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[3.11] GH-96569: Avoid undefined behavior #96616

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Merged
merged 4 commits into from
Sep 8, 2022
Merged

[3.11] GH-96569: Avoid undefined behavior #96616

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c11cf6c
Avoid undefined behavior.
markshannon Sep 6, 2022
4042eac
Add news.
markshannon Sep 5, 2022
dff7afb
Add cast and bounds check.
markshannon Sep 7, 2022
bea52cd
Update Misc/NEWS.d/next/Core and Builtins/2022-09-05-16-43-44.gh-issu…
markshannon Sep 7, 2022
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24 changes: 16 additions & 8 deletions Include/internal/pycore_frame.h
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Original file line number Diff line number Diff line change
Expand Up @@ -192,17 +192,25 @@ _PyFrame_LocalsToFast(_PyInterpreterFrame *frame, int clear);
extern _PyInterpreterFrame *
_PyThreadState_BumpFramePointerSlow(PyThreadState *tstate, size_t size);

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

static inline _PyInterpreterFrame *
_PyThreadState_BumpFramePointer(PyThreadState *tstate, size_t size)
{
PyObject **base = tstate->datastack_top;
if (base) {
PyObject **top = base + size;
assert(tstate->datastack_limit);
if (top < tstate->datastack_limit) {
tstate->datastack_top = top;
return (_PyInterpreterFrame *)base;
}
if (_PyThreadState_HasStackSpace(tstate, size)) {
_PyInterpreterFrame *res = (_PyInterpreterFrame *)tstate->datastack_top;
tstate->datastack_top += size;
return res;
}
return _PyThreadState_BumpFramePointerSlow(tstate, size);
}
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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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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Remove two cases of undefined behavior, by adding NULL checks.
16 changes: 8 additions & 8 deletions Python/pystate.c
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Expand Up @@ -2178,16 +2178,16 @@ push_chunk(PyThreadState *tstate, int size)
_PyInterpreterFrame *
_PyThreadState_BumpFramePointerSlow(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, size)) {
_PyInterpreterFrame *res = (_PyInterpreterFrame *)tstate->datastack_top;
tstate->datastack_top += size;
return res;
}
else {
tstate->datastack_top = top;
if (size > INT_MAX/2) {
PyErr_NoMemory();
return NULL;
}
return (_PyInterpreterFrame *)base;
return (_PyInterpreterFrame *)push_chunk(tstate, (int)size);
}

void
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