fix: use-after-free in get_data_from_buffer - #677
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methane merged 3 commits intoJun 2, 2026
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KowalskiThomas
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May 26, 2026 15:48
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Pull request overview
Fixes a crash (use-after-free) when unpacking from non-contiguous buffer inputs (e.g., sliced memoryview), and adds a regression test to ensure the behavior stays correct across future changes.
Changes:
- Add a regression test that unpacks from a non-contiguous stride-2 memoryview.
- Adjust C-extension buffer handling in get_data_from_buffer to avoid premature deallocation.
- Update the pure-Python fallback Unpacker.feed() to safely handle non-contiguous memoryview inputs.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| test/test_memoryview.py | Adds a regression test covering unpacking from non-contiguous memoryview. |
| msgpack/fallback.py | Ensures fallback Unpacker.feed() can ingest non-contiguous memoryview inputs. |
| msgpack/_unpacker.pyx | Updates contiguous-copy buffer acquisition logic to prevent use-after-free. |
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- Check PyObject_GetBuffer return value and raise on failure - Avoid unnecessary tobytes() copy for contiguous memoryviews in fallback feed()
This was referenced Aug 3, 2026
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What is this PR?
There currently is a crash happening when unpacking data from a non-contiguous input.
The current PR adds a test to confirm the problem is not happening anymore as well as the fix itself.
Running the reproducer with the fix applied makes the crash go away.
This is a reproducer:
Running it results in the following: