openresty / openresty/lua-resty-core
Don't blindly intern error strings
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- Dominant language
- Lua
- Stars
- 853
- Forks
- 286
- Avg merge
- 35m
- Merged PRs (30d)
- 1
Description
Some low level functions don't set the errmsg pointer on every possible error. Case in point, if the shdict FFI functions are called with a NULL zone, they just return NGX_ERROR, and the Lua part calls ffi_string(errmsg[0]) with an stale message, or even a NULL value. (https://github.com/openresty/lua-nginx-module/blob/master/src/ngx_http_lua_shdict.c#L2639)
This could be fixed either in Lua with more paranoid style (and acknowledge that the errmsg "might be setup or not") or on the C side making sure that the errmsg is always set before returning.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at the shdict FFI call in src/ngx_http_lua_shdict.c around line 2639, then trace the Lua code that calls ffi_string(errmsg[0]). Reproduce the NULL-zone error path and determine whether the Lua or C side should guarantee a valid error message; done means stale or NULL errmsg values are no longer interned.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- lua
- Domain
- api, backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100