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GH-159101: Fix UAF when tp_finalize changes the base class - #159888
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sergey-miryanov merged 7 commits intoNov 7, 2026
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October 20, 2026 15:24
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Oct 20, 2026
…e-159101.vFwrZY.rst Co-authored-by: Peter Bierma <[email protected]>
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@nascheme @pablogsal Could you please take a look? |
pablogsal
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Nov 5, 2026
sergey-miryanov
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needs backport to 3.14
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Thanks @sergey-miryanov for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15. |
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GH-161534 is a backport of this pull request to the 3.15 branch. |
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GH-161535 is a backport of this pull request to the 3.14 branch. |
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There are two issues to address.
First, we fix the UAF in
PyObject_CallFinalizer. We set theFINALIZEDflag before callingtp_finalize, so we don't need to call_PyType_IS_GCagain. Bothgc.candgc_free_threading.cdo the same.Second, after calling
PyObject_CallFinalizerFromDealloc, we extract the type ofselfagain to get the updated type, and the rest works correctly. We do the same fortp_dellater in the code.