qdisc: fix a module refcount leak in qdisc_create_dflt()

BugLink: https://bugs.launchpad.net/bugs/1878232

commit 166ee5b8 upstream.

Should qdisc_alloc() fail, we must release the module refcount
we got right before.

Fixes: 6da7c8fc ("qdisc: allow setting default queuing discipline")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/sched/sch_generic.c

@@ -626,18 +626,19 @@ struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
 	struct Qdisc *sch;
 
 	if (!try_module_get(ops->owner))
-		goto errout;
+		return NULL;
 
 	sch = qdisc_alloc(dev_queue, ops);
-	if (IS_ERR(sch))
-		goto errout;
+	if (IS_ERR(sch)) {
+		module_put(ops->owner);
+		return NULL;
+	}
 	sch->parent = parentid;
 
 	if (!ops->init || ops->init(sch, NULL) == 0)
 		return sch;
 
 	qdisc_destroy(sch);
-errout:
 	return NULL;
 }
 EXPORT_SYMBOL(qdisc_create_dflt);