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[3.11] GH-99729: Unlink frames before clearing them #100047

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Merged
pablogsal merged 4 commits into from
Dec 6, 2022
Merged

[3.11] GH-99729: Unlink frames before clearing them #100047

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3586f17
Add failing regression test
brandtbucher Nov 26, 2022
5b71873
Unlink frames before clearing them
brandtbucher Nov 26, 2022
b776d3b
blurb add
brandtbucher Nov 26, 2022
5314243
Require working threading for new test
brandtbucher Nov 26, 2022
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Unlink frames before clearing them
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@brandtbucher
brandtbucher committed Nov 26, 2022
commit 5b71873fd02f3bfff706b3466458d54df9f2b20b
18 changes: 8 additions & 10 deletions Python/ceval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1617,14 +1617,6 @@ trace_function_exit(PyThreadState *tstate, _PyInterpreterFrame *frame, PyObject
return 0;
}

static _PyInterpreterFrame *
pop_frame(PyThreadState *tstate, _PyInterpreterFrame *frame)
{
_PyInterpreterFrame *prev_frame = frame->previous;
_PyEvalFrameClearAndPop(tstate, frame);
return prev_frame;
}

/* It is only between the PRECALL instruction and the following CALL,
* that this has any meaning.
*/
Expand Down Expand Up @@ -2441,7 +2433,10 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
DTRACE_FUNCTION_EXIT();
_Py_LeaveRecursiveCallTstate(tstate);
if (!frame->is_entry) {
frame = cframe.current_frame = pop_frame(tstate, frame);
// GH-99729: We need to unlink the frame *before* clearing it:
_PyInterpreterFrame *dying = frame;
frame = cframe.current_frame = dying->previous;
_PyEvalFrameClearAndPop(tstate, dying);
_PyFrame_StackPush(frame, retval);
goto resume_frame;
}
Expand Down Expand Up @@ -5833,7 +5828,10 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
assert(tstate->cframe->current_frame == frame->previous);
return NULL;
}
frame = cframe.current_frame = pop_frame(tstate, frame);
// GH-99729: We need to unlink the frame *before* clearing it:
_PyInterpreterFrame *dying = frame;
frame = cframe.current_frame = dying->previous;
_PyEvalFrameClearAndPop(tstate, dying);

resume_with_error:
SET_LOCALS_FROM_FRAME();
Expand Down
3 changes: 3 additions & 0 deletions Python/frame.c
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Expand Up @@ -123,6 +123,9 @@ _PyFrame_Clear(_PyInterpreterFrame *frame)
* to have cleared the enclosing generator, if any. */
assert(frame->owner != FRAME_OWNED_BY_GENERATOR ||
_PyFrame_GetGenerator(frame)->gi_frame_state == FRAME_CLEARED);
// GH-99729: Clearing this frame can expose the stack (via finalizers). It's
// crucial that this frame has been unlinked, and is no longer visible:
assert(_PyThreadState_GET()->cframe->current_frame != frame);
if (frame->frame_obj) {
PyFrameObject *f = frame->frame_obj;
frame->frame_obj = NULL;
Expand Down