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jwilk opened this issue Dec 19, 2024 · 5 comments
Open

os.path.realpath() RecursionError #128098

jwilk opened this issue Dec 19, 2024 · 5 comments
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3.12 only security fixes 3.13 bugs and security fixes 3.14 bugs and security fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error

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@jwilk
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jwilk commented Dec 19, 2024 •
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os.path.realpath() attempts to detect symlink loops, but this is not bulletproof;
it's possible to make it fall into infinite recursion.

Reproducer:

import os
import tempfile

with tempfile.TemporaryDirectory() as tmpdir:
    os.chdir(tmpdir)
    os.symlink('../' * (1 + tmpdir.count('/')) + f'{tmpdir}/d', 'd')
    os.path.realpath('d')

Traceback:

Traceback (most recent call last):
  File ".../recursiverealpath.py", line 7, in <module>
    os.path.realpath('d')
  File "<frozen posixpath>", line 427, in realpath
  File "<frozen posixpath>", line 487, in _joinrealpath
  File "<frozen posixpath>", line 487, in _joinrealpath
  File "<frozen posixpath>", line 487, in _joinrealpath
  [Previous line repeated 993 more times]
  File "<frozen posixpath>", line 442, in _joinrealpath
  File "<frozen posixpath>", line 63, in isabs
RecursionError: maximum recursion depth exceeded

Tested with Python 3.12.8.
@picnixz picnixz added extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error 3.12 only security fixes 3.13 bugs and security fixes 3.14 bugs and security fixes labels Dec 20, 2024
@keainye
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keainye commented Jan 7, 2025 •
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This issue no longer reproduces in the the latest version (Python 3.14.0a3+ (heads/main:f802c8bf87, Jan 7 2025, 08:12:30) [GCC 12.2.0] on linux).

And in my opinion it seems to be an issue with os.symlink as it doesn't handle illegal paths...

@jwilk
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jwilk commented Jan 7, 2025

This issue no longer reproduces in the the latest version

Looks like this was indeed fixed in abfa16b ("GH-114847: Speed up posixpath.realpath() (#114848)").

in my opinion it seems to be an issue with os.symlink as it doesn't handle illegal paths...

No, os.symlink() works as expected.

@picnixz
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picnixz commented Feb 8, 2025

@barneygale Should we backport gh-114848 to fix the issue or is there something else we should do for 3.12 and 3.13?

@barneygale
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I think #114848 landed in 3.13 already? Not sure about backporting to 3.12 - it's close to EOL and the fix is invasive

@picnixz
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picnixz commented Feb 8, 2025

Ok, yes indeed it landed in 3.13.0a6. I think we can close this one as wont fix for 3.12 and completed for 3.13+.

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3.12 only security fixes 3.13 bugs and security fixes 3.14 bugs and security fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error
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