Potential crash event with the latest GMod update

[TeddiO]

Exe build: 20:02:11 Dec 14 2021 (8438) (4000)
GMod version 2021.12.14, branch: unknown
Windows 32bit Dedicated Server

If an error is thrown before ISteamHTTP is available (e.g. close to or on server boot), the server will hang and endlessly consume RAM until the server echos not enough memory.

Example error trace:

[ERROR] HTTP failed - ISteamHTTP isn't available!
  1. Post - lua/includes/modules/http.lua:71
   2. v - gamemode/path/that/hooks
    3. unknown - lua/includes/modules/hook.lua:96
     4. HTTP - [C]:-1

[TeddiO]

Additionally after some testing with a vanilla install of GMod, even calling something via an http based function in GM:Initialize() is still too early 👀

[danielga]

To understand this issue better, is the server hang only happening with the module active? Is that example trace what seems to be causing the hang?

[danielga]

Also, can you make a small sample that reproduces the problem, so I can do it locally?

[TeddiO]

So it looks like the issue isn't to do with gm_luaerror directly, but instead there's an infinite loop when trying to handle a specific scenario.

In this particular scenario the http.Fetch (or any http* based operation) function is what's actually failing which causes gm_luaerror to attempt to handle the newly generated error, ad infinitum leading to an infinite loop.

Below is an example that should work if you dump it in to autorun/server, but at this point it's not specifically a luaerror issue anymore.

require("luaerror")
luaerror.EnableCompiletimeDetour(true)
luaerror.EnableRuntimeDetour(true)
hook.Add("LuaError", "Example", function()
    http.Fetch("https://google.com")
end)

error("This is an error")

[TeddiO]

Updated my previous comment with an updated example.

Having luaerror.EnableCompiletimeDetour set to true or luaerror.EnableRuntimeDetour set to true will help facilitate an infinite loop if used in conjunction with a http function and ISteamHTTP is not yet available.

[TeddiO]

I've included an example in gamemode format as well if that's of better / more use to you.

crash.zip

[danielga]

I've replicated the problem and it's easy to fix. However, I'm undecided on whether to completely disallow reentrancy or allow a couple loops before stopping.

[danielga]

Please try this build (when it's done).

[TeddiO]

For some reason Windows keeps flagging it as a virus when the download completes (gmsv_luaerror_win32.dll)

[danielga]

Tried it on my Windows Defender and it didn't report anything, although VirusTotal reports the same as you. https://www.virustotal.com/gui/file/dcac940d3f6c1bed2e8ca0ee5237943f56c0fec62acb48f4a407a996ae1ffd15

[danielga]

Not much I can do, I'm afraid. Detouring and signature scanning seems like relative common things for viruses.

[TeddiO]

That's fair, I'll just tell Windows to ignore it, can't help false positives!

[TeddiO]

Yep, that works! 🎉

[danielga]

Just to put it out there, I went with the no reentrancy route, which means you won't receive LuaError hook calls for errors that occurred inside a LuaError.