[Bug 1927519] Re: Mitigate libvirt: error : unable to set AppArmor profile 'libvirt-<vm-uuid>' for '/usr/bin/kvm-spice': No such file or directory

[Ioanna Alifieraki]

VERIFICATION QUEENS

Installed libvirt form queens-proposed

dpkg -l | grep libvirt

ii  libvirt-bin                            4.0.0-1ubuntu8.20~cloud0                        amd64        programs for the libvirt library
ii  libvirt-clients                        4.0.0-1ubuntu8.20~cloud0                        amd64        Programs for the libvirt library
ii  libvirt-daemon                         4.0.0-1ubuntu8.20~cloud0                        amd64        Virtualization daemon
ii  libvirt-daemon-driver-storage-rbd      4.0.0-1ubuntu8.20~cloud0                        amd64        Virtualization daemon RBD storage driver
ii  libvirt-daemon-system                  4.0.0-1ubuntu8.20~cloud0                        amd64        Libvirt daemon configuration files
ii  libvirt0:amd64                         4.0.0-1ubuntu8.20~cloud0                        amd64        library for interfacing with different virtualization systems


# virsh dominfo ctest1
Id:             -
Name:           ctest1
UUID:           2fadfa2d-28d8-4bbc-8b31-dfb871881b7e
OS Type:        hvm
State:          shut off
CPU(s):         1
Max memory:     1048576 KiB
Used memory:    1048576 KiB
Persistent:     yes
Autostart:      disable
Managed save:   no
Security model: apparmor
Security DOI:   0


#  cat /dev/null | sudo tee /etc/apparmor.d/libvirt/libvirt-2fadfa2d-28d8-4bbc-8b31-dfb871881b7e

# virsh start ctest1
Domain ctest1 started

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https://bugs.launchpad.net/bugs/1927519

Title:
  Mitigate libvirt: error : unable to set AppArmor profile 'libvirt-<vm-
  uuid>' for '/usr/bin/kvm-spice': No such file or directory

Status in Ubuntu Cloud Archive:
  Fix Committed
Status in Ubuntu Cloud Archive queens series:
  Fix Committed
Status in Ubuntu Cloud Archive stein series:
  Fix Committed
Status in Ubuntu Cloud Archive ussuri series:
  Fix Committed
Status in libvirt package in Ubuntu:
  Fix Committed
Status in libvirt source package in Bionic:
  Fix Released
Status in libvirt source package in Focal:
  Fix Released
Status in libvirt source package in Hirsute:
  Fix Released
Status in libvirt source package in Impish:
  Fix Released
Status in libvirt source package in Jammy:
  Fix Committed

Bug description:
  [Impact]

  Some times libvirt fails to start a vm with the following error :
  libvirt:  error : unable to set AppArmor profile 'libvirt-b05b297f-952f-42d6-b04e-f9a13767db54' for '/usr/bin/kvm-spice': No such file or directory

  This happens because for some reason the apparmor profile for the
  guest /etc/apparmor.d/libvirt/libvirt-<vm-uuid> has 0 size.

  We do not now why the above file gets truncated to begin with and
  therefore we do not know the root cause to fix it there. But the
  condition is easy to detect and 100% broken, so we can detect and
  recreate the file in those cases.

  [Test case]

  To reproduce this behaviour, create a vm and stop it, note the uuid.

  For example:
  $ uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily arch=amd64 label=daily release=focal
  $ uvt-kvm create --password=ubuntu f release=focal arch=amd64 label=daily
  $ virsh dominfo f
  ...
  Security label: libvirt-1ceac8db-c1e9-40b2-8ada-a60349454fc1 (enforcing)
  $ virsh shutdown f

  Then make the start apparmor profile an empty file.
  On Bionic/Focal that file will be non-existant by default (cleaned on guest stop), on Hirsute/Impish it will be around for admin-edit but with content. Therefore "touch" isn't enough every time, instead really put nothing to it as that is how the real issue looks like).

  $ cat /dev/null | sudo tee /etc/apparmor.d/libvirt/libvirt-1ceac8db-c1e9-40b2-8ada-a60349454fc1
  # ensure it is size zero
  $ ll /etc/apparmor.d/libvirt/libvirt-1ceac8db-c1e9-40b2-8ada-a60349454fc1
  -rw-r--r-- 1 root root 0 Nov 18 09:01 /etc/apparmor.d/libvirt/libvirt-1ceac8db-c1e9-40b2-8ada-a60349454fc1

  Next try to start the vm, it will try to use the file it found
  (instead of creating a new one as it would when non-existing) and will
  fail doing so:

  $ virsh start f
  error: internal error: Process exited prior to exec: libvirt:  error : unable to set AppArmor profile 'libvirt-1ceac8db-c1e9-40b2-8ada-a60349454fc1' for '/usr/bin/qemu-system-x86_64': No such file or directory

  To manually be able to start the vm again just delete the libvirt-<vm-uuid> file.
  With the fix applied libvirt will recreate the file and guest start works again.

  
  In addition (independent to the case) I'll run a set of common regression tests against <release>-proposed which didn't run for a while and would make us also spot if anything other slipped in from different places (like the dwarves hiccup we had). Since testing shall be on "the real build" and resources are limited I'd this time do so only on the builds in proposed.

  [Regression Potential]

  The new code is only active when the size of the file is zero which is
  a 100% guarantee that the guest is broken and won't start.
  Nevertheless if we made a mistake in the fix the area (of the many
  things libvirt does) to look at is the generating and usage of
  apparmor profiles.

  [Other]

  Similar reported bug : https://bugs.debian.org/cgi-
  bin/bugreport.cgi?bug=890084

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