[issue30570] issubclass segfaults on objects with weird __getattr__

[Dennis Sweeney]

Dennis Sweeney  added the comment:

Since this isn't quite related to the original issue, I opened bpo-45806 to 
discuss.

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[issue30570] issubclass segfaults on objects with weird __getattr__

[David Bolen]

David Bolen  added the comment:

So I'm guessing something is just borderline under 3.9 on Windows.

In some manual testing with a standalone build of 3.9 so far for me:
  -m test.test_pickle always succeeds (executed directly)
  -m test test_pickle always fails (executed via test module)
  -m test -w -j1 test_pickle  fails, but succeeds on retry

The failures seem to always occur in CPicklerTests.test_bad_getattr.  I'm not 
sure how to run that single test via the test module, but limiting to all 
CPicklerTests tests or all test_bad_getattr tests succeeds even through the 
test module.

The last scenario above (successful retry) has to use -j or else no retry (-w) 
takes place.  That's the path the buildbots are following.

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[issue30570] issubclass segfaults on objects with weird __getattr__

[David Bolen]

David Bolen  added the comment:

I don't know if this is a buildbot, test or 3.9-specific issue but this commit 
appears to have introduced a permanent initial failure (but success on retry) 
in test_pickle on both Windows 10 3.9 builders.  First failure for my builder 
at https://buildbot.python.org/all/#/builders/425/builds/450

Fatal Python error: _Py_CheckRecursiveCall: Cannot recover from stack overflow.
0:14:47 load avg: 4.57 Re-running failed tests in verbose mode
0:14:47 load avg: 4.57 Re-running test_pickle in verbose mode

The 3.x and 3.10 builders seem fine, and the second try on 3.9 always seems to 
succeed (perhaps because it's just a single test running at that point), so 
this is only being reported as a buildbot warning.

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nosy: +db3l

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Łukasz Langa]

Łukasz Langa  added the comment:

Thanks, Dennis! ✨ 🍰 ✨

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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Łukasz Langa]

Łukasz Langa  added the comment:


New changeset f701237db2611140e578cebbdfef91ae4714af4e by Łukasz Langa in 
branch '3.9':
[3.9] bpo-30570: Fix segfault on buildbots caused by stack overflow from 
recursion in tests (GH-29258) (GH-29415)
https://github.com/python/cpython/commit/f701237db2611140e578cebbdfef91ae4714af4e


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[issue30570] issubclass segfaults on objects with weird __getattr__

[miss-islington]

miss-islington  added the comment:


New changeset 1f3ae5c1ca5a8e7696bad414c1de38e0f5f1e2c3 by Miss Islington (bot) 
in branch '3.10':
bpo-30570: Fix segfault on buildbots caused by stack overflow from recursion in 
tests (GH-29258)
https://github.com/python/cpython/commit/1f3ae5c1ca5a8e7696bad414c1de38e0f5f1e2c3


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[issue30570] issubclass segfaults on objects with weird __getattr__

[Łukasz Langa]

Change by Łukasz Langa :


--
pull_requests: +27667
pull_request: https://github.com/python/cpython/pull/29415

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Łukasz Langa]

Łukasz Langa  added the comment:


New changeset 1e29dce1138a39e095ba47ab4c1e445fd08716e2 by Miss Islington (bot) 
in branch '3.9':
bpo-30570: Use Py_EnterRecursiveCall() in issubclass() (GH-29048) (GH-29178)
https://github.com/python/cpython/commit/1e29dce1138a39e095ba47ab4c1e445fd08716e2


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[issue30570] issubclass segfaults on objects with weird __getattr__

[miss-islington]

Change by miss-islington :


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pull_requests: +27666
pull_request: https://github.com/python/cpython/pull/29414

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:


New changeset d56375a0dd4cee162081b173310298a3d32af293 by Dennis Sweeney in 
branch 'main':
bpo-30570: Fix segfault on buildbots caused by stack overflow from recursion in 
tests (GH-29258)
https://github.com/python/cpython/commit/d56375a0dd4cee162081b173310298a3d32af293


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[issue30570] issubclass segfaults on objects with weird __getattr__

[Dennis Sweeney]

Dennis Sweeney  added the comment:

I think this broke some buildbots.

https://buildbot.python.org/all/#/builders/256/builds/264
https://buildbot.python.org/all/#/builders/370/builds/263

I opened a PR to temporarily decrease the recursion limit so that the C stack 
doesn't overflow in these new test.

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Dennis Sweeney]

Change by Dennis Sweeney :


--
pull_requests: +27522
pull_request: https://github.com/python/cpython/pull/29258

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[issue30570] issubclass segfaults on objects with weird __getattr__

[miss-islington]

Change by miss-islington :


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pull_requests: +27451
pull_request: https://github.com/python/cpython/pull/29178

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[issue30570] issubclass segfaults on objects with weird __getattr__

[miss-islington]

miss-islington  added the comment:


New changeset f812fef2f8f12441ce559335645433c8124e7db5 by Miss Islington (bot) 
in branch '3.10':
bpo-30570: Use Py_EnterRecursiveCall() in issubclass() (GH-29048)
https://github.com/python/cpython/commit/f812fef2f8f12441ce559335645433c8124e7db5


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[issue30570] issubclass segfaults on objects with weird __getattr__

[Gregory P. Smith]

Gregory P. Smith  added the comment:


