net/mlx5: DR, Fix potential race in dr_rule_create_rule_nic

Selecting builder should be protected by the lock to prevent the case
where a new rule sets a builder in the nic_matcher while the previous
rule is still using the nic_matcher.

Fixing this issue and cleaning the error flow.

Fixes: b9b81e1 ("net/mlx5: DR, For short chains of STEs, avoid allocating ste_arr dynamically")
Signed-off-by: Yevgeny Kliteynik <[email protected]>
Reviewed-by: Alex Vesker <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: kliteyn

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_rule.c

@@ -1138,12 +1138,14 @@ dr_rule_create_rule_nic(struct mlx5dr_rule *rule,
 			 rule->flow_source))
 		return 0;
 
+	mlx5dr_domain_nic_lock(nic_dmn);
+
 	ret = mlx5dr_matcher_select_builders(matcher,
 					     nic_matcher,
 					     dr_rule_get_ipv(&param->outer),
 					     dr_rule_get_ipv(&param->inner));
 	if (ret)
-		return ret;
+		goto err_unlock;
 
 	hw_ste_arr_is_opt = nic_matcher->num_of_builders <= DR_RULE_MAX_STES_OPTIMIZED;
 	if (likely(hw_ste_arr_is_opt)) {
@@ -1152,12 +1154,12 @@ dr_rule_create_rule_nic(struct mlx5dr_rule *rule,
 		hw_ste_arr = kzalloc((nic_matcher->num_of_builders + DR_ACTION_MAX_STES) *
 				     DR_STE_SIZE, GFP_KERNEL);
 
-		if (!hw_ste_arr)
-			return -ENOMEM;
+		if (!hw_ste_arr) {
+			ret = -ENOMEM;
+			goto err_unlock;
+		}
 	}
 
-	mlx5dr_domain_nic_lock(nic_dmn);
-
 	ret = mlx5dr_matcher_add_to_tbl_nic(dmn, nic_matcher);
 	if (ret)
 		goto free_hw_ste;
@@ -1223,7 +1225,10 @@ dr_rule_create_rule_nic(struct mlx5dr_rule *rule,
 
 	mlx5dr_domain_nic_unlock(nic_dmn);
 
-	goto out;
+	if (unlikely(!hw_ste_arr_is_opt))
+		kfree(hw_ste_arr);
+
+	return 0;
 
 free_rule:
 	dr_rule_clean_rule_members(rule, nic_rule);
@@ -1238,12 +1243,12 @@ dr_rule_create_rule_nic(struct mlx5dr_rule *rule,
 		mlx5dr_matcher_remove_from_tbl_nic(dmn, nic_matcher);
 
 free_hw_ste:
-	mlx5dr_domain_nic_unlock(nic_dmn);
-
-out:
-	if (unlikely(!hw_ste_arr_is_opt))
+	if (!hw_ste_arr_is_opt)
 		kfree(hw_ste_arr);
 
+err_unlock:
+	mlx5dr_domain_nic_unlock(nic_dmn);
+
 	return ret;
 }