openstack/virtualbmc
Code Issues Proposed changes

Fix hanging on shell-pipe

Browse Source 
Properly closes standard I/O streams to prevent shell-piped
processes from hanging infinitely on a dead pipe.

Change-Id: Id9dedac4f778cf37d626f2777d519f73cc4b5f2c
Story: 2007219
Task: 38471
This commit is contained in:
Ilya Etingof 2020-02-18 19:39:42 +01:00
parent 834d02e616
commit 2651f13f28
6 changed files with 87 additions and 70 deletions
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5
releasenotes/notes/fix-hanging-on-pipe-7c4b5f9c81623b524.yaml Normal file
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@ -0,0 +1,5 @@
---
fixes:
- |
Properly closes standard I/O streams to prevent shell-piped processes from
hanging infinitely on a dead pipe.

9
virtualbmc/cmd/vbmc.py
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@ -12,7 +12,6 @@
import json
import logging
import os
import sys
import time
@ -28,6 +27,7 @@ from virtualbmc.cmd import vbmcd
from virtualbmc import config as vbmc_config
from virtualbmc.exception import VirtualBMCError
from virtualbmc import log
from virtualbmc import utils
CONF = vbmc_config.get_config()
@ -110,9 +110,10 @@ class ZmqClient(object):
"future releases!")
# attempt to start and daemonize the server
if os.fork() == 0:
# this will also fork and detach properly
vbmcd.main([])
with utils.detach_process() as pid:
if pid == 0:
# NOTE(etingof): this child will never return
vbmcd.main(['--foreground'])
# TODO(etingof): perform some more retries
time.sleep(CONF['default']['server_spawn_wait'] / 1000.)

5
virtualbmc/cmd/vbmcd.py
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@ -85,9 +85,14 @@ def main(argv=sys.argv[1:]):
if args.foreground:
return wrap_with_pidfile(control.application, os.getpid())
else:
with utils.detach_process() as pid:
if pid > 0:
return 0
return wrap_with_pidfile(control.application, pid)
if __name__ == '__main__':
sys.exit(main())

21
virtualbmc/tests/unit/cmd/test_vbmcd.py
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@ -30,22 +30,23 @@ class VBMCDTestCase(base.TestCase):
@mock.patch.object(os, 'kill')
@mock.patch.object(os, 'unlink')
def test_main_foreground(self, mock_unlink, mock_kill, mock_open):
with mock.patch.object(control, 'application') as ml:
with mock.patch.object(control, 'application') as mock_ml:
mock_kill.side_effect = OSError()
vbmcd.main(['--foreground'])
mock_kill.assert_called_once()
ml.assert_called_once()
mock_ml.assert_called_once()
mock_unlink.assert_called_once()
@mock.patch.object(builtins, 'open')
@mock.patch.object(os, 'kill')
@mock.patch.object(os, 'unlink')
def test_main_background(self, mock_unlink, mock_kill, mock_open):
with mock.patch.object(utils, 'detach_process') as dp, \
mock.patch.object(control, 'application') as ml:
mock_kill.side_effect = OSError()
vbmcd.main([])
mock_kill.assert_called_once()
dp.assert_called_once()
ml.assert_called_once()
mock_unlink.assert_called_once()
with mock.patch.object(utils, 'detach_process') as mock_dp:
with mock.patch.object(control, 'application') as mock_ml:
mock_kill.side_effect = OSError()
mock_dp.return_value.__enter__.return_value = 0
vbmcd.main([])
mock_kill.assert_called_once()
mock_dp.assert_called_once()
mock_ml.assert_called_once()
mock_unlink.assert_called_once()

