net/sched: flower: Add lock protection when remove filter handle

As IDR can't protect itself from the concurrent modification, place
idr_remove() under the protection of tp->lock.

Fixes: 08a0063d ("net/sched: flower: Move filter handle initialization earlier")
Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20240220085928.9161-1-jianbol@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/sched/cls_flower.c

@@ -2460,8 +2460,11 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	}
 
 errout_idr:
-	if (!fold)
+	if (!fold) {
+		spin_lock(&tp->lock);
 		idr_remove(&head->handle_idr, fnew->handle);
+		spin_unlock(&tp->lock);
+	}
 	__fl_put(fnew);
 errout_tb:
 	kfree(tb);