bzr push into mysql-5.5-bugfixing branch (marc.alff:3209 to 3210) Bug#50557

[Marc Alff]

 3210 Marc Alff	2010-09-17
      Bug#50557 checksum table crashes server when used in performance_schema
      
      CHECKSUM TABLE for performance schema tables could cause uninitialized
      memory reads.
      
      The root cause is a design flaw in the implementation of
      mysql_checksum_table(), which do not honor null fields.
      
      However, fixing this bug in CHECKSUM TABLE is risky, as it can cause the
      checksum value to change.
      
      This fix implements a work around, to systematically reset fields values
      even for null fields, so that the field memory representation is always
      initialized with a known value.

    modified:
      storage/perfschema/pfs_engine_table.cc
 3209 Marc Alff	2010-09-17 [merge]
      local merge

    modified:
      sql/log.cc
      sql/log.h
      sql/sql_repl.cc
=== modified file 'storage/perfschema/pfs_engine_table.cc'
--- a/storage/perfschema/pfs_engine_table.cc	2010-08-12 14:08:52 +0000
+++ b/storage/perfschema/pfs_engine_table.cc	2010-09-17 19:03:09 +0000
@@ -223,6 +223,8 @@ int PFS_engine_table::read_row(TABLE *ta
                                Field **fields)
 {
   my_bitmap_map *org_bitmap;
+  Field *f;
+  Field **fields_reset;
 
   /*
     Make sure the table structure is as expected before mapping
@@ -240,6 +242,16 @@ int PFS_engine_table::read_row(TABLE *ta
 
   /* We internally write to Fields to support the read interface */
   org_bitmap= dbug_tmp_use_all_columns(table, table->write_set);
+
+  /*
+    Some callers of the storage engine interface do not honor the
+    f->is_null() flag, and will attempt to read the data itself.
+    A known offender is mysql_checksum_table().
+    For robustness, reset every field.
+  */
+  for (fields_reset= fields; (f= *fields_reset) ; fields_reset++)
+    f->reset();
+
   int result= read_row_values(table, buf, fields, read_all);
   dbug_tmp_restore_column_map(table->write_set, org_bitmap);
 


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