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qubes: add filename= argument to Qubes.save()

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fixes QubesOS/qubes-issues#1846
This commit is contained in:
Wojtek Porczyk 2016-05-05 00:40:45 +02:00
parent 1d5b89f0d5
commit f8270a07bb
1 changed files with 13 additions and 7 deletions
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20
qubes/__init__.py
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@ -1336,9 +1336,12 @@ class Qubes(PropertyHolder):
return element
def save(self):
def save(self, filename=None):
'''Save all data to qubes.xml
:param str filename: optional filename, if other than the one from \
which the store was loaded
There are several problems with saving :file:`qubes.xml` which must be
mitigated:
@ -1350,8 +1353,11 @@ class Qubes(PropertyHolder):
:throws EnvironmentError: failure on saving
'''
if filename is None:
filename = self._store
while True:
fd_old = os.open(self._store, os.O_RDWR | os.O_CREAT)
fd_old = os.open(filename, os.O_RDWR | os.O_CREAT)
if os.name == 'posix':
fcntl.lockf(fd_old, fcntl.LOCK_EX)
elif os.name == 'nt':
@ -1364,32 +1370,32 @@ class Qubes(PropertyHolder):
# While we were waiting for lock, someone could have unlink()ed (or
# rename()d) our file out of the filesystem. We have to ensure we
# got lock on something linked to filesystem. If not, try again.
if os.fstat(fd_old) == os.stat(self._store):
if os.fstat(fd_old) == os.stat(filename):
break
else:
os.close(fd_old)
if self.__load_timestamp:
current_file_timestamp = os.path.getmtime(self._store)
current_file_timestamp = os.path.getmtime(filename)
if current_file_timestamp != self.__load_timestamp:
os.close(fd_old)
raise qubes.exc.QubesException(
"Someone else modified qubes.xml in the meantime")
fh_new = tempfile.NamedTemporaryFile(prefix=self._store, delete=False)
fh_new = tempfile.NamedTemporaryFile(prefix=filename, delete=False)
lxml.etree.ElementTree(self.__xml__()).write(
fh_new, encoding='utf-8', pretty_print=True)
fh_new.flush()
os.chmod(fh_new.name, 0660)
os.chown(fh_new.name, -1, grp.getgrnam('qubes').gr_gid)
os.rename(fh_new.name, self._store)
os.rename(fh_new.name, filename)
# intentionally do not call explicit unlock to not unlock the file
# before all buffers are flushed
fh_new.close()
# update stored mtime, in case of multiple save() calls without
# loading qubes.xml again
self.__load_timestamp = os.path.getmtime(self._store)
self.__load_timestamp = os.path.getmtime(filename)
os.close(fd_old)