From: Eric Dumazet <edumazet@google.com>
Date: Thu, 14 May 2026 09:59:32 +0000 (+0000)
Subject: net/sched: sch_htb: do not change sch->flags in htb_dump()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b949fa69129e4b694ed11ee3be6d6edd4a9b8f4;p=thirdparty%2Flinux.git

net/sched: sch_htb: do not change sch->flags in htb_dump()

htb_dump() runs without holding qdisc spinlock.

It is illegal to touch sch->flags with non locked RMW,
as concurrent readers might see intermediate wrong values.

Set TCQ_F_OFFLOADED in control path (htb_init()) instead.

Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260514095935.3926276-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 1e600f65c8769..873337ac1cca2 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1147,6 +1147,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 	 * parts (especially calling ndo_setup_tc) on errors.
 	 */
 	q->offload = true;
+	sch->flags |= TCQ_F_OFFLOADED;
 
 	return 0;
 }
@@ -1207,11 +1208,6 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
 	struct nlattr *nest;
 	struct tc_htb_glob gopt;
 
-	if (q->offload)
-		sch->flags |= TCQ_F_OFFLOADED;
-	else
-		sch->flags &= ~TCQ_F_OFFLOADED;
-
 	sch->qstats.overlimits = q->overlimits;
 	/* Its safe to not acquire qdisc lock. As we hold RTNL,
 	 * no change can happen on the qdisc parameters.