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.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index f051ed07a7e..ae5899d8de4 100644
--- a/sql/opt_range.cc
+++ b/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))
           {