Hello bugproxy, or anyone else affected,

Accepted zlib into focal-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/zlib/1:1.2.11.dfsg-
2ubuntu1.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: zlib (Ubuntu Focal)
       Status: New => Fix Committed

** Tags added: verification-needed verification-needed-focal

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  [Ubuntu 20.10] zlib: DFLTCC compression level switching issues

Status in Ubuntu on IBM z Systems:
  In Progress
Status in zlib package in Ubuntu:
  Fix Released
Status in zlib source package in Focal:
  Fix Committed
Status in zlib source package in Groovy:
  Fix Released

Bug description:
  SRU Justification:


   * This SRU fixes a combination of multiple issues:

   * zlib DFLTCC compression level switching can corrupt data because
  hardware and software compression states become desynchronized. (LP

   * Since zlib is not working on all s390x system configurations
  support for switching between software and hardware compression is
  required especially for Java. (LP 1882494)

   * zlib on s390x may produce incomplete raw streams (but not
  gzip/zlib). (LP 1889059)

  [Test Case]

   * Since especially DFLTCC requires a s390x generation z15 or LinuxONE
  III the tests need to be done by IBM.

   * IBM has a set of tests available, that exercise public zlib APIs by
  calling them in different sequences with different buffer sizes and
  flush modes.

  * Partially these come from the IBM z/OS team, who developed their own
  zlib support for the hardware accelerator, and partially they are
  developed by the IBM Linux team based on issues encountered during
  development as well as fuzzing.

  * IBM also uses the zlib-ng test-suite as well as squash and stress-

   * Compress data using zlib/DFLTCC with different compression level
  and verify state and if data got corrupted or not. (LP 1893170)

   * On a system with patched zlib package, switch between hardware and
  software compression and use zlib via the java.util.zip package
  (LP 1882494)

  * On a z15 system with hardware acceleration compression (DFLTCC)
  enabled, create a raw (negative windowBits value) stream with zlib.
  Then check if EOBS is missing or truncated. (LP 1889059)

  [Regression Potential]

   * There is a certain risk for regressions with the modifications that
  are introduced by the four LP bugs.

   * In case the package fails entirely, it will have (in worst case) an
  impact on all zlib, gzip and DFLTCC compression/decompression
  functions, that are very wide spread (gzip, tar cfz, everything with
  zlib) in Linux and would virtually make the system unusable.

   * If potential issues are limited to hardware assisted compression
  (which is more likely, since these patches are mostly about hw
  assisted compression), then issues would be limited to systems that
  provide this feature (latest s390x generation only).

  * A switch back to software got introduced (by setting DFLTCC=0
  environment variable) that will help to mitigate a potential negative
  impact of the hw assisted compression.

   * Only the latest s390x generation (z15 and LinuxONE III) supports
  hardware assisted DFLTCC and is potentially affected.

   * A patched test package was made available and got successfully
  tested by IBM. All four bugs were finally considered as solved with
  zlib (1:1.2.11.dfsg-2ubuntu2~ppa2) available here:


  Description:   zlib: DFLTCC compression level switching issues
  Symptom:       Switching compression levels corrupts data
  Problem:       Hardware and software compression states become desynchronized.
  Solution:      Improve compression state synchronization. Since zlib project
                 does not accept patches at the moment, the fix has been
                 integrated into the DFLTCC pull request:
                 The commitid is 992a7afc3edfa511dff0650d1c545b11bf64e655.
  Reproduction:  Not possible with popular command line tools. The issues were
                 discovered using example_call_fuzzer from:

  This needs also be applied against 20.04 !

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