New submission from Alexey Izbyshev <izbys...@ispras.ru>:
Demo:
>>> import os
>>> os.chdir(-1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OSError: [Errno 14] Bad address: -1
>>> os.chdir(-2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OSError: [Errno 9] Bad file descriptor: -2
Functions in os supporting either path or file descriptor argument
(os.supports_fd) usually use the following code pattern to distinguish between
those cases:
if (path->fd != -1)
result = fchdir(path->fd);
else
result = chdir(path->narrow);
However, _fd_converter used by path_converter internally doesn't give any
special meaning to -1 and allows any negative file descriptors. Therefore, if a
user passes -1 to such function, path->narrow, which is NULL, will be used.
I see two ways to fix this.
1) Make some flag in path_t indicating that it should be treated as fd and make
all users check that flag.
2) Make _fd_converter raise an exception for negative descriptors.
Also, I have to mention an inconsistency in reporting of bad descriptors. A
handful of os functions uses fildes_converter for descriptors, which uses
PyObject_AsFileDescriptor, which in turn is used in other places in Python as
well (e.g. in fcntl module). PyObject_AsFileDescriptor raises a ValueError for
negative descriptors instead of OSError raised by most os functions in this
case.
>>> os.fchdir(-1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: file descriptor cannot be a negative integer (-1)
----------
messages: 312421
nosy: izbyshev
priority: normal
severity: normal
status: open
title: os: Users of path_converter don't handle fd == -1 properly
type: behavior
versions: Python 3.6, Python 3.7
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue32887>
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