Bug #59241 invalid memory read in do_div_mod with doubly assigned variables

Fix: copy my_decimal by value, to avoid dangling pointers.

mysql-test/r/func_math.result

@@ -641,3 +641,12 @@ INSERT INTO t1 (SELECT -pi());
 Warnings:
 Warning	1265	Data truncated for column 'a' at row 1
 DROP TABLE t1;
+#
+# Bug #59241 invalid memory read
+#            in do_div_mod with doubly assigned variables
+#
+SELECT ((@a:=@b:=1.0) div (@b:=@a:=get_format(datetime, 'usa')));
+((@a:=@b:=1.0) div (@b:=@a:=get_format(datetime, 'usa')))
+NULL
+Warnings:
+Warning	1366	Incorrect decimal value: '' for column '' at row -1

mysql-test/t/func_math.test

@@ -489,3 +489,9 @@ as foo;
 CREATE TABLE t1(a char(0));
 INSERT INTO t1 (SELECT -pi());
 DROP TABLE t1;
+
+--echo #
+--echo # Bug #59241 invalid memory read
+--echo #            in do_div_mod with doubly assigned variables
+--echo #
+SELECT ((@a:=@b:=1.0) div (@b:=@a:=get_format(datetime, 'usa')));

sql/item_cmpfunc.cc

-/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -2086,7 +2086,6 @@ void Item_func_interval::fix_length_and_dec()
             if (dec != &range->dec)
             {
               range->dec= *dec;
-              range->dec.fix_buffer_pointer();
             }
           }
           else

sql/item_func.cc

-/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1581,24 +1581,22 @@ longlong Item_func_int_div::val_int()
   if (args[0]->result_type() != INT_RESULT ||
       args[1]->result_type() != INT_RESULT)
   {
-    my_decimal value0, value1, tmp;
-    my_decimal *val0, *val1;
-    longlong res;
-    int err;
-
-    val0= args[0]->val_decimal(&value0);
-    val1= args[1]->val_decimal(&value1);
+    my_decimal tmp;
+    my_decimal val0= *args[0]->val_decimal(&tmp);
+    my_decimal val1= *args[1]->val_decimal(&tmp);
     if ((null_value= (args[0]->null_value || args[1]->null_value)))
       return 0;
 
+    int err;
     if ((err= my_decimal_div(E_DEC_FATAL_ERROR & ~E_DEC_DIV_ZERO, &tmp,
-                             val0, val1, 0)) > 3)
+                             &val0, &val1, 0)) > 3)
     {
       if (err == E_DEC_DIV_ZERO)
         signal_divide_by_null();
       return 0;
     }
 
+    longlong res;
     if (my_decimal2int(E_DEC_FATAL_ERROR, &tmp, unsigned_flag, &res) &
         E_DEC_OVERFLOW)
       raise_integer_overflow();

sql/my_decimal.h

-/* Copyright (C) 2005-2006 MySQL AB
+/* Copyright (c) 2005, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -102,6 +102,24 @@ class my_decimal :public decimal_t
 
 public:
 
+  my_decimal(const my_decimal &rhs) : decimal_t(rhs)
+  {
+    for (uint i= 0; i < DECIMAL_BUFF_LENGTH; i++)
+      buffer[i]= rhs.buffer[i];
+    fix_buffer_pointer();
+  }
+
+  my_decimal& operator=(const my_decimal &rhs)
+  {
+    if (this == &rhs)
+      return *this;
+    decimal_t::operator=(rhs);
+    for (uint i= 0; i < DECIMAL_BUFF_LENGTH; i++)
+      buffer[i]= rhs.buffer[i];
+    fix_buffer_pointer();
+    return *this;
+  }
+
   void init()
   {
     len= DECIMAL_BUFF_LENGTH;
@@ -248,7 +266,6 @@ inline
 void my_decimal2decimal(const my_decimal *from, my_decimal *to)
 {
   *to= *from;
-  to->fix_buffer_pointer();
 }
 
 

sql/sql_analyse.cc

-/* Copyright (C) 2000-2006 MySQL AB
+/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -521,9 +521,6 @@ void field_decimal::add()
   {
     found = 1;
     min_arg = max_arg = sum[0] = *dec;
-    min_arg.fix_buffer_pointer();
-    max_arg.fix_buffer_pointer();
-    sum[0].fix_buffer_pointer();
     my_decimal_mul(E_DEC_FATAL_ERROR, sum_sqr, dec, dec);
     cur_sum= 0;
     min_length = max_length = length;
@@ -545,12 +542,10 @@ void field_decimal::add()
     if (my_decimal_cmp(dec, &min_arg) < 0)
     {
       min_arg= *dec;
-      min_arg.fix_buffer_pointer();
     }
     if (my_decimal_cmp(dec, &max_arg) > 0)
     {
       max_arg= *dec;
-      max_arg.fix_buffer_pointer();
     }
   }
 }

strings/decimal.c

-/* Copyright (C) 2000 MySQL AB
+/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -13,8 +13,6 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
-#line 18 "decimal.c"
-
 /*
 =======================================================================
   NOTE: this library implements SQL standard "exact numeric" type