mlx4_en: Fix out of bounds array access

When searching for a free entry in either mlx4_register_vlan() or
mlx4_register_mac(), and there is no free entry, the loop terminates without
updating the local variable free thus causing out of array bounds access. Fix
this by adding a proper check outside the loop.
Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mlx4/port.c

@@ -111,6 +111,12 @@ int mlx4_register_mac(struct mlx4_dev *dev, u8 port, u64 mac, int *index)
 			goto out;
 		}
 	}
+
+	if (free < 0) {
+		err = -ENOMEM;
+		goto out;
+	}
+
 	mlx4_dbg(dev, "Free MAC index is %d\n", free);
 
 	if (table->total == table->max) {
@@ -205,6 +211,11 @@ int mlx4_register_vlan(struct mlx4_dev *dev, u8 port, u16 vlan, int *index)
 		}
 	}
 
+	if (free < 0) {
+		err = -ENOMEM;
+		goto out;
+	}
+
 	if (table->total == table->max) {
 		/* No free vlan entries */
 		err = -ENOSPC;