8000 bpo-45826: Fix a crash in suggestions.c by checking for `traceback is None` by sweeneyde · Pull Request #29590 · python/cpython · GitHub
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bpo-45826: Fix a crash in suggestions.c by checking for traceback is None #29590

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Merged
merged 5 commits into from
Nov 17, 2021
Merged

bpo-45826: Fix a crash in suggestions.c by checking for traceback is None #29590

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12cdff4
Add failing tests
sweeneyde Nov 17, 2021
430aad7
make the tests pass
sweeneyde Nov 17, 2021
daae381
📜🤖 Added by blurb_it.
blurb-it[bot] Nov 17, 2021
04a4ebb
Check for wrong type, not just for None
sweeneyde Nov 17, 2021
80c8388
Merge branch 'suggest_crash' of https://github.com/sweeneyde/cpython …
sweeneyde Nov 17, 2021
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Check for wrong type, not just for None
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@sweeneyde
sweeneyde committed Nov 17, 2021
commit 04a4ebb1f8300309680d8d723c0a5d632391716e
5 changes: 2 additions & 3 deletions Python/suggestions.c
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Expand Up @@ -203,16 +203,15 @@ offer_suggestions_for_name_error(PyNameErrorObject *exc)
// Abort if we don't have a variable name or we have an invalid one
// or if we don't have a traceback to work with
if (name == NULL || !PyUnicode_CheckExact(name) ||
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@pablogsal pablogsal Nov 17, 2021 •
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Instead of checking for None, we can check if the traceback object parent class is the traceback type (.PyTraceBack_Type) . This way we also stop segfaults if someone placed any other object there

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Isn't tb_next is supposed to be None or a Traceback? Regardless, I agree that it is more clear to just check for type.

traceback == NULL || Py_IsNone((PyObject *)traceback)
traceback == NULL || !Py_IS_TYPE(traceback, &PyTraceBack_Type)
) {
return NULL;
}

// Move to the traceback of the exception
while (1) {
assert(Py_IS_TYPE(traceback, &PyTraceBack_Type));
PyTracebackObject *next = traceback->tb_next;
if (next == NULL || Py_IsNone((PyObject *)traceback)) {
if (next == NULL || !Py_IS_TYPE(next, &PyTraceBack_Type)) {
break;
}
else {
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