net: sched: ensure tc flower reoffload takes filter ref

Recent changes to TC flower remove the requirement for rtnl lock when
accessing and modifying filters. Refcounts now ensure access and deletion
do not happen concurrently. However, the reoffload function which cycles
through all filters and replays them to registered hw drivers is not
protected.

Use the fl_get_next_filter() function to cycle the filters for reoffload
and ensure the ref taken by this function is put when done with each
filter.
Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_flower.c

@@ -1683,41 +1683,41 @@ static void fl_walk(struct tcf_proto *tp, struct tcf_walker *arg,
 static int fl_reoffload(struct tcf_proto *tp, bool add, tc_setup_cb_t *cb,
 			void *cb_priv, struct netlink_ext_ack *extack)
 {
-	struct cls_fl_head *head = fl_head_dereference(tp);
 	struct tc_cls_flower_offload cls_flower = {};
 	struct tcf_block *block = tp->chain->block;
-	struct fl_flow_mask *mask;
+	unsigned long handle = 0;
 	struct cls_fl_filter *f;
 	int err;
 
-	list_for_each_entry(mask, &head->masks, list) {
-		list_for_each_entry(f, &mask->filters, list) {
+	while ((f = fl_get_next_filter(tp, &handle))) {
 		if (tc_skip_hw(f->flags))
-				continue;
+			goto next_flow;
 
 		cls_flower.rule =
 			flow_rule_alloc(tcf_exts_num_actions(&f->exts));
-			if (!cls_flower.rule)
+		if (!cls_flower.rule) {
+			__fl_put(f);
 			return -ENOMEM;
+		}
 
-			tc_cls_common_offload_init(&cls_flower.common, tp,
-						   f->flags, extack);
+		tc_cls_common_offload_init(&cls_flower.common, tp, f->flags,
+					   extack);
 		cls_flower.command = add ?
 			TC_CLSFLOWER_REPLACE : TC_CLSFLOWER_DESTROY;
 		cls_flower.cookie = (unsigned long)f;
-			cls_flower.rule->match.dissector = &mask->dissector;
-			cls_flower.rule->match.mask = &mask->key;
+		cls_flower.rule->match.dissector = &f->mask->dissector;
+		cls_flower.rule->match.mask = &f->mask->key;
 		cls_flower.rule->match.key = &f->mkey;
 
-			err = tc_setup_flow_action(&cls_flower.rule->action,
-						   &f->exts);
+		err = tc_setup_flow_action(&cls_flower.rule->action, &f->exts);
 		if (err) {
 			kfree(cls_flower.rule);
 			if (tc_skip_sw(f->flags)) {
 				NL_SET_ERR_MSG_MOD(extack, "Failed to setup flow action");
+				__fl_put(f);
 				return err;
 			}
-				continue;
+			goto next_flow;
 		}
 
 		cls_flower.classid = f->res.classid;
@@ -1726,16 +1726,20 @@ static int fl_reoffload(struct tcf_proto *tp, bool add, tc_setup_cb_t *cb,
 		kfree(cls_flower.rule);
 
 		if (err) {
-				if (add && tc_skip_sw(f->flags))
+			if (add && tc_skip_sw(f->flags)) {
+				__fl_put(f);
 				return err;
-				continue;
+			}
+			goto next_flow;
 		}
 
 		spin_lock(&tp->lock);
-			tc_cls_offload_cnt_update(block, &f->in_hw_count,
-						  &f->flags, add);
+		tc_cls_offload_cnt_update(block, &f->in_hw_count, &f->flags,
+					  add);
 		spin_unlock(&tp->lock);
-		}
+next_flow:
+		handle++;
+		__fl_put(f);
 	}
 
 	return 0;