[issue45564] shutil.rmtree and os.walk are implemented using recursion, fail on deep hierarchies

[Alexander Patrakov]

New submission from Alexander Patrakov <patrakov at gmail.com>:

It is possible to create deep directory hierarchies that cannot be removed via shutil.rmtree or walked via os.walk, because these functions exceed the interpreter recursion limit. This may have security implications for web services (e.g. various webdisks) that have to clean up user-created mess or walk through it.

[aep at aep-haswell ~]$ mkdir /tmp/badstuff
[aep at aep-haswell ~]$ cd /tmp/badstuff
[aep at aep-haswell badstuff]$ for x in `seq 2048` ; do mkdir $x ; cd $x ; done
[aep at aep-haswell 103]$ cd
[aep at aep-haswell ~]$ python
Python 3.9.7 (default, Oct 10 2021, 15:13:22) 
[GCC 11.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import shutil
>>> shutil.rmtree('/tmp/badstuff')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.9/shutil.py", line 726, in rmtree
    _rmtree_safe_fd(fd, path, onerror)
  File "/usr/lib/python3.9/shutil.py", line 663, in _rmtree_safe_fd
    _rmtree_safe_fd(dirfd, fullname, onerror)
  File "/usr/lib/python3.9/shutil.py", line 663, in _rmtree_safe_fd
    _rmtree_safe_fd(dirfd, fullname, onerror)
  File "/usr/lib/python3.9/shutil.py", line 663, in _rmtree_safe_fd
    _rmtree_safe_fd(dirfd, fullname, onerror)
  [Previous line repeated 992 more times]
  File "/usr/lib/python3.9/shutil.py", line 642, in _rmtree_safe_fd
    fullname = os.path.join(path, entry.name)
  File "/usr/lib/python3.9/posixpath.py", line 77, in join
    sep = _get_sep(a)
  File "/usr/lib/python3.9/posixpath.py", line 42, in _get_sep
    if isinstance(path, bytes):
RecursionError: maximum recursion depth exceeded while calling a Python object
>>> import os
>>> list(os.walk('/tmp/badstuff'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.9/os.py", line 418, in _walk
    yield from _walk(new_path, topdown, onerror, followlinks)
  File "/usr/lib/python3.9/os.py", line 418, in _walk
    yield from _walk(new_path, topdown, onerror, followlinks)
  File "/usr/lib/python3.9/os.py", line 418, in _walk
    yield from _walk(new_path, topdown, onerror, followlinks)
  [Previous line repeated 993 more times]
  File "/usr/lib/python3.9/os.py", line 412, in _walk
    new_path = join(top, dirname)
  File "/usr/lib/python3.9/posixpath.py", line 77, in join
    sep = _get_sep(a)
  File "/usr/lib/python3.9/posixpath.py", line 42, in _get_sep
    if isinstance(path, bytes):
RecursionError: maximum recursion depth exceeded while calling a Python object
>>>

----------
components: Library (Lib)
messages: 404687
nosy: Alexander.Patrakov
priority: normal
severity: normal
status: open
title: shutil.rmtree and os.walk are implemented using recursion, fail on deep hierarchies
type: crash
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45564>
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