Bug#25172: Not checked buffer size leads to a server crash.

After fix for bug#21798 JOIN stores the pointer to the buffer for sorting
fields. It is used while sorting for grouping and for ordering. If ORDER BY
clause has more elements then the GROUP BY clause then a memory overrun occurs.

Now the length of the ORDER BY list is always passed to the 
make_unireg_sortorder() function and it allocates buffer big enough to be
used for bigger list.

mysql-test/r/select.result

@@ -3611,3 +3611,11 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	range	si,ai	si	5	NULL	2	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY,ci	PRIMARY	4	test.t2.a	1	Using where
 DROP TABLE t1,t2,t3;
+CREATE TABLE t1 ( f1 int primary key, f2 int, f3 int, f4 int, f5 int, f6 int, checked_out int);
+CREATE TABLE t2 ( f11 int PRIMARY KEY );
+INSERT INTO t1 VALUES (1,1,1,0,0,0,0),(2,1,1,3,8,1,0),(3,1,1,4,12,1,0);
+INSERT INTO t2 VALUES (62);
+SELECT * FROM t1 LEFT JOIN t2 ON f11 = t1.checked_out GROUP BY f1 ORDER BY f2, f3, f4, f5 LIMIT 0, 1;
+f1	f2	f3	f4	f5	f6	checked_out	f11
+1	1	1	0	0	0	0	NULL
+DROP TABLE t1, t2;

mysql-test/t/select.test

@@ -3092,3 +3092,14 @@ SELECT t3.a FROM t1,t2,t3
         t3.c IN ('bb','ee');
 
 DROP TABLE t1,t2,t3;
+ 
+#
+# Bug#25172: Not checked buffer size leads to a server crash
+#
+CREATE TABLE t1 ( f1 int primary key, f2 int, f3 int, f4 int, f5 int, f6 int, checked_out int);
+CREATE TABLE t2 ( f11 int PRIMARY KEY );
+INSERT INTO t1 VALUES (1,1,1,0,0,0,0),(2,1,1,3,8,1,0),(3,1,1,4,12,1,0);
+INSERT INTO t2 VALUES (62);
+SELECT * FROM t1 LEFT JOIN t2 ON f11 = t1.checked_out GROUP BY f1 ORDER BY f2, f3, f4, f5 LIMIT 0, 1;
+DROP TABLE t1, t2;
+

sql/sql_delete.cc

@@ -142,7 +142,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
 
   if (order && order->elements)
   {
-    uint         length;
+    uint         length= 0;
     SORT_FIELD  *sortorder;
     TABLE_LIST   tables;
     List<Item>   fields;

sql/sql_select.cc

@@ -12262,7 +12262,7 @@ static int
 create_sort_index(THD *thd, JOIN *join, ORDER *order,
 		  ha_rows filesort_limit, ha_rows select_limit)
 {
-  uint length;
+  uint length= 0;
   ha_rows examined_rows;
   TABLE *table;
   SQL_SELECT *select;
@@ -12283,8 +12283,10 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
        !(join->select_options & SELECT_BIG_RESULT)) &&
       test_if_skip_sort_order(tab,order,select_limit,0))
     DBUG_RETURN(0);
+  for (ORDER *ord= join->order; ord; ord= ord->next)
+    length++;
   if (!(join->sortorder= 
-        make_unireg_sortorder(order,&length,join->sortorder)))
+        make_unireg_sortorder(order, &length, join->sortorder)))
     goto err;				/* purecov: inspected */
 
   table->sort.io_cache=(IO_CACHE*) my_malloc(sizeof(IO_CACHE),
@@ -12690,8 +12692,10 @@ SORT_FIELD *make_unireg_sortorder(ORDER *order, uint *length,
   for (ORDER *tmp = order; tmp; tmp=tmp->next)
     count++;
   if (!sortorder)
-    sortorder= (SORT_FIELD*) sql_alloc(sizeof(SORT_FIELD)*(count+1));
-  pos=sort=sortorder;
+    sortorder= (SORT_FIELD*) sql_alloc(sizeof(SORT_FIELD) *
+                                       (max(count, *length) + 1));
+  pos= sort= sortorder;
+
   if (!pos)
     return 0;
 

sql/sql_table.cc

@@ -3883,7 +3883,7 @@ copy_data_between_tables(TABLE *from,TABLE *to,
   Copy_field *copy,*copy_end;
   ulong found_count,delete_count;
   THD *thd= current_thd;
-  uint length;
+  uint length= 0;
   SORT_FIELD *sortorder;
   READ_RECORD info;
   TABLE_LIST   tables;

sql/sql_update.cc

@@ -304,7 +304,7 @@ int mysql_update(THD *thd,
 	Doing an ORDER BY;  Let filesort find and sort the rows we are going
 	to update
       */
-      uint         length;
+      uint         length= 0;
       SORT_FIELD  *sortorder;
       ha_rows examined_rows;