Bug#36563773 MYSQL SERVER 8.3.0 GLOBAL-BUFFER-OVERFLOW AT 'DECIMAL_BIN_SIZE_INLINE'

Limit the scale used when computing averages of decimal numbers.

Simplified patch backported.

Change-Id: If32143ad7ed55f841e3973e78fa8e98cc245e775

Author: Tor Didriksen

sql/item_sum.cc

@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2023, Oracle and/or its affiliates.
+/* Copyright (c) 2000, 2024, Oracle and/or its affiliates.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License, version 2.0,
@@ -1728,7 +1728,7 @@ void Item_sum_avg::fix_length_and_dec()
                                                              decimals,
                                                              unsigned_flag);
     f_precision= min(precision+DECIMAL_LONGLONG_DIGITS, DECIMAL_MAX_PRECISION);
-    f_scale=  args[0]->decimals;
+    f_scale = min<uint>(args[0]->decimals, f_precision);
     dec_bin_size= my_decimal_get_binary_size(f_precision, f_scale);
   }
   else {