Errors When Performance Monitoring SNA Server

• Microsoft SNA Server, versions 3.0 and 3.0 Service Pack 1 (SP1)

SYMPTOMS

When you initially activate Windows NT Server Performance Monitor to collect SNA Server performance data, the following errors may occur:

• Perfmon.exe may encounter an access violation.
• If SNA Server is running on Windows NT Server 3.51, a Winlogon.exe access violation may occur, leading to a STOP 0x0000001E error.
• If SNA Server is running on Windows NT Server 4.0, the following event may be logged in the Windows NT application event log:

        Event ID: 1013
        Source: Perflib
        Description:
        The collect procedure in Extensible Counter DLL
        "C:\SNA\system\snaperf.dll" for the "SnaServr" service returned a
        buffer that was larger than the space allocated and may have
        corrupted the application's heap. This DLL should be disabled or
        removed from the system until the problem has been corrected to
        prevent further corruption. The application accessing this
        performance data should be restarted. The Performance data returned
        by counter DLL will be not be returned in Perf Data Block. Overflow
        size is data DWORD 0.
  

• If SNA Server is running on Windows NT 4.0, a winlogon.exe access violation may occur, which would cause the following log entry in the <ntroot>\drwtsn32.log file:

        Application exception occurred:
        App: exe\winlogon.dbg (<process ID>)
        Exception number: c0000005 (access violation)
        [...]
        function: RtlAllocateHeap
        [...]
        FAULT ->77f64654 0fb716           movzx   edx,word ptr [esi]  
  
  
  

CAUSE

The SNA Server performance monitoring collection routine returns a Buffer Size greater than the Perfmon buffer pointer allocated. The data collection routines AddNodeCounters and AddRTMCounters write data to the buffer, but fail to decrement the remaining byte count, which results in the buffer write operation going past the end of the buffer.

STATUS

Microsoft has confirmed this to be a problem in SNA Server version 3.0 and 3.0 Service Pack 1. This problem was corrected in the latest SNA Server version 3.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

MORE INFORMATION

With the fix, the code has been modified to decrement the remaining byte count for the Node and RTM counter collections.