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Fix race condition on UpgradeData.BlockFixers class init

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The CHUNKY_FIXERS field is modified during the constructors
of the BlockFixers, but the code that uses CHUNKY_FIXERS does
not properly ensure that BlockFixers has been initialised before
using it, leading to a possible race condition where instances of
BlockFixers are accessed before they have initialised correctly.

We can force the class to initialise fully before accessing the
field by calling any method on the class, and for convenience
we use values().

Fixes https://github.com/PaperMC/Folia/issues/141
This commit is contained in:
Spottedleaf 2023-08-08 17:30:30 -07:00
parent 3cf16eeaf2
commit 65667ccd07
1 changed files with 27 additions and 0 deletions
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patches/server/0025-Fix-race-condition-on-UpgradeData.BlockFixers-class-.patch Normal file
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@ -0,0 +1,27 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Tue, 8 Aug 2023 17:29:33 -0700
Subject: [PATCH] Fix race condition on UpgradeData.BlockFixers class init
The CHUNKY_FIXERS field is modified during the constructors
of the BlockFixers, but the code that uses CHUNKY_FIXERS does
not properly ensure that BlockFixers has been initialised before
using it, leading to a possible race condition where instances of
BlockFixers are accessed before they have initialised correctly.
We can force the class to initialise fully before accessing the
field by calling any method on the class, and for convenience
we use values().
diff --git a/src/main/java/net/minecraft/world/level/chunk/UpgradeData.java b/src/main/java/net/minecraft/world/level/chunk/UpgradeData.java
index 8e2a7ea230fedb9094a159a83c9d69f6df3832f3..55993be2a46f6fd8635d0562aa2b76530bd9ad3d 100644
--- a/src/main/java/net/minecraft/world/level/chunk/UpgradeData.java
+++ b/src/main/java/net/minecraft/world/level/chunk/UpgradeData.java
@@ -116,6 +116,7 @@ public class UpgradeData {
Fluid fluid = tick.type() == Fluids.EMPTY ? level.getFluidState(tick.pos()).getType() : tick.type();
level.scheduleTick(tick.pos(), fluid, tick.delay(), tick.priority());
});
+ UpgradeData.BlockFixers.values(); // Folia - force the class init so that we don't access CHUNKY_FIXERS before all BlockFixers are initialised
CHUNKY_FIXERS.forEach((logic) -> {
logic.processChunk(level);
});