Bug#38469 invalid memory read and/or crash with utf8 text field, stored procedure, uservar

A stored procedure involving substrings could crash the server on certain
platforms because of invalid memory reads.
          
During storing the new blob-field value, the cached value's address range
overlapped that of the new field value. This caused problems when the 
cached value storage was reallocated to provide access for a new 
characater set representation. The patch checks the address ranges, and if
they overlap, the new field value is copied to a new storage before it is
converted to the new character set.


mysql-test/r/sp.result:
  Added result set
mysql-test/t/sp.test:
  Added test case
sql/field.cc:
  The source and destination address ranges of a character conversion must not overlap or the 'from' address will be invalidated as the temporary value-
  object is re-allocated to fit the new character set.
sql/field.h:
  Added comments

mysql-test/r/sp.result

@@ -6662,6 +6662,16 @@ drop procedure p1;
 drop function f1;
 drop view v1;
 drop table t1;
+drop procedure if exists `p2` $
+create procedure `p2`(in `a` text charset utf8)
+begin
+declare `pos` int default 1;
+declare `str` text charset utf8;
+set `str` := `a`;
+select substr(`str`, `pos`+ 1 ) into `str`;
+end $
+call `p2`('s s s s s s');
+drop procedure `p2`;
 # ------------------------------------------------------------------
 # -- End of 5.0 tests
 # ------------------------------------------------------------------

mysql-test/t/sp.test

@@ -7818,6 +7818,24 @@ drop function f1;
 drop view v1;
 drop table t1;
 
+#
+# Bug#38469 invalid memory read and/or crash with utf8 text field, stored procedure, uservar 
+#
+delimiter $;
+--disable_warnings
+drop procedure if exists `p2` $
+--enable_warnings
+create procedure `p2`(in `a` text charset utf8)
+begin
+        declare `pos` int default 1;
+        declare `str` text charset utf8;
+        set `str` := `a`;
+        select substr(`str`, `pos`+ 1 ) into `str`;
+end $
+delimiter ;$
+call `p2`('s s s s s s');
+drop procedure `p2`;
+
 --echo # ------------------------------------------------------------------
 --echo # -- End of 5.0 tests
 --echo # ------------------------------------------------------------------

sql/field.cc

@@ -6992,8 +6992,18 @@ int Field_blob::store(const char *from,uint length,CHARSET_INFO *cs)
     return 0;
   }
 
-  if (from == value.ptr())
+  /*
+    If the 'from' address is in the range of the temporary 'value'-
+    object we need to copy the content to a different location or it will be
+    invalidated when the 'value'-object is reallocated to make room for
+    the new character set.
+  */
+  if (from >= value.ptr() && from <= value.ptr()+value.length())
   {
+    /*
+      If content of the 'from'-address is cached in the 'value'-object
+      it is possible that the content needs a character conversion.
+    */
     uint32 dummy_offset;
     if (!String::needs_conversion(length, cs, field_charset, &dummy_offset))
     {

sql/field.h

@@ -1213,8 +1213,16 @@ public:
 
 class Field_blob :public Field_longstr {
 protected:
+  /**
+    The number of bytes used to represent the length of the blob.
+  */
   uint packlength;
-  String value;				// For temporaries
+  
+  /**
+    The 'value'-object is a cache fronting the storage engine.
+  */
+  String value;
+  
 public:
   Field_blob(char *ptr_arg, uchar *null_ptr_arg, uchar null_bit_arg,
 	     enum utype unireg_check_arg, const char *field_name_arg,