New submission from Robert Xiao <[email protected]>:
tempfile.NamedTemporaryFile creates its wrapper like so:
try:
file = _io.open(fd, mode, buffering=buffering,
newline=newline, encoding=encoding, errors=errors)
return _TemporaryFileWrapper(file, name, delete)
except BaseException:
_os.unlink(name)
_os.close(fd)
raise
If _TemporaryFileWrapper throws any kind of exception (even KeyboardInterrupt),
this closes `fd` but leaks a valid `file` pointing to that fd. The `file` will
later attempt to close the `fd` when it is collected, which can lead to subtle
bugs. (This particular issue contributed to this bug:
https://nedbatchelder.com/blog/202001/bug_915_please_help.html)
This should probably be rewritten as:
try:
file = _io.open(fd, mode, buffering=buffering,
newline=newline, encoding=encoding, errors=errors)
except:
_os.unlink(name)
_os.close(fd)
raise
try:
return _TemporaryFileWrapper(file, name, delete)
except BaseException:
_os.unlink(name)
file.close()
raise
or perhaps use nested try blocks to avoid the _os.unlink duplication.
----------
components: Library (Lib)
messages: 359888
nosy: nneonneo
priority: normal
severity: normal
status: open
title: NamedTemporaryFile could cause double-close on an fd if
_TemporaryFileWrapper throws
type: behavior
versions: Python 3.5, Python 3.6, Python 3.7, Python 3.8, Python 3.9
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Python tracker <[email protected]>
<https://bugs.python.org/issue39318>
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