[Bug 1778547] Re: Broken system lock counting

[Chris J Arges]

Hello Julian, or anyone else affected,

Accepted apt into xenial-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/apt/1.2.27 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 and change the tag from
verification-needed-xenial to verification-done-xenial. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-xenial. 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!

** Changed in: apt (Ubuntu Xenial)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-xenial

** Changed in: apt (Ubuntu Artful)
       Status: In Progress => Fix Committed

** Tags added: verification-needed-artful

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to apt in Ubuntu.
https://bugs.launchpad.net/bugs/1778547

Title:
  Broken system lock counting

Status in apt package in Ubuntu:
  Fix Committed
Status in apt source package in Xenial:
  Fix Committed
Status in apt source package in Artful:
  Fix Committed
Status in apt source package in Bionic:
  Fix Committed

Bug description:
  [Impact]
  System lock unrefing is broken, off-by-one error. Locking twice opens a second fd for the lock file, and the old fd gets lost and remains open for the remaining duration of the program

  [Test case]

  Executing the following script should show one lock file in the first
  line, and none in the last line.

  def maybe_readlink(path):
    try:
      return os.readlink("/proc/self/fd/" + p)
    except:
      return "<deleted>"

  import os, apt_pkg
  apt_pkg.init()
  apt_pkg.pkgsystem_lock()
  apt_pkg.pkgsystem_lock()
  apt_pkg.pkgsystem_unlock()
  apt_pkg.pkgsystem_unlock()
  print([(p, maybe_readlink("/proc/self/fd/" + p)) for p in os.listdir("/proc/self/fd")])

  
  [Test output]
  good, cosmic:
  [('0', '/dev/pts/2'), ('1', '/dev/pts/2'), ('2', '/dev/pts/2'), ('3', '/var/lib/dpkg/lock'), ('4', '<deleted>')]
  [('0', '/dev/pts/2'), ('1', '/dev/pts/2'), ('2', '/dev/pts/2'), ('3', '<deleted>')]

  bad, bionic:
  [('0', '/dev/pts/0'), ('1', '/dev/pts/0'), ('2', '/dev/pts/0'), ('3', 'pipe:[40889331]'), ('4', '/var/lib/dpkg/lock'), ('5', '/var/lib/dpkg/lock'), ('6', '<deleted>'), ('17', 'socket:[53931]')]
  [('0', '/dev/pts/0'), ('1', '/dev/pts/0'), ('2', '/dev/pts/0'), ('3', 'pipe:[40889331]'), ('4', '/var/lib/dpkg/lock'), ('5', '<deleted>'), ('17', 'socket:[53931]')]

  
  [Regression potential]
  A locking change can potentially break locking, but this one seems like an obvious off-by-one error.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1778547/+subscriptions