Change shutil.rmtree and os.walk to support very deep hierarchies

[AlexanderPatrakov]

BPO	45564

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-10-21.22:21:02.146>
labels = ['library', '3.9', 'type-crash']
title = 'shutil.rmtree and os.walk are implemented using recursion, fail on deep hierarchies'
updated_at = <Date 2021-10-21.22:21:02.146>
user = 'https://bugs.python.org/AlexanderPatrakov'

bugs.python.org fields:

activity = <Date 2021-10-21.22:21:02.146>
actor = 'Alexander.Patrakov'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-10-21.22:21:02.146>
creator = 'Alexander.Patrakov'
dependencies = []
files = []
hgrepos = []
issue_num = 45564
keywords = []
message_count = 1.0
messages = ['404687']
nosy_count = 1.0
nosy_names = ['Alexander.Patrakov']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue45564'
versions = ['Python 3.9']

Linked PRs

• gh-89727: Fix os.walk RecursionError on deep trees #99803
• gh-89727: Fix pathlib.Path.walk RecursionError on deep trees #100282
• gh-89727: Fix os.fwalk RecursionError on deep trees #100347
• gh-89727: Improve os.walk complexity and speed #100671
• gh-89727: Fix os.walk to handle late editing of dirs #100703
• [WIP] GH-89727: Fix shutil.rmtree() recursion error on deep trees. #103164
• gh-89727: add os.walkdir and os.fwalkdir #103234
• GH-89727: Add pathlib.Path.fwalk() method #103566
• GH-89727: Partially fix shutil.rmtree() recursion error on deep trees #119634
• GH-89727: Fix os.fwalk() recursion error on deep trees #119638
• [3.13] GH-89727: Partially fix shutil.rmtree() recursion error on deep trees (GH-119634) #119748
• [3.12] GH-89727: Partially fix shutil.rmtree() recursion error on deep trees (GH-119634) #119749
• [3.13] GH-89727: Fix os.fwalk() recursion error on deep trees (GH-119638) #119764
• [3.12] GH-89727: Fix os.fwalk() recursion error on deep trees (GH-119638) #119765
• GH-89727: Fix FD leak on os.fwalk() generator finalization. #119766
• [3.13] GH-89727: Fix FD leak on os.fwalk() generator finalization. (GH-119766) #119767
• [3.12] GH-89727: Fix FD leak on os.fwalk() generator finalization. (GH-119766) #119768
• GH-89727: Fix shutil.rmtree() recursion error on deep trees #119808
• [3.13] GH-89727: Fix shutil.rmtree() recursion error on deep trees (GH-119808) #119918
• [3.12] GH-89727: Fix shutil.rmtree() recursion error on deep trees (GH-119808) #119919

[AlexanderPatrakov]

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@aep-haswell ~]$ mkdir /tmp/badstuff
[aep@aep-haswell ~]$ cd /tmp/badstuff
[aep@aep-haswell badstuff]$ for x in `seq 2048` ; do mkdir $x ; cd $x ; done
[aep@aep-haswell 103]$ cd
[aep@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
>>>

[barneygale]

This also affects pathlib.Path.walk()