IT45113: SIGSEGV in reconnectable MQ client application

APAR status

• Closed as program error.

Error description

• An MQ client application crashes and dumps core (if enabled by
  the system) when attempting to use MQ client reconnection
  functionality.
  
  The following information (or similar) would be seen in the FDC
  file that is written by the MQ code running in the application.
  
  Here is an example from a MQ 9.3 client:
  Probe Id          :- XC130003
  Component         :- xehExceptionHandler
  Thread            :- 23    RemoteReconnect
  Arith1            :- 11 (0xb)
  Comment1          :- SIGSEGV: address not mapped(0xfffffff0)
  
  O/S Call Stack for current thread
  /opt/mqm/lib/libmqe_r.so(+0x3cbfa1)[0x56c2ffa1]
  ...
  MQM Function Stack
  rcnReconnectThread
  rcnDoReconnec
  zutLookupIterate
  rcnRecreateHandle
  rcnUpdateConnReconnectFail
  rcnFreeConnReconnectFailObject
  xcsFreeMemFn
  xcsCheckMem
  xcsFFST
  
  For 9.2 clients, the rcnFreeConnReconnectFailObject will not
  appear in the FFST call stack, but the remaining call stack will
  be similar.
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  MQ Reconnectable Client applications using publish subscribe
  messaging running on unreliable networks
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  A small window exists where if a client's network connection
  fails again whilst recovering from a network failure, the MQ
  client library attempts to free resources that have not been
  allocated.
  

Problem conclusion

• Extra checks have been put in place to verify the memory is
  allocated before trying to free it.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.2 LTS   9.2.0.25
  v9.3 LTS   9.3.0.20
  v9.4 LTS   9.4.0.0
  
  The latest available maintenance can be obtained from
  'IBM MQ Recommended Fixes'
  https://www.ibm.com/support/pages/recommended-fixes-ibm-mq
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'IBM MQ
  Planned Maintenance Release Dates'
  https://ibm.biz/mqplannedmaintenance
  
  ---------------------------------------------------------------
  

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:

Fix information

• Fixed component name

  MQ BASE V9.3

• Fixed component ID

  5724H7291

Applicable component levels