Article ID: 218178
Article Last Modified on 9/22/2005
APPLIES TO
- Microsoft SNA Server 3.0 Service Pack 4
- Microsoft SNA Server 4.0
This article was previously published under Q218178
SYMPTOMS
The SNA Server service (Snaservr.exe) may fail unexpectedly with an access violation in function snpugetc. This failure may occur when receiving an invalid formatted General Data Stream (GDS) variable from a mainframe. If Drwtsn32.exe is configured as the default debugger on the SNA Server system, the Drwtsn32.log file may contain an entry similar to the following when this access violation occurs:
Application error:
Application: exe\snaservr.dbg (pid=259)
11/26/1998 @ 8:56:47.484
Error: c0000005 (Access violation)
Function: snpugetc
0100a5ca 8d4e06 lea ecx,[esi+0x6]
ds:0120ea06=????????
0100a5cd 2bdd sub ebx,ebp
0100a5cf 0fbfef movsx ebp,di
0100a5d2 3beb cmp ebp,ebx
0100a5d4 7e27 jle snpugetc+0x4d (0100a5fd)
0100a5d6 85f6 test esi,esi
0100a5d8 7427 jz snpugetc+0x51 (0100a601)
0100a5da 668b00 mov ax,[eax]
ds:019dff01=????
0100a5dd 8b36 mov esi,[esi]
ds:00000000=????????
0100a5df 662b01 sub ax,[ecx]
ds:019d61f6=010c
Fault ->0100a5e2 0fbf5e04 movsx ebx,word ptr [esi+0x4]
ds:0120ea07=????
0100a5e6 0fbf6e06 movsx ebp,word ptr [esi+0x6]
ds:0120ea07=????
0100a5ea 8d7c07ff lea edi,[edi+eax-0x1]
ds:02bee908=????????
*----> Stack Back Trace <----*
FramePtr ReturnAd Param#1 Param#2 Param#3 Param#4 Function Name
0118fd2c 0105f212 019d257c a3160e06 002d042c 002d0360 snaservr!snpugetc
(FPO: [EBP 0xa3160e06] [2,0,4])
0118fd94 0105c297 002d0360 0000125d 0118fdf8 01144bdd snaservr!s1pxntur
(FPO: [EBP 0x002d042c] [3,19,4])
In addition, an event similar to the following will be logged in the Windows NT Application Event Log:
CAUSE
The access violation is caused when SNA Server receives a badly formatted GDS variable. In this case, the format of the Sign-On GDS variable 0x'1221' sent by the host was invalid.
This problem started to occur with SNA Server 3.0 with the introduction of SNA Server single sign on support, where SNA Server now explicitly parses the user and password data within the Sign-On GDS message.
RESOLUTION
SNA Server 4.0
To resolve this problem, obtain the latest service pack for SNA Server version 4.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack
SNA Server 3.0
To resolve this problem, obtain the latest service pack for SNA Server version 3.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
184307 How to Obtain the Latest SNA Server Version 3.0 Service Pack
STATUS
Microsoft has confirmed that this is a problem in SNA Server 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, SNA Server 4.0, 4.0 SP1, 4.0 SP2. This problem was first corrected in SNA Server version 3.0 Service Pack 4 and SNA Server version 4.0 Service Pack 3.
MORE INFORMATION
With Client message trace enabled, you may see output similar to the following:
PVI -----------------------------------------------
PVI 9A000001->010AF5B1 LU 6.2
PVI MSGID:SWAT MSGTYP:NTEOD Sense1:0000
PVI Sense2:0700
PVI
PVI ---- Header at address 014D4B00, 14 elements ----
PVI 0B010000 07000000 000E0000 01000301 <................>
PVI
PVI ---- Element at address 019D257C, start 13, end 268 ----
PVI 2A0502FF 0003D000 000406F3 F0F10019
PVI 10C4C5E5 C2C7F0F3 F14BC1D7 D7C3C3D3
PVI F207CE0B 1A0DF500 01002033 1221202F
PVI FF002201 40404040 40404040 E5F0F0F1
PVI F0F0F0F0 F0F0F0F0 D3D6C7C9 D5404040
PVI 40404040 40404040 40404040 40404040
PVI 40404040 40404040 D9C5C3C5 C9D9C5C3
PVI C5C9F0F0 F0F0F0F0 F0F0F0F0 40404040
PVI 40404040 40404040 40404040 40404040
PVI 40404040 40404040 40404040 40404040
PVI 40404040 40404040 40404040 40404040
PVI 40404040 40404040 40404040 40404040
PVI 40404040 40404040 40404040 40404040
PVI F0F0F0F0 F0F0F0F5 40404040 40404040
PVI 40404040 40404040 E4E2D9C9 C4404040
PVI 40404040 40404040 C3F0F0F0 F8F0D5D7
Decoding the data shows the following:
2033 1221 - Sign-on GDS variable of length 2033 (which is much too large).
202F FF00 - Sign-On Request Data of length 202F.
2201 - User ID subfield of length 22.
According to SNA Formats & Protocols, the user ID must be 1-10 bytes, so the only valid lengths are 3-12.
40404040 40404040 E5F0F0F1 F0F0F0F0 F0F0F0F0 D3D6C7C9 D5404040 40404040 - User ID
40404040 40404040 40404040 - This is supposed to be an 00,01 or 02 subfield, which it clearly isn't.
Therefore, the data within the above frame clearly shows incorrect SNA protocol.
Additional query words: SNA trap snpugetc
Keywords: kbbug kbfix kbsna300sp4fix kbsna400sp3fix kbqfe kbhotfixserver KB218178
