Bug#21205695 DROP TABLE MAY CAUSE SLAVES TO BREAK

    Problem:
    ========
    1) Drop table queries are re-generated by server
    before writing the events(queries) into binlog
    for various reasons. If table name/db name contains
    a non regular characters (like latin characters),
    the generated query is wrong. Hence it breaks the
    replication.
    2) In the edge case, when table name/db name contains
    64 characters, server is throwing an assert
    assert(M_TBLLEN < 128)
    3) In the edge case, when db name contains 64 latin
    characters, binlog content is interpreted badly
    which is leading replication failure.

    Analysis & Fix :
    ================
    1) Parser reads the table name from the query and converts
    it to standard charset(utf8) and stores it in table_name variable.
    When drop table query is regenerated with the same table_name
    variable, it should be converted back to the original charset
    from standard charset(utf8).

    2) Latin character takes two bytes for each character. Limit
    of the identifier is 64. SYSTEM_CHARSET_MBMAXLEN is set to '3'.
    So there is a possiblity that tablename/dbname contains 3 * 64.
    Hence assert is changed to
    (M_TBLLEN <= NAME_CHAR_LEN*SYSTEM_CHARSET_MBMAXLEN)

    3) db_len in the binlog event header is taking 1 byte.
       db_len is ranged from 0 to 192 bytes (3 * 64).
       While reading the db_len from the event, server
       is casting to uint instead of uchar which is leading
       to bad db_len. This problem is fixed by changing the
       cast type to uchar.

1 files changed, 5 insertions, 5 deletions

diff --git a/sql/log_event.cc b/sql/log_event.cc
index 38efb2a9c6b..accb6a28dbd 100644
--- a/sql/log_event.cc
+++ b/sql/log_event.cc
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2015, 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
@@ -2792,7 +2792,7 @@ Query_log_event::Query_log_event(const char* buf, uint event_len,
   
   slave_proxy_id= thread_id = uint4korr(buf + Q_THREAD_ID_OFFSET);
   exec_time = uint4korr(buf + Q_EXEC_TIME_OFFSET);
-  db_len = (uint)buf[Q_DB_LEN_OFFSET]; // TODO: add a check of all *_len vars
+  db_len = (uchar)buf[Q_DB_LEN_OFFSET]; // TODO: add a check of all *_len vars
   error_code = uint2korr(buf + Q_ERR_CODE_OFFSET);
 
   /*
@@ -8960,9 +8960,9 @@ bool Table_map_log_event::write_data_body(IO_CACHE *file)
 {
   DBUG_ASSERT(m_dbnam != NULL);
   DBUG_ASSERT(m_tblnam != NULL);
-  /* We use only one byte per length for storage in event: */
-  DBUG_ASSERT(m_dblen < 128);
-  DBUG_ASSERT(m_tbllen < 128);
+
+  DBUG_ASSERT(m_dblen <= NAME_LEN);
+  DBUG_ASSERT(m_tbllen <= NAME_LEN);
 
   uchar const dbuf[]= { (uchar) m_dblen };
   uchar const tbuf[]= { (uchar) m_tbllen };