IT40332: amqrmppa generates FDC XC006001 from xcsFreeMemFn with error xecS_I_PRIVATE_MEMORY_ERROR and Comment "invalid head tag"

APAR status

• Closed as program error.

Error description

• When a channel session ends due to an error(e.g. tcp connection
  closed unexpectedly) the channel process amqrmppa
  generates the following FDC with ccxReceiveThreadCleanup in MQM
  Function Stack.
  
  Probe Id          :- XC006001
  Component         :- xcsFreeMemFn
  Program Name      :- amqrmppa
  Major Errorcode   :- xecS_I_PRIVATE_MEMORY_ERROR
  Probe Description :- AMQ6091I: An internal IBM MQ error has
  occurred.
  Arith1            :- 31140656 (0x1db2b30)
  Comment1          :- invalid head tag
  
  MQM Function Stack
  ccxResponder
  rrxResponder
  ccxReceiveThreadFn
  ccxReceiveThreadCleanup
  cciEndConv
  rriAsyncConvControl
  rriFreeSess
  ccxStageFree
  xcsFreeMemFn
  xcsFFST
  
  MQM Trace History
  ...
  -----} rriMQIServerCall rc=rrcE_SEND_FAILED
  ----} rriMQIServerReceive rc=rrcE_SEND_FAILED
  ---} rriServerAsyncRcv rc=rrcE_SEND_FAILED
  --} cciProcessAsyncRcv rc=rrcE_SEND_FAILED
  -} cciProcessUserData rc=rrcE_SEND_FAILED
  } cciProcessOne rc=rrcE_SEND_FAILED
  { ccxReceiveThreadCleanup
  ...
  ----} rriRollback rc=OK
  ----{ ccxStageFree
  -----{ xcsFreeMemFn
  Data: 0x00000000 0x020fa7d0
  ...
  ------{ xcsFFST
  
  Head
  0x20fa7c0   3F535047  73020203  A0000000  00000000
  ?SPGs...........
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users using MQ Client applications with SHARECONV = 1 with
  channel sessions on the queue manager ending unexpectedly due to
  an error(e.g. tcp connection closed unexpectedly due to network
  interruptions or by the client)
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  During cleanup processing whilst a client connection closes
  unexpectedly, a defect in MQ channel session pointer management
  caused double free(i.e. MQ was attempting to free a dangling
  pointer referencing that had already been freed) and the FDC was
  generated when MQ detected the double free condition.
  
  Previous similar APARs IT34004, IT36729 and IT39506 failed to
  identify the additional possible double freeing of a pointer in
  this code area.
  

Problem conclusion

• MQ channel code has been modified to prevent the double free
  condition when the channel does not end gracefully.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.1 LTS   9.1.0.15
  v9.2 LTS   9.2.0.10
  v9.3 LTS   9.3.0.5
  v9.x CD    9.3.3
  
  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

  IBM MQ BASE MP

• Fixed component ID

  5724H7271

Applicable component levels