[Bug 1833479] Re: libjack-jackd2-0 double close on a failure to connect to jackd which causes crashes in multithreaded programs

[Mathew Hodson]

** Changed in: jackd2 (Ubuntu)
   Importance: Undecided => High

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Title:
  libjack-jackd2-0 double close on a failure to connect to jackd which
  causes crashes in multithreaded programs

Status in jackd2 package in Ubuntu:
  New
Status in jackd2 package in Debian:
  New

Bug description:
  After upgrading to Ubuntu 19.04, I started experiencing sporadic
  crashes in kodi when turning my AV receiver on. Ubuntu 19.04 upgraded
  alsa-plugins to 1.1.8. For alsa-plugins >= 1.1.7, the ALSA jack plugin
  is enabled by default in /etc/alsa/conf.d/50-jack.conf.

  The crashes are caused by a race condition when kodi's audio engine
  thread is enumerating the ALSA sound devices, and the udev thread is
  enumerating the udev devices triggered by the sound device add from
  turning the AVR on.

  When enumerating the ALSA jack plugin device, it tries to connect to
  connect to jackd. Since I don't have jackd installed, it fails to
  connect. libjack closes the socket on error, and then closes it again
  in it's cleanup code. Since it's closing the same file descriptor
  twice, it interacts with other threads that have potentially opened
  file descriptors, and causes the crash.

  This same bug could potentially affect other multi-threaded programs
  that enumerate ALSA devices.

  Fix committed upstream:
  https://github.com/jackaudio/jack2/commit/dad4b5702782eef3bd66e3c3f4fefaaae3571208

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