New changeset 423fa1c1817abfa8c3d1bc308ddbbd8f28b69d68 by Dennis Sweeney in 
branch 'main':
bpo-30570: Use Py_EnterRecursiveCall() in issubclass() (GH-29048)
https://github.com/python/cpython/commit/423fa1c1817abfa8c3d1bc308ddbbd8f28b69d68


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[issue30570] issubclass segfaults on objects with weird __getattr__

[miss-islington]

Change by miss-islington :


--
nosy: +miss-islington
nosy_count: 10.0 -> 11.0
pull_requests: +27448
pull_request: https://github.com/python/cpython/pull/29175

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Dennis Sweeney]

Change by Dennis Sweeney :


--
pull_requests: +27319
pull_request: https://github.com/python/cpython/pull/29048

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Dennis Sweeney]

Dennis Sweeney  added the comment:

Oh yeah -- Py_EnterRecursiveCall/Py_LeaveRecursiveCall in abstract_get_bases 
would be simpler. Also, the set approach also probably still c-stack overflows 
on

class C:
def __getattr__(self, attr):
class A: pass
class B: pass
A.__getattr__ = B.__getattr__ = C.__getattr__
return (A(), B())

issubclass(C(), int)

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Carl Friedrich Bolz-Tereick]

Carl Friedrich Bolz-Tereick  added the comment:

PyPy raises a RecursionError here, which sounds like an ok outcome. So simply 
checking for the recursion would also be a way of fixing this...

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Gregory P. Smith]

Change by Gregory P. Smith :


--
keywords: +patch
pull_requests: +27291
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/29017

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Gregory P. Smith]

Gregory P. Smith  added the comment:

Python metaprogramming allows type-like things to be bases, not just things 
that pass PyType_Check().  so being that strict isn't going to work.

The other classic way to prevent this is to track what you're recursing on to 
avoid a loop.  i.e. Keeping a set of PyObjects that have been seen and not 
recursing if the value is in that.

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Gregory P. Smith]

Change by Gregory P. Smith :


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assignee:  -> gregory.p.smith

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Gregory P. Smith]

Gregory P. Smith  added the comment:

This is a stack overflow in Objects/abstract.c because we infinitely recurse 
within abstract_issubclass().

We should probably do some validity checking on the bases tuple that 
abstract_get_bases returns (ideally within abstract_get_bases?).  The tuple 
must contain types.

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nosy: +gregory.p.smith

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Irit Katriel]

Irit Katriel  added the comment:

Reproduced on 3.11.

--
nosy: +iritkatriel
versions: +Python 3.10, Python 3.11, Python 3.9 -Python 2.7, Python 3.5, Python 
3.6, Python 3.7

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Jim Fasarakis-Hilliard]

Changes by Jim Fasarakis-Hilliard :


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nosy: +Jim Fasarakis-Hilliard

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

This looks as yet one example of issues similar of issue14010.

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nosy: +serhiy.storchaka

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[issue30570] issubclass segfaults on objects with weird __getattr__

[R. David Murray]

R. David Murray added the comment:

Yes, but we try to make it not possible to segfault the interpreter with pure 
python code that isn't intentionally mucking with C-level stuff, so this is a 
bug we would like to fix.

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nosy: +r.david.murray

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Louie Lu]

Louie Lu added the comment:

Without this segfault, I think you do a wrong operation. In other cases, for 
example:

>>> issubclass(10, int)
Traceback (most recent call last):
  File "", line 1, in 
TypeError: issubclass() arg 1 must be a class


`issubclass` will return TypeError on instance, if you test as 
`issubclass(Failure, int)` or `issubclass(Failure().__class__, int`, it should 
get the correct answer.

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Louie Lu]

Louie Lu added the comment:

I can reproduce this bugs on 3.7, Linux.

Python 3.7.0a0 (heads/master:d3bedf356a, Jun  5 2017, 10:21:52) 
[GCC 6.3.1 20170306] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> class Foo(object):
...  def __getattr__(self, attr):
...   return (self, None)
... 
>>> issubclass(Foo(), int)

[1]21897 segmentation fault (core dumped)  ./python

--
nosy: +louielu
versions: +Python 3.7

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Bruno Oliveira]

Changes by Bruno Oliveira :


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nosy: +Bruno Oliveira

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Daniel Lepage]

Daniel Lepage added the comment:

I tried it on python 2.7.12 and python 2.6.9 since I had them lying around and 
got the same behavior.

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Daniel Lepage]

New submission from Daniel Lepage:

The following code causes a segmentation fault:
class Failure(object):
def __getattr__(self, attr):
return (self, None)
issubclass(Failure(), int)

I am running a macbook pro, OS X 10.12.4, and have observed the problem in 
python 3.5.2, 3.6.0, and 3.6.1.

It appears that returning (self,) causes it to go into an infinite loop 
attempting to get `x.__bases__`, and returning `(self, y)` for any value `y` 
causes it to attempt to get `x.__bases__` 262,030 times and then segfault.

A crash log is attached.

--
components: Interpreter Core
files: segfault.crash
messages: 295150
nosy: Daniel Lepage
priority: normal
severity: normal
status: open
title: issubclass segfaults on objects with weird __getattr__
type: crash
versions: Python 3.5, Python 3.6
Added file: http://bugs.python.org/file46924/segfault.crash

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[issue30570] issubclass segfaults on objects with weird __getattr__

[Daniel Lepage]

Changes by Daniel Lepage :


--
versions: +Python 2.7

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