gh-157265: Honor None result of filter for link fallbacks by encukou · Pull Request #157266 · python/cpython

encukou · 2026-09-10T11:48:20Z

Issue: tarfile hardlink fallback ignores custom extraction filter rejection via None #157265

Co-authored-by: Stan Ulbrych <stan@python.org>

miss-islington-app · 2026-09-11T12:20:19Z

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10.
🐍🍒⛏🤖

miss-islington-app · 2026-09-11T12:20:19Z

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

miss-islington-app · 2026-09-11T12:20:19Z

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

miss-islington-app · 2026-09-11T12:20:20Z

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

miss-islington-app · 2026-09-11T12:20:20Z

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

miss-islington-app · 2026-09-11T12:20:20Z

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

bedevere-app · 2026-09-11T12:20:38Z

GH-157304 is a backport of this pull request to the 3.10 branch.

bedevere-app · 2026-09-11T12:20:45Z

GH-157305 is a backport of this pull request to the 3.12 branch.

bedevere-app · 2026-09-11T12:20:49Z

GH-157306 is a backport of this pull request to the 3.11 branch.

bedevere-app · 2026-09-11T12:20:56Z

GH-157307 is a backport of this pull request to the 3.14 branch.

bedevere-app · 2026-09-11T12:21:01Z

GH-157308 is a backport of this pull request to the 3.13 branch.

bedevere-app · 2026-09-11T12:21:19Z

GH-157309 is a backport of this pull request to the 3.15 branch.

bedevere-bot · 2026-09-11T12:41:48Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Debian root 3.x (tier-1) has failed when building commit fb2f0bb.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/345/builds/15324) and take a look at the build logs.
Check if the failure is related to this commit (fb2f0bb) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/345/builds/15324

Failed tests:

test.test_multiprocessing_fork.test_processes

Failed subtests:

test_interrupt - test.test_multiprocessing_fork.test_processes.WithProcessesTestProcess.test_interrupt

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/contextlib.py", line 116, in inner
    return func(*args, **kwds)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 651, in test_interrupt
    exitcode = self._kill_process(multiprocessing.Process.interrupt)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/contextlib.py", line 116, in inner
    return func(*args, **kwds)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 632, in _kill_process
    self.assertEqual(join(), None)
                     ~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 305, in __call__
    return self.func(*args, **kwds)
           ~~~~~~~~~^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 156, in join
    res = self._popen.wait(timeout)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 44, in wait
    return self.poll(os.WNOHANG if timeout == 0.0 else 0)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 28, in poll
    pid, sts = os.waitpid(self.pid, flag)
               ~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 628, in handler
    raise RuntimeError('join took too long: %s' % p)
RuntimeError: join took too long: <Process name='Process-1' pid=3460618 parent=3460616 started daemon>


Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/contextlib.py", line 116, in inner
    return func(*args, **kwds)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 651, in test_interrupt
    exitcode = self._kill_process(multiprocessing.Process.interrupt)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/contextlib.py", line 116, in inner
    return func(*args, **kwds)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 632, in _kill_process
    self.assertEqual(join(), None)
                     ~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 305, in __call__
    return self.func(*args, **kwds)
           ~~~~~~~~~^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 156, in join
    res = self._popen.wait(timeout)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 44, in wait
    return self.poll(os.WNOHANG if timeout == 0.0 else 0)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 28, in poll
    pid, sts = os.waitpid(self.pid, flag)
               ~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 628, in handler
    raise RuntimeError('join took too long: %s' % p)
RuntimeError: join took too long: <Process name='Process-171' pid=3439307 parent=3438815 started daemon>

bedevere-bot · 2026-09-11T12:42:54Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 Windows 3.x (tier-2) has failed when building commit fb2f0bb.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/729/builds/11241) and take a look at the build logs.
Check if the failure is related to this commit (fb2f0bb) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/729/builds/11241

Failed tests:

test_tarfile

Failed subtests:

test_sneaky_hardlink_fallback - test.test_tarfile.TestExtractionFilters.test_sneaky_hardlink_fallback

