gh-97591: In Exception.__setstate__(), acquire strong reference before calling tp_hash slot.

[ofey404]

Added an Py_INCREF / Py_DECREF pair around the call of tp_hash slot in Exception.__setstate__().

If the last reference of dict value is cleared (by dict.clear()), during the __setstate__ method call, it would cause gc crash.

A script to reproduce this is in #97591 :

import gc

class Key(str):
    def __hash__(self):
        d.clear()
        return 0

class Value(str):
    pass

d = {}
d[Key()] = Value()

e = Exception()
e.__setstate__(d)

gc.collect() # Segfault happens here

Similiar issue: #92930

• Issue: Setting state of an exception object with a dic crashes Python 3.8.14  #97591

[gvanrossum]

LG, I just think you could add your name to the NEWS item.

[ofey404]

@kumaraditya303 I notice the “back port to 3.10/11” tag, and I wonder how to do the back port? If it’s proper I’d like to do it.

[gvanrossum]

LGTM.

Regarding the backport, this is usually taken care of automatically by the Miss-Islington bot. Only if there are git merge problems the bot can't do it, a manual backport is required. In that case you're welcome to try it.

[miss-islington]

Thanks @ofey404 for the PR, and @gvanrossum for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11.
🐍🍒⛏🤖

[bedevere-bot]

GH-97716 is a backport of this pull request to the 3.11 branch.

[bedevere-bot]

GH-97717 is a backport of this pull request to the 3.10 branch.

[gvanrossum]

You're lucky, the backports happened automatically. They'll be merged as soon as the tests pass (since I pre-approved them).