netdev - [PATCH net] sch_htb: Fix prematurely activating netdev during htb_destroy_class

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Message-Id: <20230104174744.22280-1-rrameshbabu@nvidia.com>
Date:   Wed,  4 Jan 2023 09:47:45 -0800
From:   Rahul Rameshbabu <rrameshbabu@...dia.com>
To:     netdev@...r.kernel.org
Cc:     Tariq Toukan <tariqt@...dia.com>, Gal Pressman <gal@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Rahul Rameshbabu <rrameshbabu@...dia.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Maxim Mikityanskiy <maxtram95@...il.com>
Subject: [PATCH net] sch_htb: Fix prematurely activating netdev during htb_destroy_class_offload

When the netdev qdisc is updated correctly with the new qdisc before
destroying the old qdisc, the netdev should not be activated till cleanup
is completed. When htb_destroy_class_offload called htb_graft_helper, the
netdev may be activated before cleanup is completed. The new netdev qdisc
may be used prematurely by queues before cleanup is done. Call
dev_graft_qdisc in place of htb_graft_helper when destroying the htb to
prevent premature netdev activation.

Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@...dia.com>
Acked-by: Saeed Mahameed <saeedm@...dia.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Maxim Mikityanskiy <maxtram95@...il.com>
---
 net/sched/sch_htb.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 2238edece1a4..f62334ef016a 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1557,14 +1557,16 @@ static int htb_destroy_class_offload(struct Qdisc *sch, struct htb_class *cl,
 
 	WARN_ON(!q);
 	dev_queue = htb_offload_get_queue(cl);
-	old = htb_graft_helper(dev_queue, NULL);
-	if (destroying)
+	if (destroying) {
+		old = dev_graft_qdisc(dev_queue, NULL);
 		/* Before HTB is destroyed, the kernel grafts noop_qdisc to
 		 * all queues.
 		 */
 		WARN_ON(!(old->flags & TCQ_F_BUILTIN));
-	else
+	} else {
+		old = htb_graft_helper(dev_queue, NULL);
 		WARN_ON(old != q);
+	}
 
 	if (cl->parent) {
 		_bstats_update(&cl->parent->bstats_bias,
-- 
2.36.2