[issue34697] ctypes: Crash if manually-created CField instance is used

[Irit Katriel]

Change by Irit Katriel :


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versions: +Python 3.10, Python 3.11, Python 3.9 -Python 2.7, Python 3.6, Python 
3.7, Python 3.8

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[issue34697] ctypes: Crash if manually-created CField instance is used

[hai shi]

hai shi  added the comment:

ping

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[issue34697] ctypes: Crash if manually-created CField instance is used

[hai shi]

hai shi  added the comment:

I have try to cancel this PyCField_new function, but i am not sure I haven't 
break the code structure.

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nosy: +shihai1991

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[issue34697] ctypes: Crash if manually-created CField instance is used

[hai shi]

Change by hai shi :


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keywords: +patch
pull_requests: +14628
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/14837

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[issue34697] ctypes: Crash if manually-created CField instance is used

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

> Is this issue worth fixing?

Definitely yes.

> If so, is the correct way to set tp_new slot to NULL and fix the internal 
> callers so that users wouldn't be able to create CField instances?

I think yes.

Do you mind to create a PR?

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[issue34697] ctypes: Crash if manually-created CField instance is used

[hai shi]

Change by hai shi :


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nosy:  -shihai1991

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[issue34697] ctypes: Crash if manually-created CField instance is used

[hai shi]

Change by hai shi :


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nosy: +shihai1991

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[issue34697] ctypes: Crash if manually-created CField instance is used

[Karthikeyan Singaravelan]

Change by Karthikeyan Singaravelan :


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nosy: +xtreak

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[issue34697] ctypes: Crash if manually-created CField instance is used

[Alexey Izbyshev]

New submission from Alexey Izbyshev :

It is possible to manually create an instance of private CField type which is 
used by ctypes to represent fields of Structure and Union types. This instance 
will be uninitialized because it's normally initialized when instances of 
Structure/Union are created, so calling its methods may crash the interpreter:

from ctypes import *

class S(Structure):
_fields_ = [('x', c_int)]

CField = type(S.x)
f = CField()
repr(f) # Crash here

Is this issue worth fixing?

If so, is the correct way to set tp_new slot to NULL and fix the internal 
callers so that users wouldn't be able to create CField instances?

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components: ctypes
messages: 325448
nosy: amaury.forgeotdarc, belopolsky, berker.peksag, izbyshev, meador.inge, 
serhiy.storchaka
priority: normal
severity: normal
status: open
title: ctypes: Crash if manually-created CField instance is used
type: crash
versions: Python 2.7, Python 3.6, Python 3.7, Python 3.8

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