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gh-158196: Fix double free of FileIO stat_atopen #159153

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gh-158196: Fix double free of FileIO stat_atopen #159153

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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-10-11-02-50-00.gh-issue-158196.Km2pLw.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a crash (double free) in the :term:`free-threaded build` when ``close()``
or ``truncate()`` is called concurrently on the same unbuffered
:class:`io.FileIO` object.
8 changes: 2 additions & 6 deletions Modules/_io/fileio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -142,8 +142,7 @@ internal_close(fileio *self)
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS
}
PyMem_Free(self->stat_atopen);
self->stat_atopen = NULL;
PyMem_Free(_Py_atomic_exchange_ptr(&self->stat_atopen, NULL));
if (err < 0) {
errno = save_errno;
PyErr_SetFromErrno(PyExc_OSError);
Expand Down Expand Up @@ -1148,10 +1147,7 @@ _io_FileIO_truncate_impl(fileio *self, PyTypeObject *cls, PyObject *posobj)
/* Since the file was truncated, its size at open is no longer accurate
as an estimate. Clear out the stat result, and rely on dynamic resize
code if a readall is requested. */
if (self->stat_atopen != NULL) {
PyMem_Free(self->stat_atopen);
self->stat_atopen = NULL;
}
PyMem_Free(_Py_atomic_exchange_ptr(&self->stat_atopen, NULL));

return posobj;
}
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