gh-151862: Fix NULL deref on non-str AttributeError when unpickling#151863
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tonghuaroot wants to merge 2 commits into
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gh-151862: Fix NULL deref on non-str AttributeError when unpickling#151863tonghuaroot wants to merge 2 commits into
tonghuaroot wants to merge 2 commits into
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…ling An object crossing interpreters via a queue or channel is unpickled on the receive side. When that unpickling raised an ``AttributeError`` whose first argument was not a UTF-8-encodable string, ``PyUnicode_AsUTF8()`` returned ``NULL`` and the subsequent ``strncmp(NULL, ...)`` in ``check_missing___main___attr()`` dereferenced it, crashing the interpreter. Guard against the ``NULL`` result and treat it as not a missing-``__main__``-attribute error.
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Python/crossinterp.c'scheck_missing___main___attr()passed the result ofPyUnicode_AsUTF8()straight tostrncmp()without aNULLcheck.msgobjisargs[0]of anAttributeErrorraised on the receive side of the cross-interpreter pickle fallback (aconcurrent.interpretersqueue or channel). Whenargs[0]is not astr(AttributeError(42),AttributeError(b'x'),AttributeError(None)) or is astrwith lone surrogates (AttributeError('\ud800')),PyUnicode_AsUTF8()returnsNULLandstrncmp(NULL, ...)crashes the interpreter.This adds a
NULLguard matching the checked sibling helper_copy_string_obj_raw(). BecausePyUnicode_AsUTF8sets an exception on failure and the function asserts!PyErr_Occurred()on entry, the guard clears it,Py_DECREF(msgobj)(mirroring the success-path decref), and returns 0 (not a missing-__main__attribute), so the failure degrades to the normalNotShareableError.A regression test is added in
Lib/test/test_interpreters/test_queues.pycovering all fourargs[0]shapes (42,b'x',None,'\ud800'— the surrogate case is a distinct branch:args[0]is unicode but fails UTF-8 encoding), plus a positive control with normalstrargs (including the genuine missing-__main__-attribute message shape) to lock in the non-NULLstrncmp()path. Without the fix the test crashes; with it the queue raisesNotShareableError.This fixes the
check_missing___main___attr()crash reached through the queue/channel receive path. A separate crash on theInterpreter.call()result-preserve path is reported independently.