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Q183073: XADM: Microsoft IS Generates AV in LOGON::IncrObjCount

Article: Q183073
Product(s): Microsoft Exchange
Version(s): 5.5
Operating System(s): 
Keyword(s): 
Last Modified: 05-APR-1999

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 
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SYMPTOMS
========

Under heavy load, the Microsoft Information Store can generate an access
violation in LOGON::IncrObjCount if the server runs out of available memory.

CAUSE
=====

Two things coincide to cause this:

1. The server must run out of memory so that an attempt to allocate new memory
  fails.

2. The information store attempts an insert into an array (m_rgHsotVmsg) and
  realizes the available bytes in the array are allocated and attempts to
  allocate more memory for the array using PvRealloc.

The problem:
A check is made to see whether the pHsotT is null. If not, the information store
assumes it should allocate more memory and store it in a member variable. If the
PvRealloc fails, the original pointer is not destroyed unless the size passed in
is 0. This causes a problem because the store checks to see whether the
_original_ pointer is NULL, and, if not, goes ahead and attempts to insert a
member at the out-of-bounds index.

The call stack appears similar to the following:

> kb
FramePtr  RetAddr   Param1   Param2   Param3   Function Name
20b8f980  0041c70e  00013d78 2d660006 00000000
STORE!LOGON::IncrObjCount+0x74
20b8f99c  0041c674  2d66a4e0 2d660006 270627a0
STORE!MDB::HsotInsertPunk+0x7a
20b8f9b4  00454514  20b8fa14 00000493 20b8faa4 STORE!UNK::EcAddToSOT+0x18
20b8f9dc  0046d47a  33e3ee48 20b8fa14 00000000 STORE!EcGetTableOp+0xc7
20b8fa1c  0040c50d  33981010 00013d79 1809f824 STORE!EcGetTable+0x116
00013d79  00000000  00000000 00000000 00000000 STORE!EcRpc+0x426

m_cHsotVmsg 0x00006800
m_cHsotVmsgAlloc 0x00006680


STATUS
======

Microsoft has confirmed this to be a problem in Exchange Server 5.5.


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.

======================================================================
Keywords          :  
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : 5.5
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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