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GH-97002: Prevent _PyInterpreterFrames from backing more than one PyFrameObject (GH-97996)

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Brandt Bucher 2022-10-06 16:20:01 -07:00 • committed by GitHub
parent cbf0afd8a1
commit 21a2d9ff55
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3 changed files with 91 additions and 6 deletions
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29
Python/frame.c
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@ -37,14 +37,31 @@ _PyFrame_MakeAndSetFrameObject(_PyInterpreterFrame *frame)
Py_XDECREF(error_type);
Py_XDECREF(error_value);
Py_XDECREF(error_traceback);
return NULL;
}
else {
assert(frame->owner != FRAME_OWNED_BY_FRAME_OBJECT);
assert(frame->owner != FRAME_CLEARED);
f->f_frame = frame;
frame->frame_obj = f;
PyErr_Restore(error_type, error_value, error_traceback);
PyErr_Restore(error_type, error_value, error_traceback);
if (frame->frame_obj) {
// GH-97002: How did we get into this horrible situation? Most likely,
// allocating f triggered a GC collection, which ran some code that
// *also* created the same frame... while we were in the middle of
// creating it! See test_sneaky_frame_object in test_frame.py for a
// concrete example.
//
// Regardless, just throw f away and use that frame instead, since it's
// already been exposed to user code. It's actually a bit tricky to do
// this, since we aren't backed by a real _PyInterpreterFrame anymore.
// Just pretend that we have an owned, cleared frame so frame_dealloc
// doesn't make the situation worse:
f->f_frame = (_PyInterpreterFrame *)f->_f_frame_data;
f->f_frame->owner = FRAME_CLEARED;
f->f_frame->frame_obj = f;
Py_DECREF(f);
return frame->frame_obj;
}
assert(frame->owner != FRAME_OWNED_BY_FRAME_OBJECT);
assert(frame->owner != FRAME_CLEARED);
f->f_frame = frame;
frame->frame_obj = f;
return f;
}