A fix is available
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 number
PH42667
Reported component name
IBM MQ Z/OS V9
Reported component ID
5655MQ900
Reported release
100
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2021-12-08
Closed date
2023-01-20
Last modified date
2023-03-01
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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Document Information
Modified date:
01 March 2023