wangcong@gmail.com
Acked-by: Jamal Hadi Salim <jhs at mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni at redhat.com>
(cherry picked from commit 5ba8b837b522d7051ef81bacf3d95383ff8edce5)
CVE-2025-37798
Signed-off-by: Ian Whitfield <ian.whitfield at canonical.com>
---
 net/sched/sch_htb.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 8ce999e4ca32..f3a20a5ee306 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1504,6 +1504,8 @@ static void htb_qlen_notify(struct Qdisc *sch, unsigned long arg)
 {
 	struct htb_class *cl = (struct htb_class *)arg;
 
+	if (!cl->prio_activity)
+		return;
 	htb_deactivate(qdisc_priv(sch), cl);
 }
 
-- 
2.43.0