Bug #55568: user variable assignments crash server when used

            within query

The server could crash after materializing a derived table
which requires a temporary table for grouping.

When destroying the temporary table used to execute a query for
a derived table, JOIN::destroy() did not clean up Item_fields
pointing to fields in the temporary table. This led to
dereferencing a dangling pointer when printing out the items
tree later in the outer SELECT.

The solution is an addendum to the patch for bug37362: in
addition to cleaning up items in tmp_all_fields3, do the same
for items in tmp_all_fields1, since now we have an example
where this is necessary.


mysql-test/r/join.result:
  Added test cases for bug#55568 and a duplicate bug #54468.
mysql-test/t/join.test:
  Added test cases for bug#55568 and a duplicate bug #54468.
sql/field.cc:
  Make sure field->table_name is not set to NULL in
  Field::make_field() to avoid assertion failure in 
  Item_field::make_field() after cleaning up items
  (the assertion fired in udf.test when running
  the test suite with the patch applied).
sql/sql_select.cc:
  In addition to cleaning up items in tmp_all_fields3, do the
  same for items in tmp_all_fields1.
  Introduce a new helper function to avoid code duplication.
sql/sql_select.h:
  Introduce a new helper function to avoid code duplication in
  JOIN::destroy().

1 files changed, 46 insertions, 0 deletions

diff --git a/mysql-test/t/join.test b/mysql-test/t/join.test
index 43b373c9703..6969be6fdc4 100644
--- a/mysql-test/t/join.test
+++ b/mysql-test/t/join.test
@@ -851,4 +851,50 @@ ENGINE=MERGE  UNION=(t1,t2);
 SELECT t1.a FROM mm1,t1;
 DROP TABLE t1, t2, mm1;
 
+--echo #
+--echo # Bug #55568: user variable assignments crash server when used within
+--echo #             query
+--echo #
+
+CREATE TABLE t1 (a INT);
+
+INSERT INTO t1 VALUES (0), (1);
+
+let $i=2;
+while ($i)
+{
+  SELECT MULTIPOINT(
+    1,
+    (
+      SELECT MULTIPOINT(
+        MULTIPOINT(
+          1,
+          (SELECT COUNT(*) FROM (SELECT 1 FROM t1 GROUP BY a,a) d)
+        )
+      ) FROM t1
+    )
+  ) != COUNT(*) q FROM t1 GROUP BY a;
+  dec $i;
+}
+
+DROP TABLE t1;
+
+--echo #
+--echo # Bug #54468: crash after item's print() function when ordering/grouping 
+--echo #             by subquery
+--echo #
+
+CREATE TABLE t1(a INT, b INT);
+INSERT INTO t1 VALUES (), ();
+
+SELECT 1 FROM t1
+GROUP BY
+GREATEST(t1.a,
+         (SELECT 1 FROM
+          (SELECT t1.b FROM t1,t1 t2
+           ORDER BY t1.a, t1.a LIMIT 1) AS d)
+        );
+
+DROP TABLE t1;
+
 --echo End of 5.1 tests