81
virtualbmc/tests/unit/test_utils.py
View File

@ -114,60 +114,49 @@ class LibvirtUtilsTestCase(base.TestCase):
self._test_libvirt_open_sasl(readonly=True)
@mock.patch.object(os, 'getpid')
@mock.patch.object(os, 'umask')
@mock.patch.object(os, 'chdir')
@mock.patch.object(os, 'setsid')
@mock.patch.object(os, '_exit')
@mock.patch.object(os, 'fork')
@mock.patch.object(utils, 'os')
class DetachProcessUtilsTestCase(base.TestCase):
def test_detach_process(self, mock_fork, mock__exit, mock_setsid,
mock_chdir, mock_umask, mock_getpid):
def test_detach_process(self, mock_os):
# 2nd value > 0 so _exit get called and we can assert that we've
# killed the parent's process
mock_fork.side_effect = (0, 999)
mock_os.fork.side_effect = (0, 999)
mock_os.devnull = os.devnull
mock_getpid.return_value = 123
with utils.detach_process() as pid:
self.assertEqual(123, pid)
self.assertEqual(0, pid)
# assert fork() has been called twice
expected_fork_calls = [mock.call()] * 2
self.assertEqual(expected_fork_calls, mock_fork.call_args_list)
self.assertEqual(expected_fork_calls, mock_os.fork.call_args_list)
mock_setsid.assert_called_once_with()
mock_chdir.assert_called_once_with('/')
mock_umask.assert_called_once_with(0)
mock__exit.assert_called_once_with(0)
mock_getpid.assert_called_once_with()
mock_os.setsid.assert_called_once_with()
mock_os.chdir.assert_called_once_with('/')
mock_os.umask.assert_called_once_with(0)
mock_os._exit.assert_called_once_with(0)
def test_detach_process_fork_fail(self, mock_fork, mock__exit, mock_setsid,
mock_chdir, mock_umask, mock_getpid):
def test_detach_process_fork_fail(self, mock_os):
error_msg = 'Kare-a-tay!'
mock_fork.side_effect = OSError(error_msg)
mock_os.fork.side_effect = OSError(error_msg)
with self.assertRaisesRegex(exception.DetachProcessError, error_msg):
with utils.detach_process():
pass
mock_fork.assert_called_once_with()
self.assertFalse(mock_setsid.called)
self.assertFalse(mock_chdir.called)
self.assertFalse(mock_umask.called)
self.assertFalse(mock__exit.called)
self.assertFalse(mock_getpid.called)
mock_os.fork.assert_called_once_with()
self.assertFalse(mock_os.setsid.called)
self.assertFalse(mock_os.chdir.called)
self.assertFalse(mock_os.umask.called)
self.assertFalse(mock_os._exit.called)
def test_detach_process_chdir_fail(self, mock_fork, mock__exit,
mock_setsid, mock_chdir, mock_umask,
mock_getpid):
def test_detach_process_chdir_fail(self, mock_os):
# 2nd value > 0 so _exit get called and we can assert that we've
# killed the parent's process
mock_fork.side_effect = (0, 999)
mock_os.fork.side_effect = (0, 999)
error_msg = 'Fish paste!'
mock_chdir.side_effect = Exception(error_msg)
mock_os.chdir.side_effect = Exception(error_msg)
with self.assertRaisesRegex(exception.DetachProcessError, error_msg):
with utils.detach_process():
@ -175,23 +164,20 @@ class DetachProcessUtilsTestCase(base.TestCase):
# assert fork() has been called twice
expected_fork_calls = [mock.call()] * 2
self.assertEqual(expected_fork_calls, mock_fork.call_args_list)
self.assertEqual(expected_fork_calls, mock_os.fork.call_args_list)
mock_setsid.assert_called_once_with()
mock_chdir.assert_called_once_with('/')
mock__exit.assert_called_once_with(0)
self.assertFalse(mock_umask.called)
self.assertFalse(mock_getpid.called)
mock_os.setsid.assert_called_once_with()
mock_os.chdir.assert_called_once_with('/')
mock_os._exit.assert_called_once_with(0)
self.assertFalse(mock_os.umask.called)
def test_detach_process_umask_fail(self, mock_fork, mock__exit,
mock_setsid, mock_chdir, mock_umask,
mock_getpid):
def test_detach_process_umask_fail(self, mock_os):
# 2nd value > 0 so _exit get called and we can assert that we've
# killed the parent's process
mock_fork.side_effect = (0, 999)
mock_os.fork.side_effect = (0, 999)
error_msg = 'Barnacles!'
mock_umask.side_effect = Exception(error_msg)
mock_os.umask.side_effect = Exception(error_msg)
with self.assertRaisesRegex(exception.DetachProcessError, error_msg):
with utils.detach_process():
@ -199,10 +185,9 @@ class DetachProcessUtilsTestCase(base.TestCase):
# assert fork() has been called twice
expected_fork_calls = [mock.call()] * 2
self.assertEqual(expected_fork_calls, mock_fork.call_args_list)
self.assertEqual(expected_fork_calls, mock_os.fork.call_args_list)
mock_setsid.assert_called_once_with()
mock_chdir.assert_called_once_with('/')
mock__exit.assert_called_once_with(0)
mock_umask.assert_called_once_with(0)
self.assertFalse(mock_getpid.called)
mock_os.setsid.assert_called_once_with()
mock_os.chdir.assert_called_once_with('/')
mock_os._exit.assert_called_once_with(0)
mock_os.umask.assert_called_once_with(0)

36
virtualbmc/utils.py
View File

@ -10,8 +10,10 @@
# License for the specific language governing permissions and limitations
# under the License.
import libvirt
import os
import sys
import libvirt
from virtualbmc import exception
@ -97,12 +99,14 @@ def mask_dict_password(dictionary, secret='***'):
class detach_process(object):
"""Detach the process from its parent and session."""
def _fork(self):
def _fork(self, parent_exits):
try:
ret = os.fork()
if ret > 0:
# Exit the parent process
pid = os.fork()
if pid > 0 and parent_exits:
os._exit(0)
return pid
except OSError as e:
raise exception.DetachProcessError(error=e)
@ -133,13 +137,29 @@ class detach_process(object):
raise exception.DetachProcessError(error=error)
def __enter__(self):
self._fork()
pid = self._fork(parent_exits=False)
if pid > 0:
return pid
os.setsid()
self._fork()
self._fork(parent_exits=True)
self._change_root_directory()
self._change_file_creation_mask()
return os.getpid()
sys.stdout.flush()
sys.stderr.flush()
si = open(os.devnull, 'r')
so = open(os.devnull, 'a+')
se = open(os.devnull, 'a+')
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
return pid
def __exit__(self, type, value, traceback):
pass