PH42667: ABEND ABN=5C6-00E20001,U=XXXXXX ,C=MQ900.9XX.SMC -CSQSGSTG,M=CSQGFRCV,LOC=CSQSLD1 .CSQSVBK

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The 5C6-00E20001 abend occurred while processing a DISPLAY
  CONN() TYPE(HANDLE) command for a handle associated with a
  topic. Routine CSQMDCOH was attempting to obtain storage from a
  PHB to hold the topic string to be reported by the command. The
  size of the storage being requested was '7FFFF000'x bytes, and
  the abend was subsequently issued due to the large size of the
  storage request.
  
  The incorrect length of the topic string originated from
  pointer mhnd.pPubHndlB in the handle not pointing to a PubEntry
  structure. It instead pointed to string "UTF-8" padded with
  many binary zeroes. This resulted in attempts to reference a
  pointer in the PubEntry structure chaining into low core
  storage, which is where the incorrect length originated from.
  
  Analysis of the stack of the EB which was using the handle,
  showed that it was in the process of closing the handle in
  CSQMCLS2, and had recently freed the memory at mhnd.pPubHndlB
  back to the kqiTAB.hTopicSet free chain. It was then
  subsequently reused to hold the aforementioned string.
  
  The problem here is a timing window between DISPLAY CONN()
  TYPE(HANDLE) processing and the topic handle being closed.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 1 Modification 0, Release 2          *
  *                 Modification 0 and Release 3 Modification 0. *
  ****************************************************************
  * PROBLEM DESCRIPTION: When running a DIS CONN(*)              *
  *                      TYPE(HANDLE) command, it is possible    *
  *                      for a storage allocation error to       *
  *                      occur, resulting in a 5C6-00E20001      *
  *                      abend and a dump to be taken.           *
  ****************************************************************
  The code that obtains storage for the output of this command
  requests a quantity of storage based on a memory address
  that had been freed and repurposed. This means that the code
  can request an invalid amount of storage, causing an abend.
  

Problem conclusion

• The field that was responsible for the request for an excessive
  quantity of storage is now reset after it is freed. As a result,
  an abend no longer occurs when storage is requested.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UI90170 UI90171 UI90172

Modules/Macros

• CSQMCLS2 CSQMDCOH CSQSRVRA CSQWSDWA
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R100 PSY UI90172

     UP23/02/04 P F302

• R200 PSY UI90171

     UP23/02/04 P F302

• R300 PSY UI90170

     UP23/02/04 P F302

Fix is available

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