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gh-142829: Fix use-after-free in Context.__eq__ via re-entrant ContextVar.set #142905

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gh-142829: Fix use-after-free in Context.__eq__ via re-entrant ContextVar.set #142905

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@Abdoulrasheed Abdoulrasheed commented Dec 17, 2025 •
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This fix holds strong references to the HAMT objects and their keys/values during comparison in _PyHamt_Eq, preventing premature deallocation.

@Abdoulrasheed Abdoulrasheed requested a review from 1st1 as a code owner December 17, 2025 20:02
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sobolevn approved these changes Dec 20, 2025
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This is what we commonly do to solve such issues.

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kumaraditya303 commented Dec 20, 2025

Can you add a test which does the same but with __hash__? I suspect that has the same issue.

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Abdoulrasheed commented Dec 20, 2025

Can you add a test which does the same but with __hash__? I suspect that has the same issue.

@kumaraditya303 I think __hash__ on values isn't called during Context comparison. only keys are hashed, and ContextVar uses a pre-computed hash. But I've added a test for it just to be safe.

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@sobolevn sobolevn sobolevn approved these changes

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