OA57870: DECOMPRESSING A FILE WITH ZLIB SOFTWARE RESULTS IN INVALID OR INCOMPLETE DEFLATE DATA MESSAGE.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When unzipping a file that was compressed with zLib software
  functionality, the decompress fails with invalid or incomplete
  deflate data error message.
  
  An internal buffer overflows and data is incorrect when
  compressing. This buffer is small for compatibility with 16-bit
  machines.
  

Local fix

• BYPASS/CIRCUMVENTION:
  Changing the memlevel specified in deflateInit2 to max memlevel
  of 9 can prevent the internal buffer overflow for some files.
  
  deflateInit2(&strm, Z_DEFAULT_COMPRESSION
             ,Z_DEFLATED
             ,windowBits | GZIP_ENCODING
             ,9 --- max memlevel is 9
             ,Z_FIXED);
  
  This circumvention will not work for all files that are seeing
  the buffer overflow issue.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Any user of z/OS provied zlib                                *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * A few files that were compressed by                          *
  * software-based zLib generate                                 *
  * Z_DATA_ERROR while decompressing.                            *
  * This was caused by a buffer overflow                         *
  * during compression.                                          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  zLib generated corrupt compressed
  data because of internal buffer
  overflow.
  

Problem conclusion

• Enlarge zlib internal buffer so that
  data block won't cause overflow.
  

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:

  UJ00875 UJ00876 UJ00877

Modules/Macros

• HZCLIBSX HZCZLIB  HZCZCONF HZCLIBX1 HZCLIBX4 HZCLIBSO HZCZLIBZ
  HZCLIBS4 HZCLIBXX HZCLIBZZ
  

Fix information

• Fixed component name

  UNIX SS COMPLIB

• Fixed component ID

  5695SCPX7

Applicable component levels

• R7A0 PSY UJ00877

     UP19/10/23 P F910

• R7B0 PSY UJ00875

     UP19/10/23 P F910

• R7C0 PSY UJ00876

     UP19/10/23 P F910

Fix is available

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