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[Andy Whitcroft <apw@xxxxxxxxxxxxx>]

This bug was nominated against a series that is no longer supported, ie
yakkety.  The bug task representing the yakkety nomination is being
closed as Won't Fix.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu Yakkety)
       Status: Triaged => Won't Fix

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https://bugs.launchpad.net/bugs/1645037

Title:
  apparmor_parser hangs indefinitely when called by multiple threads

Status in apparmor package in Ubuntu:
  Triaged
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  Triaged
Status in linux source package in Yakkety:
  Won't Fix
Status in linux source package in Zesty:
  Fix Released

Bug description:
  This bug surfaced when starting ~50 LXC container with LXD in parallel
  multiple times:

  # Create the containers
  for c in c foo{1..50}; do lxc launch images:ubuntu/xenial $c; done

  # Exectute this loop multiple times until you observe errors.
  for c in c foo{1..50}; do lxc restart $c & done

  After this you can

  ps aux | grep apparmor

  and you should see output similar to:

  root     19774  0.0  0.0  12524  1116 pts/1    S+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo30
  root     19775  0.0  0.0  12524  1208 pts/1    S+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo26
  root     19776  0.0  0.0  13592  3224 pts/1    D+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo30
  root     19778  0.0  0.0  13592  3384 pts/1    D+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo26
  root     19780  0.0  0.0  12524  1208 pts/1    S+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo43
  root     19782  0.0  0.0  12524  1208 pts/1    S+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo34
  root     19783  0.0  0.0  13592  3388 pts/1    D+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo43
  root     19784  0.0  0.0  13592  3252 pts/1    D+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo34
  root     19794  0.0  0.0  12524  1208 pts/1    S+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo25
  root     19795  0.0  0.0  13592  3256 pts/1    D+   20:14   0:00 apparmor_parser -RWL /var/lib/lxd/security/apparmor/cache /var/lib/lxd/security/apparmor/profiles/lxd-foo25

  apparmor_parser remains stuck even after all LXC/LXD commands have
  exited.

  dmesg output yields lines like:

  [41902.815174] audit: type=1400 audit(1480191089.678:43):
  apparmor="STATUS" operation="profile_load" profile="unconfined" name
  ="lxd-foo30_</var/lib/lxd>" pid=12545 comm="apparmor_parser"

  and cat /proc/12545/stack shows:

  [<ffffffff8c9b9378>] aa_remove_profiles+0x88/0x270
  21:19   brauner  [<ffffffff8c9ac3e4>] profile_remove+0x144/0x2e0
  21:19   brauner  [<ffffffff8c8319b8>] __vfs_write+0x18/0x40
  21:19   brauner  [<ffffffff8c832108>] vfs_write+0xb8/0x1b0
  21:19   brauner  [<ffffffff8c833565>] SyS_write+0x55/0xc0
  21:19   brauner  [<ffffffff8ce952f6>] entry_SYSCALL_64_fastpath+0x1e/0xa8
  21:19   brauner  [<ffffffffffffffff>] 0xffffffffffffffff

  This looks like a potential kernel bug.

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