Microsoft KB Archive/183073

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

Article ID: 183073

Article Last Modified on 10/28/2006

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APPLIES TO


 * Microsoft Exchange Server 5.5 Standard Edition

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This article was previously published under Q183073





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: kbbug kbfix KB183073

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