dmitry-chirkov-dremio commented on code in PR #50947:
URL: https://github.com/apache/arrow/pull/50947#discussion_r4289367590
##########
cpp/src/gandiva/gdv_string_function_stubs.cc:
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@@ -289,6 +289,14 @@ const char* gdv_fn_lower_utf8(int64_t context, const char*
data, int32_t data_le
}
// Control reaches here when we encounter a multibyte character
+ // Ensure the multibyte sequence fits within the buffer to avoid
+ // reading past data_len (truncated trailing multibyte sequence).
+ if (char_len > data_len - i) {
+ gdv_fn_set_error_for_invalid_utf8(context, data[i]);
Review Comment:
Could we also add `NativeFunction::kCanReturnErrors` to the `lower` and
`upper` registrations in `function_registry_string.cc`, following the same
NULL-handling fix as https://github.com/apache/arrow/pull/49035 for
`binary_string`? `initcap` already has the flag.
Without it, Gandiva invokes these functions even on NULL inputs, so the new
truncation checks can fail a batch on bytes belonging to a NULL slot.
Please add Projector-level regressions for both functions, following the
setup in
[`TestUtf8.TestInternalAllocs`](https://github.com/apache/arrow/blob/dd47db3afcd06f1b2737bc31250d99a2ee113ec9/cpp/src/gandiva/tests/utf8_test.cc#L360-L402).
Construct that NULL input and assert evaluation succeeds and the output
remains NULL. Direct stub tests bypass the generated validity handling and
cannot catch this.
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