Segmentation fault in python protobufs when assigning the wrong message type

[gwenwahl]

What version of protobuf and what language are you using?
Version: 4.22.1
Language: Python

What operating system (Linux, Windows, ...) and version?
Appears in MacOS as well as Debian based linux, seems to be platform independent

What runtime / compiler are you using (e.g., python version or gcc version)
Python 3.10.5

What did you do?
If you set the value of a protobuf Message field, that is itself a Message field, to the wrong type of message, this will cause a segmentation fault in python.

An example using included well known types:

Installed packages

-> pip list
Package    Version
---------- -------
pip        22.0.4
protobuf   4.22.1
setuptools 58.1.0

-> python
Python 3.10.5 (main, Jun 28 2022, 11:18:23) [Clang 13.1.6 (clang-1316.0.21.2.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from google.protobuf import api_pb2
>>> api_pb2.Api(source_context=api_pb2.Mixin())
[1]    61055 segmentation fault  python

What did you expect to see
I would expect to get an illegal argument exception or something, instead of a seg fault.

What did you see instead?
A segmentation fault

Make sure you include information that can help us debug (full error message, exception listing, stack trace, logs).

Anything else we should know about your project / environment

[anandolee]

I got TypeError instead:

$ python
Python 3.10.9 (main, Dec  7 2022, 13:47:07) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from google.protobuf import api_pb2
>>> api_pb2.Api(source_context=api_pb2.Mixin())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Parameter to MergeFrom() must be instance of same class: expected google.protobuf.SourceContext got google.protobuf.Mixin.

Verified for pure python, c++ extension and upb

[gwenwahl]

Interesting. I was wondering if it was pyenv installed python, but I'm able to get the segfault even using the default python docker images. Using python:3.10:

➜ docker run --rm -it python:3.10 /bin/bash
root@32356e7b61ca:/# pip install protobuf
Collecting protobuf
  Downloading protobuf-4.22.3-cp37-abi3-manylinux2014_x86_64.whl (302 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 302.4/302.4 kB 5.5 MB/s eta 0:00:00
Installing collected packages: protobuf
Successfully installed protobuf-4.22.3
WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv

[notice] A new release of pip is available: 23.0.1 -> 23.1
[notice] To update, run: pip install --upgrade pip
root@32356e7b61ca:/# python
Python 3.10.11 (main, Apr 12 2023, 14:46:22) [GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from google.protobuf import api_pb2
>>> api_pb2.Api(source_context=api_pb2.Mixin())
Segmentation fault (core dumped)

[freider]

I have the same issue (segfault), using protobuf-4.22.3-cp37-abi3-manylinux2014_x86_64.whl and Python 3.10.8 as well as 3.11.1, if that's any help.

>>> from google.protobuf import api_pb2
>>> api_pb2.Api(source_context=api_pb2.Mixin())
fish: “python” terminated by signal SIGSEGV (Address boundary error)

[nmariz]

This issue is limiting us (MySQL Connector/Python) to add support for 4.22.x. The issue is only observable using >=4.22.0.

[anandolee]

Thank you everyone to make it clear that the Segmentation fault happens for 4.22.x

I verified that

$ pip install protobuf --upgrade
$ pip list
pip                         22.3.1
protobuf                    4.22.3
...
$ python
Python 3.10.9 (main, Dec  7 2022, 13:47:07) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from google.protobuf import api_pb2
>>> api_pb2.Api(source_context=api_pb2.Mixin())
Segmentation fault

This issue will be resolved in our new release of 4.23.X:

$ pip install protobuf --upgrade --pre
$ pip list
pip                         22.3.1
protobuf                    4.23.0rc2
...
$ python
Python 3.10.9 (main, Dec  7 2022, 13:47:07) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from google.protobuf import api_pb2
>>> api_pb2.Api(source_context=api_pb2.Mixin())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Parameter to MergeFrom() must be instance of same class: expected <class 'google.protobuf.source_context_pb2.SourceContext'> got <class 'google.protobuf.api_pb2.Mixin'>.

4.23.0 will be ready in a few days