pkt_sched: gen_estimator: add a new lock

gen_kill_estimator() / gen_new_estimator() is not always called with
RTNL held.

net/netfilter/xt_RATEEST.c is one user of these API that do not hold
RTNL, so random corruptions can occur between "tc" and "iptables".

Add a new fine grained lock instead of trying to use RTNL in netfilter.

Signed-off-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/gen_estimator.c

···
 
 /* Protects against soft lockup during large deletion */
 static struct rb_root est_root = RB_ROOT;
+static DEFINE_SPINLOCK(est_tree_lock);
 
 static void est_timer(unsigned long arg)
 {
···
  *
  * Returns 0 on success or a negative error code.
  *
- * NOTE: Called under rtnl_mutex
  */
 int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
 		      struct gnet_stats_rate_est *rate_est,
···
 	est->last_packets = bstats->packets;
 	est->avpps = rate_est->pps<<10;
 
+	spin_lock(&est_tree_lock);
 	if (!elist[idx].timer.function) {
 		INIT_LIST_HEAD(&elist[idx].list);
 		setup_timer(&elist[idx].timer, est_timer, idx);
···
 
 	list_add_rcu(&est->list, &elist[idx].list);
 	gen_add_node(est);
+	spin_unlock(&est_tree_lock);
 
 	return 0;
 }
···
  *
  * Removes the rate estimator specified by &bstats and &rate_est.
  *
- * NOTE: Called under rtnl_mutex
  */
 void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
 			struct gnet_stats_rate_est *rate_est)
 {
 	struct gen_estimator *e;
 
+	spin_lock(&est_tree_lock);
 	while ((e = gen_find_node(bstats, rate_est))) {
 		rb_erase(&e->node, &est_root);
 
···
 		list_del_rcu(&e->list);
 		call_rcu(&e->e_rcu, __gen_kill_estimator);
 	}
+	spin_unlock(&est_tree_lock);
 }
 EXPORT_SYMBOL(gen_kill_estimator);
 
···
 bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
 			  const struct gnet_stats_rate_est *rate_est)
 {
+	bool res;
+
 	ASSERT_RTNL();
 
-	return gen_find_node(bstats, rate_est) != NULL;
+	spin_lock(&est_tree_lock);
+	res = gen_find_node(bstats, rate_est) != NULL;
+	spin_unlock(&est_tree_lock);
+
+	return res;
 }
 EXPORT_SYMBOL(gen_estimator_active);