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GH-96569: Add two NULL checks to avoid undefined behavior. #96585

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Merged
markshannon merged 4 commits into from
Sep 6, 2022
Merged

GH-96569: Add two NULL checks to avoid undefined behavior. #96585

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1f743bf
Add some NULL checks to prevent undefined behavior.
markshannon Sep 5, 2022
12d153e
Add news.
markshannon Sep 5, 2022
345f283
Use pointer difference to avoid undefined behavior.
markshannon Sep 6, 2022
0e0784b
Assert that datastack_top and datastack_limit are both NULL or neithe…
markshannon Sep 6, 2022
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4 changes: 2 additions & 2 deletions Include/internal/pycore_frame.h
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Expand Up @@ -190,11 +190,11 @@ _PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame);
void
_PyFrame_LocalsToFast(_PyInterpreterFrame *frame, int clear);


static inline bool
_PyThreadState_HasStackSpace(PyThreadState *tstate, int size)
{
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return tstate->datastack_top + size < tstate->datastack_limit;
return tstate->datastack_top != NULL &&
size < tstate->datastack_limit - tstate->datastack_top;
}

extern _PyInterpreterFrame *
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-09-05-16-43-44.gh-issue-96569.9lmTCC.rst
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@@ -0,0 +1 @@
Remove two cases of undefined behavoir, by adding NULL checks.
13 changes: 5 additions & 8 deletions Python/pystate.c
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Expand Up @@ -2195,15 +2195,12 @@ _PyInterpreterFrame *
_PyThreadState_PushFrame(PyThreadState *tstate, size_t size)
{
assert(size < INT_MAX/sizeof(PyObject *));
PyObject **base = tstate->datastack_top;
PyObject **top = base + size;
if (top >= tstate->datastack_limit) {
base = push_chunk(tstate, (int)size);
if (_PyThreadState_HasStackSpace(tstate, (int)size)) {
_PyInterpreterFrame *res = (_PyInterpreterFrame *)tstate->datastack_top;
tstate->datastack_top += size;
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return res;
}
else {
tstate->datastack_top = top;
}
return (_PyInterpreterFrame *)base;
return (_PyInterpreterFrame *)push_chunk(tstate, (int)size);
}

void
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