From 5253db8495df3b402d91e34ac5c7923c5e9811a4 Mon Sep 17 00:00:00 2001
From: Christian Kamm <mail@ckamm.de>
Date: Mon, 29 Jan 2024 15:01:10 +0100
Subject: [PATCH] allocator: Don't allow growth beyond heap memory region

(cherry picked from commit afc2ff9e80d443e86c09341240965c53d7f7be26)
---
 programs/mango-v4/src/allocator.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/programs/mango-v4/src/allocator.rs b/programs/mango-v4/src/allocator.rs
index 9cb72d153..9ed5e94d0 100644
--- a/programs/mango-v4/src/allocator.rs
+++ b/programs/mango-v4/src/allocator.rs
@@ -2,6 +2,11 @@
 
 use std::alloc::{GlobalAlloc, Layout};
 
+/// The end of the region where heap space may be reserved for the program.
+///
+/// The actual size of the heap is currently not available at runtime.
+pub const HEAP_END_ADDRESS: usize = 0x400000000;
+
 #[cfg(not(feature = "no-entrypoint"))]
 #[global_allocator]
 pub static ALLOCATOR: BumpAllocator = BumpAllocator {};
@@ -48,6 +53,9 @@ unsafe impl GlobalAlloc for BumpAllocator {
         let end = begin.checked_add(layout.size()).unwrap();
         *pos_ptr = end;
 
+        // Ensure huge allocations can't escape the dedicated heap memory region
+        assert!(end < HEAP_END_ADDRESS);
+
         // Write a byte to trigger heap overflow errors early
         let end_ptr = end as *mut u8;
         *end_ptr = 0;