Validate default_kernel global property on set

fixes: QubesOS/qubes-issues#8992

qubes/app.py

@@ -1593,3 +1593,13 @@ def on_property_set_default_dispvm(self, event, name, newvalue,
  # resetting dispvm to its default value
  vm.fire_event('property-reset:default_dispvm',
  name='default_dispvm', oldvalue=oldvalue)
+
+ @qubes.events.handler('property-pre-set:default_kernel')
+ # pylint: disable-next=invalid-name
+ def on_property_pre_set_default_kernel(self, event, name, newvalue,
+ oldvalue=None):
+ # pylint: disable=unused-argument
+ kernels = [kernel.vid for kernel in self.pools['linux-kernel'].volumes]
+ if not newvalue in kernels:
+ raise qubes.exc.QubesException(
+ 'Invalid kernel: {} !'.format(newvalue))

run-tests

@@ -19,6 +19,13 @@ if sudo --non-interactive "$name/ci/lvm-manage" setup-lvm vg$$/pool; then
  CLEANUP_LVM=yes
 fi
 
+CLEANUP_KERNEL_POOL=
+if [ ! -d "/var/lib/qubes/vm-kernels" ]; then
+ sudo mkdir --parents /var/lib/qubes/vm-kernels/dummy
+ sudo mkdir --parents /var/lib/qubes/vm-kernels/1.0
+ CLEANUP_KERNEL_POOL=yes
+fi
+
 : "${PYTHON:=python3}"
 : "${TESTPYTHONPATH:=test-packages}"
 
@@ -32,6 +39,11 @@ export PYTHONPATH
 "${PYTHON}" setup.py egg_info --egg-base "${TESTPYTHONPATH}"
 "${PYTHON}" -m coverage run --rcfile=ci/coveragerc -m qubes.tests.run "$@"
 retcode=$?
+if [ -n "$CLEANUP_KERNEL_POOL" ]; then
+ sudo rmdir /var/lib/qubes/vm-kernels/dummy
+ sudo rmdir /var/lib/qubes/vm-kernels/1.0
+ sudo rmdir /var/lib/qubes/vm-kernels
+fi
 if [ -n "$CLEANUP_LVM" ]; then
  sudo --non-interactive $(dirname "$0")/ci/lvm-manage cleanup-lvm "$DEFAULT_LVM_POOL"
 fi