[New-bugs-announce] [issue28129] assertion failures in ctypes

[Oren Milman]

New submission from Oren Milman:

------------ current state ------------
In Modules\_ctypes\_ctypes.c, there are six functions with assertions that might fail:
    1. CDataType_from_buffer
    2. CDataType_from_buffer_copy
    3. PyCPointerType_set_type
    4. PyCPointerType_from_param
    5. PyCSimpleType_from_param
    6. _validate_paramflags
The following is true for each of these functions:
    - It assumes its first argument is a subclass (or an instance of a subclass) of some abstract ctype, which means it (the first argument) has a storage dict.
    - Thus, it asserts its first argument has a storage dict.
    - However, its first argument might be some abstract ctype (and not a subclass (or an instance of a subclass) of that abstract ctype), in which case the assertion fails.

In Modules\_ctypes\cfield.c, there are two functions with assertions that might fail:
    1. PyCField_set
    2. PyCField_get
These functions are the C implementations of the __set__ and __get__ functions (respectively) of the CFeild type. Each of them asserts its instance argument is a CDataObject, which might not be true.


------------ proposed changes ------------
Replace each of these assertions with an if statement that raises an exception in case of an invalid argument.


------------ diff ------------
The proposed patches diff file is attached.


------------ tests ------------
I wrote an ugly script to verify the assertion failures on CPython without my patches, and to test the patches on CPython with my patches. The script is attached, but it would probably fail on a non-Windows machine.

I built the patched CPython for x86, and played with it a little. Everything seemed to work as usual.

In addition, I ran 'python_d.exe -m test -j3' (on my 64-bit Windows 10) with and without the patches, and got quite the same output.
The outputs of both runs are attached.

----------
components: ctypes
files: testBugsOrPatches.py
messages: 276288
nosy: Oren Milman
priority: normal
severity: normal
status: open
title: assertion failures in ctypes
type: crash
versions: Python 3.7
Added file: http://bugs.python.org/file44636/testBugsOrPatches.py

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28129>
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