policy namespace stacking

This bug was fixed in the package linux - 4.4.0-15.31

---------------
linux (4.4.0-15.31) xenial; urgency=low

  [ Tim Gardner ]

  * Release Tracking Bug
    - LP: #1559252

  * Xilinx KU3 Capi card does not show up in Ubuntu 16.04 (LP: #1557001)
    - SAUCE: (noup) cxl: Allow initialization on timebase sync failures

  * policy namespace stacking (LP: #1379535)
    - Revert "UBUNTU: SAUCE: Move replacedby allocation into label_alloc"
    - Revert "UBUNTU: SAUCE: Fixup: __label_update() still doesn't handle some cases correctly."
    - Revert "UBUNTU: SAUCE: fix: audit "no_new_privs" case for exec failure"
    - Revert "UBUNTU: SAUCE: fixup: warning about aa_label_vec_find_or_create not being static"
    - Revert "UBUNTU: SAUCE: apparmor: fix refcount race when finding a child profile"
    - Revert "UBUNTU: SAUCE: fixup: cast poison values to remove warnings"
    - Revert "UBUNTU: SAUCE: fixup: get rid of unused var build warning"
    - Revert "UBUNTU: SAUCE: fixup: 20/23 locking issue around in __label_update"
    - Revert "UBUNTU: SAUCE: fixup: make __share_replacedby private to get rid of build warning"
    - Revert "UBUNTU: SAUCE: fix: replacedby forwarding is not being properly update when ns is destroyed"
    - Revert "UBUNTU: SAUCE: apparmor: fix log of apparmor audit message when kern_path() fails"
    - Revert "UBUNTU: SAUCE: fixup: cleanup return handling of labels"
    - Revert "UBUNTU: SAUCE: apparmor: fix: ref count leak when profile sha1 hash is read"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: query label file permission"
    - Revert "UBUNTU: SAUCE: apparmor: Don't remove label on rcu callback if the label has already been removed"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: break circular refcount for label that is directly freed."
    - Revert "UBUNTU: SAUCE: apparmor: Fix: refcount bug when inserting label update that transitions ns"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: now that insert can force replacement use it instead of remove_and_insert"
    - Revert "UBUNTU: SAUCE: apparmor Fix: refcount bug in pivotroot mediation"
    - Revert "UBUNTU: SAUCE: apparmor: ensure that repacedby sharing is done correctly"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: update replacedby allocation to take a gfp parameter"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: convert replacedby update to be protected by the labelset lock"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: add required locking of __aa_update_replacedby on merge path"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: deadlock in aa_put_label() call chain"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: label_vec_merge insertion"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: ensure new labels resulting from merge have a replacedby"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: refcount leak in aa_label_merge"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: refcount race between locating in labelset and get"
    - Revert "UBUNTU: SAUCE: apparmor: Fix: label merge handling of marking unconfined and stale"
    - Revert "UBUNTU: SAUCE: apparmor: add underscores to indicate aa_label_next_not_in_set() use needs locking"
    - Revert "UBUNTU: SAUCE: apparmor: debug: POISON label and replaceby ...

This bug was fixed in the package apparmor - 2.10.95-0ubuntu1

---------------
apparmor (2.10.95-0ubuntu1) xenial; urgency=medium

  * Update to apparmor 2.10.95 (2.11 Beta 1) (LP: #1561762)
    - Allow Apache prefork profile to chown(2) files (LP: #1210514)
    - Allow deluge-gtk and deluge-console to handle torrents opened in
      browsers (LP: #1501913)
    - Allow file accesses needed by some programs using libnl-3-200
      (Closes: #810888)
    - Allow file accesses needed on systems that use NetworkManager without
      resolvconf (Closes: #813835)
    - Adjust aa-status(8) to work without python3-apparmor (LP: #1480492)
    - Fix aa-logprof(8) crash when operating on files containing multiple
      profiles with certain rules (LP: #1528139)
    - Fix log parsing crashes, in the Python utilities, caused by certain file
      related events (LP: #1525119, LP: #1540562)
    - Fix log parsing crasher, in the Python utilities, caused by certain
      change_hat events (LP: #1523297)
    - Improve Python 2 support of the utils by fixing an aa-logprof(8) crasher
      when Python 3 is not available (LP: #1513880)
    - Send aa-easyprof(8) error messages to stderr instead of stdout
      (LP: #1521400)
    - Fix aa-autodep(8) failure when the shebang line of a script contained
      parameters (LP: #1505775)
    - Don't depend on the system logprof.conf when running utils/ build tests
      (LP: #1393979)
    - Fix apparmor_parser(8) bugs when parsing profiles that use policy
      namespaces in the profile declaration or profile transition targets
      (LP: #1540666, LP: #1544387)
    - Regression fix for apparmor_parser(8) bug that resulted in the
      --namespace-string commandline option being ignored causing profiles to
      be loaded into the root policy namespace (LP: #1526085)
    - Fix crasher regression in apparmor_parser(8) when the parser was asked
      to process a directory (LP: #1534405)
    - Fix bug in apparmor_parser(8) to honor the specified bind flags remount
      rules (LP: #1272028)
    - Support tarball generation for Coverity scans and fix a number of issues
      discovered by Coverity
    - Fix regression test failures on s390x systems (LP: #1531325)
    - Adjust expected errno values in changeprofile regression test
      (LP: #1559705)
    - The Python utils gained support for ptrace and signal rules
    - aa-exec(8) received a rewrite in C
    - apparmor_parser(8) gained support for stacking multiple profiles, as
      supported by the Xenial kernel (LP: #1379535)
    - libapparmor gained new public interfaces, aa_stack_profile(2) and
      aa_stack_onexec(2), allowing applications to utilize the new kernel
      stacking support (LP: #1379535)
  * Drop the following patches since they've been incorporated upstream:
    - aa-status-dont_require_python3-apparmor.patch
    - r3209-dnsmasq-allow-dash
    - r3227-locale-indep-capabilities-sorting.patch
    - r3277-update-python-abstraction.patch
    - r3366-networkd.patch,
    - tests-fix_sysctl_test.patch
    - parser-fix-cache-file-mtime-regression.patch
    - parser-verify-cache-file-mtime.patch
    - parser-run-caching-tests-without-apparmorfs.patch
    - pa...

I see this is "Fix Released" everywhere but on the upstream AppArmor project. I understand this has made its way upstream and works with mainline kernel, e.g. for LXC. If my understanding is incorrect, please clarify what's left to do here (or perhaps track it on a finer-grained follow-up bug :)

This is indeed upstream, and works as far as it goes. There are currently issues when crossing system namespace boundaries but those are being treated as separate issues. The stacking it self works policy when crossing ns boundaries has to be aware of it and more relaxed than we would like.