Rend2 out-of-bounds write while outside the map in the negative direction.

[Charlese2]

Reporting a bug? Please make sure you've given the following information - thanks!

Operating system and version:
Windows 11 Version 22H2 (OS build 22621.2428)

Is this for single player or multiplayer?
Multiplayer

Description of the bug (and if possible, steps to reproduce the bug):
The Remainder of a negative Dividend with a positive Divisor can be a negative number. For example this modulo -1 % 3 would result in -1. If centerZoneOffsetX (or Y) is a low enough number by noclipping outside the map while going in a negative direction, it will make the Dividend negative.

OpenJK/codemp/rd-rend2/tr_weather.cpp

Lines 1144 to 1149 in 4c422ea

	chunkIndex = (int(centerZoneOffsetX + numMinZonesX) + x + 1) % 3;
	chunkIndex += (int(centerZoneOffsetY + numMinZonesY) + y + 1) % 3 * 3;
	VectorSet2(
	zoneOffsets[chunkIndex],
	x,
	y);

If chunkIndex ends up as a negative number it writes outside of the zoneOffsets buffer.

OpenJK/codemp/rd-rend2/tr_weather.cpp

Line 1134 in 4c422ea

vec2_t zoneOffsets[9];

What did you expect to happen instead?
I expected it to not crash from stack corruption from noclipping outside the map. I know it is a obscure use case.

[paishoexpert]

I was able to replicate this on vjun1.
Will fix and open up a PR.