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "C:\Users\buildworker\buildarea\3.x.ware-win11-arm64\build\Lib\test\test_tarfile.py", line 4625, in test_sneaky_hardlink_fallback
    self.expect_exception(
    ~~~~~~~~~~~~~~~~~~~~~^
        tarfile.LinkFallbackError,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
        "link 'boom' would be extracted as a copy of "
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        + "'c/escape', which was rejected")
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\buildworker\buildarea\3.x.ware-win11-arm64\build\Lib\test\test_tarfile.py", line 4099, in expect_exception
    with self.assertRaisesRegex(exc_type, message_re):
         ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
AssertionError: LinkFallbackError not raised

bedevere-bot · 2026-09-11T12:54:31Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows11 Non-Debug 3.x (tier-1) has failed when building commit fb2f0bb.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/914/builds/6095) and take a look at the build logs.
Check if the failure is related to this commit (fb2f0bb) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/914/builds/6095

Failed tests:

test_tarfile

Failed subtests:

test_sneaky_hardlink_fallback - test.test_tarfile.TestExtractionFilters.test_sneaky_hardlink_fallback

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "b:\uildarea\3.x.ware-win11.nondebug\build\Lib\test\test_tarfile.py", line 4625, in test_sneaky_hardlink_fallback
    self.expect_exception(
    ~~~~~~~~~~~~~~~~~~~~~^
        tarfile.LinkFallbackError,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
        "link 'boom' would be extracted as a copy of "
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        + "'c/escape', which was rejected")
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "b:\uildarea\3.x.ware-win11.nondebug\build\Lib\test\test_tarfile.py", line 4099, in expect_exception
    with self.assertRaisesRegex(exc_type, message_re):
         ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
AssertionError: LinkFallbackError not raised

gh-157266: Adjust test for Windows On Windows (no symlinks, no hardlinks), the behaviour is the same as without the fix in GH-157266: - a/t/dummy is extracted - b/ is extracted - c/ is *not* created (the target, a/t, is not in the archive) - c/escape: c/ is created; escape is skipped (target, c/../../link_here, is not in archive) - c is not recreated as a directory - boom is not created (target is c/escape, which falls back to ..\..\link_here, which does not exist in archive)

…cks (pythonGH-157266) Co-authored-by: Stan Ulbrych <stan@python.org>

pythongh-157266: Adjust test for Windows On Windows (no symlinks, no hardlinks), the behaviour is the same as without the fix in pythonGH-157266: - a/t/dummy is extracted - b/ is extracted - c/ is *not* created (the target, a/t, is not in the archive) - c/escape: c/ is created; escape is skipped (target, c/../../link_here, is not in archive) - c is not recreated as a directory - boom is not created (target is c/escape, which falls back to ..\..\link_here, which does not exist in archive)

encukou and others added 3 commits September 10, 2026 13:39

Honor None result of filter for link fallbacks

3d66a90

Apply review suggestions

5c3e146

Co-authored-by: Stan Ulbrych <stan@python.org>

Add NEWS file

aebd409

encukou requested a review from ethanfurman as a code owner September 10, 2026 11:48

bedevere-app Bot mentioned this pull request Sep 10, 2026

tarfile hardlink fallback ignores custom extraction filter rejection via None #157265

Open

bedevere-app Bot added the awaiting core review label Sep 10, 2026

StanFromIreland approved these changes Sep 10, 2026

View reviewed changes

bedevere-app Bot added awaiting merge and removed awaiting core review labels Sep 10, 2026

encukou merged commit fb2f0bb into python:main Sep 11, 2026
60 checks passed

bedevere-app Bot removed the awaiting merge label Sep 11, 2026

encukou deleted the tarfile-hardlink-none branch September 11, 2026 12:19

bedevere-app Bot removed the needs backport to 3.10 only security fixes label Sep 11, 2026

bedevere-app Bot removed the needs backport to 3.12 only security fixes label Sep 11, 2026

bedevere-app Bot removed the needs backport to 3.11 only security fixes label Sep 11, 2026

bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Sep 11, 2026

bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label Sep 11, 2026

bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label Sep 11, 2026

encukou mentioned this pull request Sep 11, 2026

gh-157265: Adjust test for Windows #157334

Merged

clin1234 pushed a commit to clin1234/cpython that referenced this pull request Sep 12, 2026

pythongh-157265: tarfile: Honor None result of filter for link fallba…

4cbdc6a

…cks (pythonGH-157266) Co-authored-by: Stan Ulbrych <stan@python.org>

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encukou commented Sep 10, 2026 •

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