IJ48364: ZLIBNX MAY GENERATE COMPRESSED FILES THAT CAN'T BE UNCOMPRESSED APPLIES TO AIX 7300-03

APAR status

• Closed as program error.

Error description

• zlibNX using HW acceleration on P9/P10 can generate
  incorrect compressed files
  that can't be uncompressed.
  This happens in the rare case where deflate is called
  with Z_FINISH and the
  "compressed" data is significantly bigger than the input
  (not compressed) data
  so that the output buffer passed to the accelerator is
  too small.
  In this case, the accelerator returns an error as
  expected.
  zlibNX catches it and falls back to SW compression.
  There is a bug in the fallback path that leads to
  incorrect compressed data
  being generated with no error or warning reported. The
  resulting file can't
  be uncompressed and the data may be lost.
  This case has not been seen with the standard compress
  tools (xgzip or pigz)
  but has been seen with DB2 compression.
  

Local fix

Problem summary

• when decompressing, the decompression stops on the first
  BFINAL which is in the middle of the file and it fails
  With below error.
  pigz -c -d bad.gz > /tmp/bad
  pigz: skipping: bad.gz: corrupted -- crc32 mismatch
  

Problem conclusion

• Avoid setting the Completion of the Compression prematurely.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  IJ47907

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  AIX V7.3

• Fixed component ID

  5765CD300

Applicable component levels