New submission from Samson Lee:
The bug is os.fwalk() crashes with unhandled exception when there is an error
accessing symbolic link targets.
To reproduce the bug, create a symbolic link that targets a file that you do not
have permission to access:
$ touch handsoff
$ sudo chown root:root handsoff
$ sudo chmod 700 handsoff
$ ln -s handsoff blah
Now, os.fwalk() fails:
>>> for root, dirs, files, fd in os.fwalk('.'):
... print(root, dirs, files)
...
Traceback (most recent call last):
File "test_fwalk_permission_error.py", line 3, in <module>
for root, dirs, files, fd in os.fwalk('.'):
File "/usr/lib64/python3.5/os.py", line 520, in fwalk
yield from _fwalk(topfd, top, topdown, onerror, follow_symlinks)
File "/usr/lib64/python3.5/os.py", line 537, in _fwalk
if st.S_ISDIR(stat(name, dir_fd=topfd).st_mode):
PermissionError: [Errno 13] Permission denied: 'blah'
The cause of the problem is in this part of os.py:
for name in names:
try:
# Here, we don't use AT_SYMLINK_NOFOLLOW to be consistent with
# walk() which reports symlinks to directories as directories.
# We do however check for symlinks before recursing into
# a subdirectory.
if st.S_ISDIR(stat(name, dir_fd=topfd).st_mode):
dirs.append(name)
else:
nondirs.append(name)
except FileNotFoundError:
try:
# Add dangling symlinks, ignore disappeared files
if st.S_ISLNK(stat(name, dir_fd=topfd, follow_symlinks=False)
.st_mode):
nondirs.append(name)
except FileNotFoundError:
continue
To fix it, simply replace FileNotFoundError with more general OSError.
Cheers
----------
components: Library (Lib)
messages: 278016
nosy: Samson Lee
priority: normal
severity: normal
status: open
title: os.fwalk() unhandled exception when error occurs accessing symbolic link
target
versions: Python 3.5, Python 3.6
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue28353>
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