From 41e09ec71b10a54040c10fae88e7d0892a7cc499 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Tue, 18 May 2021 23:25:15 +0200
Subject: [PATCH] child_process: retain reference to data with advanced
 serialization
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Do the same thing we do for other streams, and retain a reference to
the Buffer that was sent over IPC while the write request is active,
so that it doesn’t get garbage collected while the data is still in
flight.

(This is a good example of why it’s a bad idea that we’re not re-using
the general streams implementation for IPC and instead maintain
separate usage of the low-level I/O primitives.)

Fixes: https://github.com/nodejs/node/issues/34797

PR-URL: https://github.com/nodejs/node/pull/38728
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Minwoo Jung <nodecorelab@gmail.com>
---
 lib/internal/child_process/serialization.js   | 13 ++++++---
 ...cess-advanced-serialization-largebuffer.js | 27 +++++++++++++++++++
 2 files changed, 37 insertions(+), 3 deletions(-)
 create mode 100644 test/parallel/test-child-process-advanced-serialization-largebuffer.js

diff --git a/lib/internal/child_process/serialization.js b/lib/internal/child_process/serialization.js
index df8a6ca67236c5..30713d0315d450 100644
--- a/lib/internal/child_process/serialization.js
+++ b/lib/internal/child_process/serialization.js
@@ -10,6 +10,7 @@ const { StringDecoder } = require('string_decoder');
 const v8 = require('v8');
 const { isArrayBufferView } = require('internal/util/types');
 const assert = require('internal/assert');
+const { streamBaseState, kLastWriteWasAsync } = internalBinding('stream_wrap');
 
 const kMessageBuffer = Symbol('kMessageBuffer');
 const kJSONBuffer = Symbol('kJSONBuffer');
@@ -80,10 +81,16 @@ const advanced = {
     const serializedMessage = ser.releaseBuffer();
     const sizeBuffer = Buffer.allocUnsafe(4);
     sizeBuffer.writeUInt32BE(serializedMessage.length);
-    return channel.writeBuffer(req, Buffer.concat([
+
+    const buffer = Buffer.concat([
       sizeBuffer,
-      serializedMessage
-    ]), handle);
+      serializedMessage,
+    ]);
+    const result = channel.writeBuffer(req, buffer, handle);
+    // Mirror what stream_base_commons.js does for Buffer retention.
+    if (streamBaseState[kLastWriteWasAsync])
+      req.buffer = buffer;
+    return result;
   },
 };
 
diff --git a/test/parallel/test-child-process-advanced-serialization-largebuffer.js b/test/parallel/test-child-process-advanced-serialization-largebuffer.js
new file mode 100644
index 00000000000000..4e80bce40570f9
--- /dev/null
+++ b/test/parallel/test-child-process-advanced-serialization-largebuffer.js
@@ -0,0 +1,27 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const child_process = require('child_process');
+
+// Regression test for https://github.com/nodejs/node/issues/34797
+const eightMB = 8 * 1024 * 1024;
+
+if (process.argv[2] === 'child') {
+  for (let i = 0; i < 4; i++) {
+    process.send(new Uint8Array(eightMB).fill(i));
+  }
+} else {
+  const child = child_process.spawn(process.execPath, [__filename, 'child'], {
+    stdio: ['inherit', 'inherit', 'inherit', 'ipc'],
+    serialization: 'advanced'
+  });
+  const received = [];
+  child.on('message', common.mustCall((chunk) => {
+    assert.deepStrictEqual(chunk, new Uint8Array(eightMB).fill(chunk[0]));
+
+    received.push(chunk[0]);
+    if (received.length === 4) {
+      assert.deepStrictEqual(received, [0, 1, 2, 3]);
+    }
+  }, 4));
+}