Is it okay to keep flour in the freezer?
Yes, of course you can keep flour in the freezer.  For whole wheat flour, which is susceptible to rancidity due to the fat from the whole grain being included, it is even recommended.

For white flour, according to the University of Nebraska Extension in Lancaster County (emphasis added):


  For longer storage, keep white flours in the refrigerator in an
  airtight container. All-purpose and bread flour will keep up to two
  years at 40 F in your refrigerator, according to the Wheat Foods
  Council. They can be stored indefinitely in the
  freezer.