SNA Server/SnaBase Traps Receive Invalid Client Logon Message

ID: Q161777

The information in this article applies to:

Microsoft SNA Server, versions 2.0, 2.1, 2.11

SYMPTOMS

The SNA Server or SnaBase process will encounter an access violation (AV) when receiving a badly formatted client logon challenge message. This leads to the following problems:

Users with active sessions may find that their computers stop responding and eventually they lose their host sessions. New users will be unable to connect through SNA Server until the computer running SNA Server is restarted.

The following Windows NT application event log message occurs:

Event ID: 624
Source: SNA Server
Creating dump file C:\SNA\traces\snadump.log for SNASERVR.DBG

A Drwtsn32.log entry is created that indicates an application exception error occurred in Snaservr.dbg:


      Application exception occurred:
           App: snaservr.DBG (pid=<process ID>)  (or snabase.DBG)
           Exception number: c0000005 (access violation)

      State Dump for Thread Id <thread ID>

      eax=0000002a ebx=00000000 ecx=00000000 edx=00000000 esi=01213463
      edi=0000002a
      eip=00ab956b esp=4cd4fa14 ebp=62f5002a iopl=0         nv up ei pl nz
      na pe nc
      cs=001b  ss=0023  ds=0023  es=0023  fs=0038  gs=0000
      efl=00000202

      function: GetSecField
      [...]
      FAULT ->00ab956b 0fbf4206   movsx eax,word ptr [edx+0x6]
      ds:005de923=????

The SNA Server service must be restarted to recover. If an SnaBase failure occurs, both the SnaBase and SNA Server services must be restarted to recover.

CAUSE

The cause of the improperly formatted client logon challenge message is unknown. The person who experienced this problem was using SNA Server 2.1 Windows 3.x client computers with a third-party (Korean) TCP/IP protocol stack. SNA Server did not expect such an invalid message to be received from a client computer, causing the server to attempt to process the message without validating the format. This led to an SNA Server access violation.

RESOLUTION

To resolve this problem, obtain the hotfix mentioned below. This hotfix prevents the access violation from occurring. However, it does not correct the client-side problem. Microsoft recommends upgrading the SNA Server clients to the latest supported software level.

STATUS

Microsoft has confirmed this to be a problem in SNA Server versions 2.0, 2.1. and 2.11. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

Additional query words: prodsna 2.00 2.10 2.11

Keywords : snaserverservice
Version : WINDOWS:2.0,2.1,2.11
Platform : WINDOWS
Issue type :