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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().
This commit is contained in:
Spottedleaf 2023-09-23 22:15:09 -07:00
parent 0e092b4f36
commit 7834ec5bcc
1 changed files with 27 additions and 0 deletions
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27
patches/server/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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/chunk/UpgradeData.java
+++ b/src/main/java/net/minecraft/world/level/chunk/UpgradeData.java
@@ -0,0 +0,0 @@ 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(); // Paper - force the class init so that we don't access CHUNKY_FIXERS before all BlockFixers are initialised
CHUNKY_FIXERS.forEach((logic) -> {
logic.processChunk(level);
});