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[Stéphane Graber <1645037@xxxxxxxxxxxxxxxxxx>]

** No longer affects: apparmor (Ubuntu)

** No longer affects: linux (Ubuntu Xenial)

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

Title:
  apparmor_parser hangs indefinitely when called by multiple threads

Status in linux package in Ubuntu:
  Fix Released
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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