windows: fix terminating processes

The neutron Windows exec call helper doesn't properly handle the
situation in which the process that it's trying to kill was already
terminated, in which case using wmi to fetch the process can raise
an exception.

This change ensures that those WMI exceptions will be properly
handled.

Closes-Bug: 1872663

Change-Id: I00c810fe541ac5e1e9923155fe90eb07a0b4b3dd
(cherry picked from commit 8fd3e884c7)

neutron/agent/windows/utils.py

@@ -13,6 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import ctypes
 import io
 import os
 
@@ -37,6 +38,8 @@ LOG = logging.getLogger(__name__)
 subprocess = eventlet.patcher.original('subprocess')
 subprocess.threading = eventlet.patcher.original('threading')
 
+ERROR_KEY_DELETED = 0x03FA
+
 
 def create_process(cmd, run_as_root=False, addl_env=None,
                    tpool_proxy=True):
@@ -70,8 +73,16 @@ def _get_wmi_process(pid):
     if not pid:
         return None
 
+    try:
         conn = wmi.WMI()
         processes = conn.Win32_Process(ProcessId=pid)
+    except wmi.x_wmi as exc:
+        hresult = exc.com_error.hresult
+        err_code = ctypes.c_uint(hresult).value & 0xFFFF
+        if err_code == ERROR_KEY_DELETED:
+            return None
+        raise
+
     if processes:
         return processes[0]
     return None

neutron/tests/unit/agent/windows/test_utils.py

@@ -26,6 +26,13 @@ from neutron.common import exceptions
 from neutron.tests import base
 
 
+class x_wmi(Exception):
+    def __init__(self, info='', com_error=None):
+        super(x_wmi, self).__init__(info)
+        self.info = info
+        self.com_error = com_error
+
+
 @ddt.ddt
 class WindowsUtilsTestCase(base.BaseTestCase):
     @mock.patch('os.environ', {mock.sentinel.key0: mock.sentinel.val0})
@@ -87,6 +94,25 @@ class WindowsUtilsTestCase(base.BaseTestCase):
         if pid:
             mock_conn.Win32_Process.assert_called_once_with(ProcessId=pid)
 
+    @ddt.data({},
+              {"hresult": 0xff,
+               "expect_exc": True})
+    @ddt.unpack
+    @mock.patch.object(utils, 'wmi', create=True)
+    def test_get_wmi_process_exc(self, mock_wmi, expect_exc=False,
+                                 hresult=0x800703FA):
+        mock_conn = mock_wmi.WMI.return_value
+        mock_wmi.x_wmi = x_wmi
+        com_error = mock.Mock(hresult=hresult)
+        exc = x_wmi(com_error=com_error)
+        mock_conn.Win32_Process.side_effect = exc
+
+        if expect_exc:
+            self.assertRaises(
+                x_wmi, utils._get_wmi_process, mock.sentinel.pid)
+        else:
+            self.assertIsNone(utils._get_wmi_process(mock.sentinel.pid))
+
     @ddt.data(True, False)
     @mock.patch.object(utils, '_get_wmi_process')
     def test_kill_process(self, process_exists, mock_get_process):