From 7added3b39f13c89aee72491be3d082c2bc56250 Mon Sep 17 00:00:00 2001
From: Evan Lucas <evanlucas@me.com>
Date: Thu, 22 Oct 2015 06:58:26 -0500
Subject: [PATCH] fs: pass err to callback if buffer is too big

In fs.readFile, if an encoding is specified and toString fails, do not
throw an error. Instead, pass the error to the callback.

Fixes: https://github.com/nodejs/node/issues/2767
PR-URL: https://github.com/nodejs/node/pull/3485
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
---
 lib/fs.js                                     | 18 +++++--
 .../test-fs-readfile-tostring-fail.js         | 52 +++++++++++++++++++
 2 files changed, 67 insertions(+), 3 deletions(-)
 create mode 100644 test/parallel/test-fs-readfile-tostring-fail.js

diff --git a/lib/fs.js b/lib/fs.js
index 76873be14a..6345497c4f 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -395,12 +395,24 @@ function readFileAfterClose(err) {
   else
     buffer = context.buffer;
 
-  if (context.encoding)
-    buffer = buffer.toString(context.encoding);
+  if (err) return callback(err, buffer);
 
-  callback(err, buffer);
+  if (context.encoding) {
+    return tryToString(buffer, context.encoding, callback);
+  }
+
+  callback(null, buffer);
 }
 
+function tryToString(buf, encoding, callback) {
+  var e;
+  try {
+    buf = buf.toString(encoding);
+  } catch (err) {
+    e = err;
+  }
+  callback(e, buf);
+}
 
 fs.readFileSync = function(path, options) {
   if (!options) {
diff --git a/test/parallel/test-fs-readfile-tostring-fail.js b/test/parallel/test-fs-readfile-tostring-fail.js
new file mode 100644
index 0000000000..b5c4ea8f7a
--- /dev/null
+++ b/test/parallel/test-fs-readfile-tostring-fail.js
@@ -0,0 +1,52 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+const kStringMaxLength = process.binding('buffer').kStringMaxLength;
+
+common.refreshTmpDir();
+
+const file = path.join(common.tmpDir, 'toobig.txt');
+const stream = fs.createWriteStream(file, {
+  flags: 'a'
+});
+
+const size = kStringMaxLength / 200;
+const a = new Buffer(size).fill('a');
+
+for (var i = 0; i < 201; i++) {
+  stream.write(a);
+}
+
+stream.end();
+stream.on('finish', common.mustCall(function() {
+  // make sure that the toString does not throw an error
+  fs.readFile(file, 'utf8', common.mustCall(function(err, buf) {
+    assert.ok(err instanceof Error);
+    assert.strictEqual('toString failed', err.message);
+  }));
+}));
+
+function destroy() {
+  try {
+    fs.unlinkSync(file);
+  } catch (err) {
+    // it may not exist
+  }
+}
+
+process.on('exit', destroy);
+
+process.on('SIGINT', function() {
+  destroy();
+  process.exit();
+});
+
+// To make sure we don't leave a very large file
+// on test machines in the event this test fails.
+process.on('uncaughtException', function(err) {
+  destroy();
+  throw err;
+});