Convert non-error panics to errors in protect - #144
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protect() asserted that every recovered value is an error, but the VM
panics with plain strings in many places (panic("unreachable"),
panic("XMove not implemented yet"), the "expected opcode" invariants in
the bytecode interpreter). Any of those turned into a second panic -
"interface conversion: string is not error" - crashing the host and
losing the original message.
Pass real errors through unchanged and wrap anything else with
fmt.Errorf, so a protected call always returns an error.
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Running Lua code can panic the host Go program.
protect()recovers a panic and asserts the value is anerror:But the VM panics with plain strings all over —
panic("unreachable"),panic("XMove not implemented yet"),"expected opcode %s, got %s"in the interpreter. Those hit the type assertion and panic again, so the panic escapesProtectedCalland takes down the process:The bytecode invariants (
expected opcode,opExtraArg) are reachable fromload()of an untrusted binary chunk.Fix: pass errors through unchanged, wrap anything else with
fmt.Errorf, so a protected call always returns an error instead of panicking.TestPanicWithStringdrivesdebug.gethook()(apanic("string")site) throughProtectedCall— it panics without the fix, returns an error with it.