MySQL Bugs: #53699: MySQL gives wrong error when the arg COM_FIELD

Bug #53699	MySQL gives wrong error when the arg COM_FIELD_LIST's ist too long
Submitted:	17 May 2010 12:20	Modified:	4 May 2015 12:31
Reporter:	Andrey Hristov	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Errors	Severity:	S2 (Serious)
Version:	5.1.48	OS:	Any
Assigned to:	Assigned Account	CPU Architecture:	Any

Description:
The fix for the crashing COM_FIELD_LIST (Bug #53237), which will appear in 5.1.48 treats too much data (>NAME_LEN) for COM_FIELD_LIST) by returning an error message. The problem is that the error message is wrong and confusing.

    if (arg_length >= packet_length || arg_length > NAME_LEN)
    {
      my_message(ER_UNKNOWN_COM_ERROR, ER(ER_UNKNOWN_COM_ERROR), MYF(0));
      break;
    }

The error is wrong, because we know the command is COM_FIELD_LIST is being executed and it exists. If correct data is given to the server it won't give back to the user ER_UNKNOWN_COM_ERROR. Possible error code is ER_WRONG_TABLE_NAME.

How to repeat:
sql_parse.cc: 

   if (arg_length >= packet_length || arg_length > NAME_LEN)
    {
      my_message(ER_UNKNOWN_COM_ERROR, ER(ER_UNKNOWN_COM_ERROR), MYF(0));
      break;
    }

Suggested fix:
Change the error returned

Thank you for the bug report.

Posted by developer:
 
Bug was fixed in the WL#7126.

The error message and the length check that was previously made in sql_parse.cc were moved to parse_packet method in protocol_classic.cc:938:

if (len >= packet_length || len > NAME_LEN)
      goto malformed;
...

malformed:
  my_error(ER_MALFORMED_PACKET, MYF(0));

The error was changed to ER_MALFORMED_PACKET("Malformed communication packet.")

Noted in 5.7.8, 5.8.0 changelogs.

The error produced for a COM_FIELD_LIST command with too much data
was changed from ER_UNKNOWN_COM_ERROR to the more informative
ER_MALFORMED_PACKET.