Bug#54477: Crash on IN / CASE with NULL arguments

Incorrect handling of NULL arguments could lead to a crash on
the IN or CASE operations when either NULL arguments were
passed explicitly as arguments (IN) or implicitly generated by
the WITH ROLLUP modifier (both IN and CASE).

Item_func_case::find_item() assumed all necessary comparators
to be instantiated in fix_length_and_dec(). However, in the
presence of WITH ROLLUP modifier, arguments could be
substituted with an Item_null leading to an "unexpected"
STRING_RESULT comparator being invoked.

In addition to the problem identical to the above,
Item_func_in::val_int() could crash even with explicitly passed
NULL arguments due to an optimization in fix_length_and_dec()
leading to NULL arguments being ignored during comparators
creation.

mysql-test/r/func_in.result

@@ -750,4 +750,24 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 DROP TABLE t1;
 #
+# Bug#54477: Crash on IN / CASE with NULL arguments
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1), (2);
+SELECT 1 IN (NULL, a) FROM t1;
+1 IN (NULL, a)
+1
+NULL
+SELECT a IN (a, a) FROM t1 GROUP BY a WITH ROLLUP;
+a IN (a, a)
+1
+1
+NULL
+SELECT CASE a WHEN a THEN a END FROM t1 GROUP BY a WITH ROLLUP;
+CASE a WHEN a THEN a END
+1
+2
+NULL
+DROP TABLE t1;
+#
 End of 5.1 tests

mysql-test/t/func_in.test

@@ -539,6 +539,21 @@ EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL, NULL);
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#54477: Crash on IN / CASE with NULL arguments
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1), (2);
+
+SELECT 1 IN (NULL, a) FROM t1;
+
+SELECT a IN (a, a) FROM t1 GROUP BY a WITH ROLLUP;
+
+SELECT CASE a WHEN a THEN a END FROM t1 GROUP BY a WITH ROLLUP;
+
+DROP TABLE t1;
+
 --echo #
 
 --echo End of 5.1 tests

sql/item_cmpfunc.cc

@@ -2773,6 +2773,8 @@ Item *Item_func_case::find_item(String *str)
     /* Compare every WHEN argument with it and return the first match */
     for (uint i=0 ; i < ncases ; i+=2)
     {
+      if (args[i]->real_item()->type() == NULL_ITEM)
+        continue;
       cmp_type= item_cmp_type(left_result_type, args[i]->result_type());
       DBUG_ASSERT(cmp_type != ROW_RESULT);
       DBUG_ASSERT(cmp_items[(uint)cmp_type]);
@@ -4002,9 +4004,17 @@ longlong Item_func_in::val_int()
     return (longlong) (!null_value && tmp != negated);
   }
 
+  if ((null_value= args[0]->real_item()->type() == NULL_ITEM))
+    return 0;
+
   have_null= 0;
   for (uint i= 1 ; i < arg_count ; i++)
   {
+    if (args[i]->real_item()->type() == NULL_ITEM)
+    {
+      have_null= TRUE;
+      continue;
+    }
     Item_result cmp_type= item_cmp_type(left_result_type, args[i]->result_type());
     in_item= cmp_items[(uint)cmp_type];
     DBUG_ASSERT(in_item);