fix(scripting): guard against stack overflow on deeply nested Lua reply#3547
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git-hulk merged 4 commits intoJul 9, 2026
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ReplyToRedisReply() converts a Lua return value into a RESP reply with native C++ recursion that runs after lua_pcall() returns, so Lua's own recursion guard does not apply. A deeply self-nested table could recurse until the worker thread stack overflowed and crashed the whole server (the Lua VM is shared per worker). Add a lua_checkstack() guard so such a reply fails with "reached lua stack limit" instead of crashing. Includes a Go regression test in the scripting suite. Assistant-By Claude Fable 5
git-hulk
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…l error The previous lua_checkstack() guard was not enough to fix the crash: it only fails once the Lua stack exceeds LUAI_MAXCSTACK (8000 slots), which requires ~8000 native recursion frames of ReplyToRedisReply(). Worker threads may have small stacks (512KiB by default on macOS), so the C stack still overflowed before the guard ever fired. And when the guard did fire, the error string was wrapped by thousands of nested array headers instead of being surfaced to the client as an error. Convert the Lua reply via LuaTypeToRedisReply() which tracks the nesting depth and returns StatusOr<std::string>: once the depth exceeds 100 levels, the error propagates up with the Lua stack kept balanced, and ReplyToRedisReply() discards the partial reply to return a single top-level "reached lua stack limit" error like Redis does. The regression test now covers every recursive conversion site (array element, map key, map value and set entry) and runs a correct script after each error to confirm the Lua stack is left in a good state. Assistant-By Claude Fable 5
PragmaTwice
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Jul 8, 2026
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ReplyToRedisReply() converts a Lua return value into a RESP reply with
native C++ recursion that runs after lua_pcall() returns,
so Lua's own recursion guard does not apply. A deeply self-nested table
could recurse until the worker thread stack overflowed and crashed
the whole server (the Lua VM is shared per worker).
Add a lua_checkstack() guard so such a reply fails with "reached lua stack limit"
instead of crashing. Includes a Go regression test in the scripting suite.
Assistant-By Claude Fable 5