Bug #19573096: LOADING CORRUPTED GEOMETRY DATA INTO A

               MYISAM TABLE CAUSES THE SERVER TO CRASH

Issue:
-----
During index maintanence, R-tree node might need a split.
In some cases the square of mbr could be calculated to
infinite (as in this case) or to NaN. This is currently
not handled. This is specific to MyISAM.

SOLUTION:
---------
If the calculated value in "mbr_join_square" is infinite or
NaN, set it to max double value.

Initialization of output parameters of "pick_seeds" is
required if calculation is infinite (or negative infinite).

Similar to the fix made for INNODB as part of Bug#19533996.

storage/myisam/rt_split.c

-/* Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2002, 2015, Oracle and/or its affiliates. All rights reserved.
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -68,6 +68,10 @@ static double mbr_join_square(const double *a, const double *b, int n_dim)
     b += 2;
   }while (a != end);
 
+   /* Check for infinity or NaN */
+  if (my_isinf(square) || isnan(square))
+    square = DBL_MAX;
+
   return square;
 }
 
@@ -102,6 +106,9 @@ static void pick_seeds(SplitStruct *node, int n_entries,
   double max_d = -DBL_MAX;
   double d;
 
+  *seed_a = node;
+  *seed_b = node + 1;
+
   for (cur1 = node; cur1 < lim1; ++cur1)
   {
     for (cur2=cur1 + 1; cur2 < lim2; ++cur2)