Fix for bug #32559: connection hangs on query with name_const

Problem: passing a non-constant name to the NAME_CONST function results in a crash.

Fix: check the NAME_CONST name argument; return fake item type if we got
non-constant argument(s).


mysql-test/r/func_misc.result:
  Fix for bug #32559: connection hangs on query with name_const
    - test result.
mysql-test/t/func_misc.test:
  Fix for bug #32559: connection hangs on query with name_const
    - test case.
sql/item.cc:
  Fix for bug #32559: connection hangs on query with name_const
    - Item_name_const::type() now returns NULL_ITEM if non-constant arguments 
      were used to create the item to avoid wrong type casting.
sql/item.h:
  Fix for bug #32559: connection hangs on query with name_const
    - NAME_CONST name argument checked for invariability.

1 files changed, 11 insertions, 1 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 431d82af331..a75d0159848 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -1209,7 +1209,17 @@ bool Item_name_const::is_null()
 
 Item::Type Item_name_const::type() const
 {
-  return value_item->type();
+  /*
+    As 
+    1. one can try to create the Item_name_const passing non-constant 
+    arguments, although it's incorrect and 
+    2. the type() method can be called before the fix_fields() to get
+    type information for a further type cast, e.g. 
+    if (item->type() == FIELD_ITEM) 
+      ((Item_field *) item)->... 
+    we return NULL_ITEM in the case to avoid wrong casting.
+  */
+  return valid_args ? value_item->type() : NULL_ITEM;
 }