IT06884: MQ encounters SIGSEGV with probe ID XC130003 while deregistering a subscriber.

IBM MQ for HP NonStop Server V8.1 Fix Pack 8.1.0.5

APAR status

• Closed as program error.

Error description

• MQ reports SIGSEGV from kqiTopicDeregisterSubscriber while
  deregistering a subscriber.
  
  A failure data capture (FDC) record with probe id XC130003 is
  observed, with HALT6109 and SIGSEGV: address not mapped(0x2000).
  The call stack is as follows:
  
  O/S Call Stack for current thread
  /opt/mqm/mqxr/bin/../../lib64/libmqmcs_r.so(xcsPrintStackForCurr
  entThread+0x6e)[0x20085b6a2a6]
  /opt/mqm/mqxr/bin/../../lib64/libmqmcs_r.so(signalHandlerInterna
  l+0x50)[0x20085b8355c]
  /opt/mqm/mqxr/bin/../../lib64/libmqmcs_r.so(PrepareDumpAreas+0xc
  80)[0x20085b81ffc]
  /opt/mqm/mqxr/bin/../../lib64/libmqmcs_r.so(xcsFFSTFn+0x1124)[0x
  20085b85010]
  /opt/mqm/mqxr/bin/../../lib64/libmqmcs_r.so(xehExceptionHandler+
  0x27c)[0x20085b7f65c]
  [0x20095daf720]
  /opt/mqm/mqxr/bin/../../lib64/libmqml_r.so(kqiTopicDeregisterSub
  scriber+0x81a)[0x200865106da]
  /opt/mqm/mqxr/bin/../../lib64/libmqml_r.so(kqiCloseTopic+0xa8a)[
  0x200863fa58a]
  /opt/mqm/mqxr/bin/../../lib64/libmqml_r.so(kqiCloseIt+0x90c)[0x2
  0086335700]
  /opt/mqm/mqxr/bin/../../lib64/libmqml_r.so(kpiMQCLOSE+0x30e)[0x2
  0086336272]
  /opt/mqm/mqxr/bin/../../lib64/libmqml_r.so(zsqMQCLOSE+0x2f6)[0x2
  00864db872]
  /opt/mqm/lib64/amqzif_r(zifMQCLOSE+0x15a)[0x20084f3172a]
  /opt/mqm/mqxr/bin/../../lib64/libmqzi_r.so(zstMQCLOSE+0x61a)[0x2
  0086032e8a]
  /opt/mqm/lib64/libmqds_r.so(MQCLOSE+0xa2)[0x20084f0c542]
  /opt/mqm/mqxr/bin/../../lib64/libmqe_r.so(+0x432e60)[0x2008541de
  60]
  /opt/mqm/mqxr/bin/../../java/lib64/libmqjbnd.so(Java_com_ibm_mq_
  jmqi_local_internal_base_Native_MQCLOSE+0x176)[0x20084d488ae]
  
  MQM Function Stack
  MQCLOSE
  zstMQCLOSE
  zifMQCLOSE
  zsqMQCLOSE
  kpiMQCLOSE
  kqiCloseIt
  kqiCloseTopic
  kqiTopicDeregisterSubscriber
  xcsFFST
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users using WMQ 7.5 onwards with a publish/subscribe
  configuration where subscriptions are added/removed dynamically.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  A timing window existed within the publish/subscribe
  deregistration code, which could cause memory to be accessed
  after it had already been freed or reallocated. If encountered,
  this resulted in the SIGSEGV FDC from
  kqiTopicDeregisterSubscriber.
  

Problem conclusion

• Extra checking has been introduced while removing the topic link
  and subscription to avoid this illegal memory access.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v7.5       7.5.0.8
  v8.0       8.0.0.7
  v9.0 CD    9.0.2
  v9.0 LTS   9.0.0.1
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

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

  WMQ BASE MULTIP

• Fixed component ID

  5724H7241

Applicable component levels

• R750 PSY

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