From 7834ec5bcce6c3ae0d4ca60e26cb96e1b8993c9c Mon Sep 17 00:00:00 2001 From: Spottedleaf Date: Sat, 23 Sep 2023 22:15:09 -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(). --- ...on-on-UpgradeData.BlockFixers-class-.patch | 27 +++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 patches/server/Fix-race-condition-on-UpgradeData.BlockFixers-class-.patch diff --git a/patches/server/Fix-race-condition-on-UpgradeData.BlockFixers-class-.patch b/patches/server/Fix-race-condition-on-UpgradeData.BlockFixers-class-.patch new file mode 100644 index 000000000..050ad6d8d --- /dev/null +++ b/patches/server/Fix-race-condition-on-UpgradeData.BlockFixers-class-.patch @@ -0,0 +1,27 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Spottedleaf +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); + });