Shared/C++: Handle non-standard return values in MaD flow sources/sinks #19569
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…Output' and 'interpretInput' to handle non-standard return value input/output. This is needed to support C++'s ReturnValue[**] notation.
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Pull Request Overview
This PR extends the MaD flow specification to correctly handle non-standard return-value indirections (e.g. ReturnValue[*]) by delegating to a new getReturnValueKind helper in both the QL and C++ FlowSummary implementations.
Key changes:
- Introduce
getReturnValueKind(string)and updateinterpretOutput/interpretInputto use it whenReturnValuehas an argument. - Delegate
getStandardReturnValueKind()togetReturnValueKind("")in both QL and C++ modules. - Update model-as-data tests to expect indirect return-value flows (fix missing
$ irmarks).
Reviewed Changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| shared/dataflow/codeql/dataflow/internal/FlowSummaryImpl.qll | Add getReturnValueKind, extend interpretOutput/interpretInput to handle starred return kinds. |
| cpp/ql/test/library-tests/dataflow/models-as-data/tests.cpp | Update test expectations for indirect return-value sources. |
| cpp/ql/lib/semmle/code/cpp/dataflow/internal/FlowSummaryImpl.qll | Route getStandardReturnValueKind() through new getReturnValueKind. |
jketema
reviewed
May 23, 2025
Thanks! Yeah, I've started a DCA run now. I don't think we have any MaD specifications that are currently affected by this, but it doesn't hurt to double check |
|
DCA was uneventful (as expected) |
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In #19563 @jketema is adding flow sources for (among other things) GetCommandLineA which should have the following MaD specification:
["", "", False, "GetCommandLineA", "", "", "ReturnValue[*]", "local", "manual"](because it's not the pointer returned by
GetCommandLineAthat's user controlled - it's the data that's pointed to!)However, we noticed that this is not parsed correctly by the current implementation of
SourceSinkInterpretation::interpretOutputsince it only has a case forgetStandardReturnValueKind(andReturnValueis the standard return value kind, notReturnValue[*]).This PR fixes that missing case, and I've checked that this makes the MaD specifications we want to have in #19563 work 🎉