From: Matt Corallo <git@bluematt.me>
Date: Sun, 19 Jul 2020 21:17:03 +0000 (-0400)
Subject: Globablly limit alloc to 1.75GB
X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=2e9a6353ff6b189ed4c046c4d2765c044b9cd593;p=dnsseed-rust

Globablly limit alloc to 1.75GB
---

diff --git a/src/main.rs b/src/main.rs
index c496f14..316ca12 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -40,6 +40,48 @@ static mut TOR_PROXY: Option<SocketAddr> = None;
 pub static START_SHUTDOWN: AtomicBool = AtomicBool::new(false);
 static SCANNING: AtomicBool = AtomicBool::new(false);
 
+
+use std::alloc::{GlobalAlloc, Layout, System};
+use std::ptr;
+use std::sync::atomic::AtomicUsize;
+
+// We keep track of all memory allocated by Rust code, refusing new allocations if it exceeds
+// 1.75GB.
+//
+// Note that while Rust's std, in general, should panic in response to a null allocation, it
+// is totally conceivable that some code will instead dereference this null pointer, which
+// would violate our guarantees that Rust modules should never crash the entire application.
+//
+// In the future, as upstream Rust explores a safer allocation API (eg the Alloc API which
+// returns Results instead of raw pointers, or redefining the GlobalAlloc API to allow
+// panic!()s inside of alloc calls), we should switch to those, however these APIs are
+// currently unstable.
+const TOTAL_MEM_LIMIT_BYTES: usize = (1024 + 756) * 1024 * 1024;
+static TOTAL_MEM_ALLOCD: AtomicUsize = AtomicUsize::new(0);
+struct MemoryLimitingAllocator;
+unsafe impl GlobalAlloc for MemoryLimitingAllocator {
+	unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+		let len = layout.size();
+		if len > TOTAL_MEM_LIMIT_BYTES {
+			return ptr::null_mut();
+		}
+		if TOTAL_MEM_ALLOCD.fetch_add(len, Ordering::AcqRel) + len > TOTAL_MEM_LIMIT_BYTES {
+			TOTAL_MEM_ALLOCD.fetch_sub(len, Ordering::AcqRel);
+			return ptr::null_mut();
+		}
+		System.alloc(layout)
+	}
+
+	unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+		System.dealloc(ptr, layout);
+		TOTAL_MEM_ALLOCD.fetch_sub(layout.size(), Ordering::AcqRel);
+	}
+}
+
+#[global_allocator]
+static ALLOC: MemoryLimitingAllocator = MemoryLimitingAllocator;
+
+
 struct PeerState {
 	request: Arc<(u64, BlockHash, Block)>,
 	node_services: u64,