Bug #30587: mysql crashes when trying to group by TIME div NUMBER

When calculating the result length of an integer DIV function 
the number of decimals was used without checking the result type
first. Thus an uninitialized number of decimals was used for some 
types. This caused an excessive amount of memory to be allocated 
for the field's buffer and crashed the server.

 
Fixed by using the number of decimals only for data types that 
can have decimals and thus have valid decimals number.

mysql-test/r/func_math.result

@@ -322,4 +322,50 @@ mod(5, cast(-2 as unsigned))	mod(5, 18446744073709551614)	mod(5, -2)
 select pow(cast(-2 as unsigned), 5), pow(18446744073709551614, 5), pow(-2, 5);
 pow(cast(-2 as unsigned), 5)	pow(18446744073709551614, 5)	pow(-2, 5)
 2.1359870359209e+96	2.1359870359209e+96	-32
+CREATE TABLE t1 (a timestamp, b varchar(20), c bit(1));
+INSERT INTO t1 VALUES('1998-09-23', 'str1', 1), ('2003-03-25', 'str2', 0);
+SELECT a DIV 900 y FROM t1 GROUP BY y;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def				y	y	8	19	11	Y	32800	0	63
+y
+22201025555
+22255916666
+SELECT DISTINCT a DIV 900 y FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def				y	y	8	19	11	Y	32800	0	63
+y
+22201025555
+22255916666
+SELECT b DIV 900 y FROM t1 GROUP BY y;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def				y	y	8	20	1	Y	32768	0	63
+y
+0
+SELECT c DIV 900 y FROM t1 GROUP BY y;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def				y	y	3	1	1	Y	32800	0	63
+y
+0
+DROP TABLE t1;
+CREATE TABLE t1(a LONGBLOB);
+INSERT INTO t1 VALUES('1'),('2'),('3');
+SELECT DISTINCT (a DIV 254576881) FROM t1;
+(a DIV 254576881)
+0
+SELECT (a DIV 254576881) FROM t1 UNION ALL 
+SELECT (a DIV 254576881) FROM t1;
+(a DIV 254576881)
+0
+0
+0
+0
+0
+0
+DROP TABLE t1;
+CREATE TABLE t1(a SET('a','b','c'));
+INSERT INTO t1 VALUES ('a');
+SELECT a DIV 2 FROM t1 UNION SELECT a DIV 2 FROM t1;
+a DIV 2
+0
+DROP TABLE t1;
 End of 5.0 tests

mysql-test/t/func_math.test

@@ -205,4 +205,31 @@ select mod(cast(-2 as unsigned), 3), mod(18446744073709551614, 3), mod(-2, 3);
 select mod(5, cast(-2 as unsigned)), mod(5, 18446744073709551614), mod(5, -2);
 select pow(cast(-2 as unsigned), 5), pow(18446744073709551614, 5), pow(-2, 5);
 
+#
+# Bug #30587: mysql crashes when trying to group by TIME div NUMBER
+#
+
+CREATE TABLE t1 (a timestamp, b varchar(20), c bit(1));
+INSERT INTO t1 VALUES('1998-09-23', 'str1', 1), ('2003-03-25', 'str2', 0);
+--enable_metadata
+SELECT a DIV 900 y FROM t1 GROUP BY y;
+SELECT DISTINCT a DIV 900 y FROM t1;
+SELECT b DIV 900 y FROM t1 GROUP BY y;
+SELECT c DIV 900 y FROM t1 GROUP BY y;
+--disable_metadata
+DROP TABLE t1;
+
+CREATE TABLE t1(a LONGBLOB);
+INSERT INTO t1 VALUES('1'),('2'),('3');
+SELECT DISTINCT (a DIV 254576881) FROM t1;
+SELECT (a DIV 254576881) FROM t1 UNION ALL 
+  SELECT (a DIV 254576881) FROM t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(a SET('a','b','c'));
+INSERT INTO t1 VALUES ('a');
+SELECT a DIV 2 FROM t1 UNION SELECT a DIV 2 FROM t1;
+DROP TABLE t1;
+
+
 --echo End of 5.0 tests

sql/item_func.cc

@@ -1380,7 +1380,11 @@ longlong Item_func_int_div::val_int()
 
 void Item_func_int_div::fix_length_and_dec()
 {
-  max_length=args[0]->max_length - args[0]->decimals;
+  Item_result argtype= args[0]->result_type();
+  /* use precision ony for the data type it is applicable for and valid */
+  max_length=args[0]->max_length -
+    (argtype == DECIMAL_RESULT || argtype == INT_RESULT ?
+     args[0]->decimals : 0);
   maybe_null=1;
   unsigned_flag=args[0]->unsigned_flag | args[1]->unsigned_flag;
 }