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

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Merged
kumaraditya303 merged 3 commits into from
Jan 9, 2026
Merged

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

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4e7e015
gh-142829: Fix use-after-free in Context.__eq__ via re-entrant Contex…
abdoulrasheed Dec 17, 2025
c7e4a79
gh-142829: Add test for __hash__ re-entrancy in Context comparison
abdoulrasheed Dec 20, 2025
8540de5
Merge branch 'main' into fix-gh-142829-context-uaf
kumaraditya303 Jan 9, 2026
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gh-142829: Add test for __hash__ re-entrancy in Context comparison
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@abdoulrasheed
abdoulrasheed committed Dec 20, 2025
commit c7e4a790ab722f52a29e1371e0c03abc49f90268
16 changes: 16 additions & 0 deletions Lib/test/test_context.py
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Original file line number Diff line number Diff line change
Expand Up @@ -570,6 +570,22 @@ def __eq__(self, other):
ctx2.run(var.set, object())
ctx1 == ctx2

def test_context_eq_reentrant_contextvar_set_in_hash(self):
var = contextvars.ContextVar("v")
ctx1 = contextvars.Context()
ctx2 = contextvars.Context()

class ReentrantHash:
def __hash__(self):
ctx1.run(lambda: var.set(object()))
return 0
def __eq__(self, other):
return isinstance(other, ReentrantHash)

ctx1.run(var.set, ReentrantHash())
ctx2.run(var.set, ReentrantHash())
ctx1 == ctx2


# HAMT Tests

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