net/mlx5_core: Fix soft lockup in steering error flow

In the error flow of adding flow rule to auto-grouped flow
table, we call to tree_remove_node.

tree_remove_node locks the node's parent, however the node's parent
is already locked by mlx5_add_flow_rule and this causes a deadlock.
After this patch, if we failed to add the flow rule, we unlock the
flow table before calling to tree_remove_node.

fixes: f0d22d187473 ('net/mlx5_core: Introduce flow steering autogrouped
flow table')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reported-by: Amir Vadai <amir@vadai.me>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/fs_core.c

@@ -1065,33 +1065,6 @@ unlock_fg:
 	return rule;
 }
 
-static struct mlx5_flow_rule *add_rule_to_auto_fg(struct mlx5_flow_table *ft,
-						  u8 match_criteria_enable,
-						  u32 *match_criteria,
-						  u32 *match_value,
-						  u8 action,
-						  u32 flow_tag,
-						  struct mlx5_flow_destination *dest)
-{
-	struct mlx5_flow_rule *rule;
-	struct mlx5_flow_group *g;
-
-	g = create_autogroup(ft, match_criteria_enable, match_criteria);
-	if (IS_ERR(g))
-		return (void *)g;
-
-	rule = add_rule_fg(g, match_value,
-			   action, flow_tag, dest);
-	if (IS_ERR(rule)) {
-		/* Remove assumes refcount > 0 and autogroup creates a group
-		 * with a refcount = 0.
-		 */
-		tree_get_node(&g->node);
-		tree_remove_node(&g->node);
-	}
-	return rule;
-}
-
 static struct mlx5_flow_rule *
 _mlx5_add_flow_rule(struct mlx5_flow_table *ft,
 		    u8 match_criteria_enable,
@@ -1119,8 +1092,23 @@ _mlx5_add_flow_rule(struct mlx5_flow_table *ft,
 				goto unlock;
 		}
 
-	rule = add_rule_to_auto_fg(ft, match_criteria_enable, match_criteria,
-				   match_value, action, flow_tag, dest);
+	g = create_autogroup(ft, match_criteria_enable, match_criteria);
+	if (IS_ERR(g)) {
+		rule = (void *)g;
+		goto unlock;
+	}
+
+	rule = add_rule_fg(g, match_value,
+			   action, flow_tag, dest);
+	if (IS_ERR(rule)) {
+		/* Remove assumes refcount > 0 and autogroup creates a group
+		 * with a refcount = 0.
+		 */
+		unlock_ref_node(&ft->node);
+		tree_get_node(&g->node);
+		tree_remove_node(&g->node);
+		return rule;
+	}
 unlock:
 	unlock_ref_node(&ft->node);
 	return rule;