MDEV-10020 InnoDB NOT IN Query Crash When One Item Is NULL

The problem was that the loop in get_func_mm_tree()
accessed improperly initialized instances of String,
which resided in the bzero'ed part of the in_vector::base array.

Strings in in_vector::base are originally initialized
in Item_func_in::fix_length_and_dec(),
in in_vector::in_vector() using sql_calloc,
rather than using a String constructor, so their str_charset
members are originally equal to NULL.

Strings in in_vector::base are later initialized
to good values in Item_func_in::fix_length_and_dec(),
using array->set(), in this code:

      uint j=0;
      for (uint i=1 ; i < arg_count ; i++)
      {
        array->set(j,args[i]);
        if (!args[i]->null_value)                      // Skip NULL values
          j++;
        else
          have_null= 1;
      }
      if ((array->used_count= j))
        array->sort();

NULLs are not taken into account, so at the end
array->used_count can be smaller than array->count.

This patch fixes the loop in opt_range.cc, in get_func_mm_tree(),
to access only properly initialized elements in in_vector::base,
preventing access to its bzero'ed non-initialized tail.

mysql-test/r/func_in.result

@@ -812,3 +812,22 @@ EXECUTE s;
 1
 DROP TABLE t1;
 # End of 5.3 tests
+#
+# Start of 10.0 tests
+#
+#
+# MDEV-10020 InnoDB NOT IN Query Crash When One Item Is NULL
+#
+CREATE TABLE t1
+(
+a INT(11),
+b VARCHAR(10),
+KEY (b)
+);
+INSERT INTO t1 VALUES (1,'x'),(2,'y'),(3,'z');
+SELECT * FROM t1 WHERE b NOT IN (NULL, '', 'A');
+a	b
+DROP TABLE t1;
+#
+# End of 10.0 tests
+#

mysql-test/t/func_in.test

@@ -606,3 +606,24 @@ EXECUTE s;
 DROP TABLE t1;
 
 --echo # End of 5.3 tests
+
+--echo #
+--echo # Start of 10.0 tests
+--echo #
+
+--echo #
+--echo # MDEV-10020 InnoDB NOT IN Query Crash When One Item Is NULL
+--echo #
+CREATE TABLE t1
+(
+  a INT(11),
+  b VARCHAR(10),
+  KEY (b)
+);
+INSERT INTO t1 VALUES (1,'x'),(2,'y'),(3,'z');
+SELECT * FROM t1 WHERE b NOT IN (NULL, '', 'A');
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.0 tests
+--echo #

sql/opt_range.cc

@@ -7730,7 +7730,7 @@ static SEL_TREE *get_func_mm_tree(RANGE_OPT_PARAM *param, Item_func *cond_func,
           break;
         }
         SEL_TREE *tree2;
-        for (; i < func->array->count; i++)
+        for (; i < func->array->used_count; i++)
         {
           if (func->array->compare_elems(i, i-1))
           {