fs: fix promises reads with pos > 4GB

cjihrig · evanlucas · commit 92d7b6c9a05a · 2018-06-12T05:07:16.000-05:00
PR-URL: nodejs/node#21148 Fixes: nodejs/node#21121 Refs: nodejs/node#21003 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com> Reviewed-By: Refael Ackermann <refack@gmail.com> Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com> Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
diff --git a/lib/internal/fs/promises.js b/lib/internal/fs/promises.js
@@ -33,7 +33,6 @@ const {
   validatePath
 } = require('internal/fs/utils');
 const {
-  isUint32,
   validateInt32,
   validateUint32
 } = require('internal/validators');
@@ -213,7 +212,7 @@ async function read(handle, buffer, offset, length, position) {
 
   validateOffsetLengthRead(offset, length, buffer.length);
 
-  if (!isUint32(position))
+  if (!Number.isSafeInteger(position))
     position = -1;
 
   const bytesRead = (await binding.read(handle.fd, buffer, offset, length,
diff --git a/test/parallel/test-fs-promises-file-handle-read.js b/test/parallel/test-fs-promises-file-handle-read.js
@@ -8,6 +8,7 @@ const common = require('../common');
 const fs = require('fs');
 const { open } = fs.promises;
 const path = require('path');
+const fixtures = require('../common/fixtures');
 const tmpdir = require('../common/tmpdir');
 const assert = require('assert');
 const tmpDir = tmpdir.path;
@@ -40,6 +41,19 @@ async function validateEmptyRead() {
   assert.deepStrictEqual(buffer.length, readAsyncHandle.bytesRead);
 }
 
+async function validateLargeRead() {
+  // Reading beyond file length (3 in this case) should return no data.
+  // This is a test for a bug where reads > uint32 would return data
+  // from the current position in the file.
+  const filePath = fixtures.path('x.txt');
+  const fileHandle = await open(filePath, 'r');
+  const pos = 0xffffffff + 1; // max-uint32 + 1
+  const readHandle = await fileHandle.read(Buffer.alloc(1), 0, 1, pos);
+
+  assert.strictEqual(readHandle.bytesRead, 0);
+}
+
 validateRead()
   .then(validateEmptyRead)
+  .then(validateLargeRead)
   .then(common.mustCall());
