There was possible stack overrun in an edge case which handles invalid body of
a SP in mysql.proc . That should be case when mysql.proc has been changed
manually. Though, due to bug 21513, it can be exploited without having access
to mysql.proc only being able to create a stored routine.


mysql-test/r/sp.result:
  update result
mysql-test/t/sp.test:
  add a test case for the bug
sql/sp.cc:
  Fix stack overrun. This happen mostly when mysql.proc is damaged, though
  it's possible due to another bug which creates invalid SP body in mysql.proc
  (leading quote from a label being cut) to create stack overrun even without
  having direct access to mysql.proc