feat(fuzz): add semantic property invariants to all fuzz targets + global stdout cap#159
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feat(fuzz): add semantic property invariants to all fuzz targets + global stdout cap#159
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Wrap the runner's stdout writer with a limitWriter at the start of each Run() call. Bytes beyond maxStdoutBytes (10 MiB) are silently discarded so that Write() never returns an error and script execution continues normally. This prevents unbounded memory growth from runaway loops or commands that produce excessive output. Also adds TestGlobalStdoutCapSilentlyDrops to verify the cap fires and does not truncate output below the limit. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add four invariants to every non-differential fuzz target: 1. Output bounded: assert stdout <= 10 MiB (exercises the new global cap and acts as a redundant safety net). 2. Determinism: run each script twice with identical filesystem state and assert byte-identical stdout and exit code. 3. Exit code validity: assert only 0, 1, (or 2 for commands that use it) are ever returned. 4. No panic: document that reaching the end of the fuzz body proves no panic escaped Runner.Run(). Invariant 2 is skipped for ss, ps, ip addr/link (live kernel state) and differential fuzz targets (bash comparison, not rshell vs rshell). ip route fuzz targets hold the procNetRouteMu mutex for both runs, ensuring the mocked /proc/net/route content is identical. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Splitting into two separate PRs. The global stdout cap is in #161. The fuzz invariant changes are being dropped. |
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Summary
Two safety enhancements to make RULES.md invariants machine-checked:
interp/api.go,interp/runner_expand.go): wraps the runner's stdout with alimitWriterso no script run can emit more than 10 MiB of output total, regardless of what builtins do individually. Complementary to the existing per-variable (1 MiB) and per-cmdsubst (1 MiB) caps.builtins/tests/andinterp/tests/): each fuzz target now asserts:len(stdout) <= 10 MiBss,ps,ip addr/link)api.gomeans reaching the assertion means no panic occurredTest plan
go test ./interp/... ./builtins/...passesgo test ./builtins/tests/head/ -run FuzzHeadgo test ./interp/tests/ -run TestGlobalStdoutCap🤖 Generated with Claude Code