From e94a7f2996e7732284e7aaddbfcad8b264072674 Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Fri, 23 Aug 2024 15:43:05 +0200
Subject: [PATCH] buffer: truncate instead of throw when writing beyond buffer

Fixes: https://github.com/nodejs/node/issues/54523

PR-URL: https://github.com/nodejs/node/pull/54524
---
 lib/internal/buffer.js             |  9 ---------
 test.js                            | 19 +++++++++++++++++++
 test/parallel/test-buffer-write.js |  7 +++++++
 3 files changed, 26 insertions(+), 9 deletions(-)
 create mode 100644 test.js

diff --git a/lib/internal/buffer.js b/lib/internal/buffer.js
index c547c1f993fb55..f66a556c698928 100644
--- a/lib/internal/buffer.js
+++ b/lib/internal/buffer.js
@@ -1040,9 +1040,6 @@ function addBufferPrototypeMethods(proto) {
     if (offset < 0 || offset > this.byteLength) {
       throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');
     }
-    if (length < 0 || length > this.byteLength - offset) {
-      throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
-    }
     return asciiWriteStatic(this, string, offset, length);
   };
   proto.base64Write = base64Write;
@@ -1051,9 +1048,6 @@ function addBufferPrototypeMethods(proto) {
     if (offset < 0 || offset > this.byteLength) {
       throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');
     }
-    if (length < 0 || length > this.byteLength - offset) {
-      throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
-    }
     return latin1WriteStatic(this, string, offset, length);
   };
   proto.hexWrite = hexWrite;
@@ -1062,9 +1056,6 @@ function addBufferPrototypeMethods(proto) {
     if (offset < 0 || offset > this.byteLength) {
       throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');
     }
-    if (length < 0 || length > this.byteLength - offset) {
-      throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
-    }
     return utf8WriteStatic(this, string, offset, length);
   };
 }
diff --git a/test.js b/test.js
new file mode 100644
index 00000000000000..1038398edbf627
--- /dev/null
+++ b/test.js
@@ -0,0 +1,19 @@
+let i = 0;
+
+while (i < 1_000_000) {
+  const buf = Buffer.from("\x80")
+
+  if (buf[0] !== 194 || buf[1] !== 128) {
+    console.log("Unexpected return value:", buf, buf[0], buf[1]);
+    break
+  }
+
+  i++;
+}
+
+if (i < 1_000_000) {
+  console.log("FAILED after %d iterations", i);
+  process.exit(1);
+} else {
+  console.log("PASSED after %d iterations", i);
+}
diff --git a/test/parallel/test-buffer-write.js b/test/parallel/test-buffer-write.js
index 128327c47e5d6f..75913abab55046 100644
--- a/test/parallel/test-buffer-write.js
+++ b/test/parallel/test-buffer-write.js
@@ -106,3 +106,10 @@ assert.strictEqual(Buffer.alloc(4)
   assert.strictEqual(buf.write('ыы', 1, 'utf16le'), 4);
   assert.deepStrictEqual([...buf], [0, 0x4b, 0x04, 0x4b, 0x04, 0, 0, 0]);
 }
+
+
+{
+  const buf = Buffer.alloc(1);
+  assert.strictEqual(buf.write('ww'), 1);
+  assert.strictEqual(buf.toString(), 'w');
+}