[Bug 863629] Re: libvirt-lxc: virFileOpenTtyAt can't be called on /some/other/dev/pts

[Martin Pitt]

** Tags removed: verification-needed
** Tags added: verification-done

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Title:
  libvirt-lxc: virFileOpenTtyAt can't be called on /some/other/dev/pts

Status in “libvirt” package in Ubuntu:
  Fix Released
Status in “libvirt” source package in Lucid:
  New
Status in “libvirt” source package in Maverick:
  New
Status in “libvirt” source package in Natty:
  New
Status in “libvirt” source package in Oneiric:
  Fix Committed

Bug description:
  lxcControllerRun() is calling virFileOpenTtyAt() with a slave opened
  on /the/container/chroot/dev/pts.  While it is not documented in the
  manpages, glibc's grantpt does a first check (ensuring that the passed
  in fd is a pty slave) with '/dev/pts' as the hardcoded path, appending
  the pty#.

  lxcControllerRun always calls this on the first slave opened after
  creating the new /dev/pts, so grantpt is always checking /dev/pts/0.
  Therefore, if your host does not have /dev/pts/0 (easy to reproduce
  using screen), then grantpt will fail, and the container creation will
  subsequently also fail.

  =================================================================
  SRU Justification:

  1. Impact: libvirt will be unable to create lxc containers, saying that it cannot allocate /dev/pts/0
  2. Development fix: A patch was sent upstream which makes libvirt-lxc not use glibc's grantpt, which is the cause of the bug.
  3. Stable fix: same as the development fix.
  4. Test case:
     0. [ Set up libvirt and create a libvirt-lxc container ]
     1. make sure noone is logged into the server
     2. log in, make sure your tty is /dev/pts/0 (check with 'tty')
     3. Pin /dev/pts/0 by doing "sleep 2h & disown; exit"
     4. Try to start a container on that system.  Without this fix it will fail with an error about /dev/pts/0.
     5. Regression potential: if the patch was bad, it could cause failures when starting a container, or other places when libvirt allocates a tty.
  =================================================================

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