org.apache.lucene.search.function.DocValues offers 3 public (optional) methods to access value statistics like min, max and average values of the internal values. A call to one of the methods will result in an infinite loop. The internal counter is not incremented.
I added a testcase, javadoc and a slightly different implementation to it. I guess this is not breaking any back compat. as a call to those methodes would have caused an infinite loop anyway.
I changed the return value of all of those methods to Float.NaN if the DocValues implementation does not contain any values.
It might be considerable to fix this in 2.4.2 and 2.3.3