Avoid false fuzzing constraint failures at pointer boundaries - #818
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Alan-Jowett merged 1 commit intoSep 30, 2026
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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Copilot review overview
🟢 Approval recommended
The focused change correctly addresses boundary ambiguity without weakening constraints for other unknown values.
Review effort: Balanced
Findings: None
What changed in this PR
Prevents false fuzz-oracle failures by leaving ambiguous pointer-boundary values unconstrained.
Changes:
- Exempts packet, stack, and context end values from scalar constraints.
- Retains signed/unsigned constraints for other unknown values.
| File | Description |
|---|---|
libfuzzer/libfuzz_harness.cc |
Handles ambiguous boundary values during verifier constraint checks. |
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coverage: 78.594%. remained the same — Alan-Jowett:fix/fuzzer-boundary-constraints into iovisor:main |
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The fuzzing job found a minimized crash in the constraint-checking oracle for an empty packet. Values equal to data_end, stack_end, or the context boundary are ambiguous: they can represent verifier pointers or numeric values produced by arithmetic. Leave those boundary values unconstrained while retaining concrete signed/unsigned constraints for other unknown values. Reproduced and fixed the minimized crash locally; a short constrained fuzz run also completes successfully.