MySQL Bugs: #89850: Throwing exception if access to granted for table

Bug #89850	Throwing exception if access to granted for table
Submitted:	28 Feb 2018 14:54	Modified:	1 Apr 2018 7:25
Reporter:	Ekh KH	Email Updates:
Status:	No Feedback	Impact on me:	None
Category:	Connector / NET	Severity:	S2 (Serious)
Version:		OS:	Any
Assigned to:	Assigned Account	CPU Architecture:	Any
Tags:	bogus table access exception

Description:
Exception thrown after query when user does not have right for select from bogus_table.

How to repeat:
Just turn off user rights for select in mysql sever. 
Example of code :

            using (IDbConnection c = new MySqlConnection(value)) {
                List<PushMetaData> pmd = c.Query<PushMetaData>("select * from ios_push").ToList(); // here exception 
            }

Suggested fix:
Just replace function ClearKillFlag in datareader.cs with this code

    private void ClearKillFlag()
    {
      // This query will silently crash because of the Kill call that happened before.
      string dummyStatement = "SELECT * FROM bogus_table LIMIT 0"; /* dummy query used to clear kill flag */
      MySqlCommand dummyCommand = new MySqlCommand(dummyStatement, _connection) {InternallyCreated = true};

      try
      {
        dummyCommand.ExecuteReader(); // ExecuteReader catches the exception and returns null, which is expected.
      }
      catch (MySqlException ex)
      {
        int[] errors = { (int)MySqlErrorCode.NoSuchTable, (int)MySqlErrorCode.TableAccessDenied};
        if (Array.IndexOf(errors, (int)ex.Number) < 0)
                    throw;
      }
    }

Hello Ekh,

Thank you for the bug report.
Could you please provide repeatable steps (exact steps/sample project, C/Net,MySQl version, full stack trace etc. - please make it as private if you prefer) to confirm this issue at our end?

Thanks,
Chiranjeevi.

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

This issue still needs to be fixed.

Here is an example to reproduce it:

	var query = "SELECT * FROM INFORMATION_SCHEMA.tables";

	using (var cmd = new MySqlCommand(query))
	{
		cmd.Connection = connection;
		cmd.CommandTimeout = 1800;
		int limit = 10;
		int count = 0;
		
		using (var reader = cmd.ExecuteReader())
		{
			
			if (reader.HasRows)
			{
				while (reader.Read() && count < limit)
				{
					Console.WriteLine(reader.GetString(0));
					count += 1;
				}
				
			}
			
			cmd.Cancel();
			
		}
		
	}

Here is the stack trace:
 at MySql.Data.MySqlClient.MySqlStream.ReadPacket()
   at MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& affectedRow, Int64& insertedId)
   at MySql.Data.MySqlClient.Driver.GetResult(Int32 statementId, Int32& affectedRows, Int64& insertedId)
   at MySql.Data.MySqlClient.Driver.NextResult(Int32 statementId, Boolean force)
   at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
   at MySql.Data.MySqlClient.MySqlDataReader.ClearKillFlag()
   at MySql.Data.MySqlClient.MySqlDataReader.Close()
   at MySql.Data.MySqlClient.MySqlDataReader.Dispose()
   at UserQuery
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

I got error code 1109 "Unknown table 'BOGUS_TABLE' in information_schema", not 1146 (MySqlErrorCode.NoSuchTable) like what is caught in the source code.