fs: adjust default length for fs.readSync and fsPromises/read

Makes default length reasonable when nonzero offset is set.
PR-URL: #42128
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

Author: LiviaMedeiros

doc/api/fs.md

@@ -5185,7 +5185,7 @@ changes:
 * `buffer` {Buffer|TypedArray|DataView}
 * `options` {Object}
  * `offset` {integer} **Default:** `0`
- * `length` {integer} **Default:** `buffer.byteLength`
+ * `length` {integer} **Default:** `buffer.byteLength- offset`
  * `position` {integer|bigint} **Default:** `null`
 * Returns: {number}
 

lib/fs.js

@@ -605,7 +605,7 @@ function read(fd, buffer, offset, length, position, callback) {
 
 if(arguments.length<=3){
 // Assume fs.read(fd, options, callback)
-letoptions={};
+letoptions=ObjectCreate(null);
 if(arguments.length<3){
 // This is fs.read(fd, callback)
 // buffer will be the callback
@@ -622,7 +622,7 @@ function read(fd, buffer, offset, length, position, callback) {
  buffer =Buffer.alloc(16384),
  offset =0,
  length =buffer.byteLength-offset,
- position
+ position=null
 }=options);
 }
 
@@ -687,10 +687,14 @@ function readSync(fd, buffer, offset, length, position) {
 validateBuffer(buffer);
 
 if(arguments.length<=3){
-// Assume fs.read(fd, buffer, options)
-constoptions=offset||{};
+// Assume fs.readSync(fd, buffer, options)
+constoptions=offset||ObjectCreate(null);
 
-({ offset =0, length =buffer.byteLength, position }=options);
+({
+ offset =0,
+ length =buffer.byteLength-offset,
+ position =null
+}=options);
 }
 
 if(offset==null){

lib/internal/fs/promises.js

@@ -5,6 +5,7 @@ const {
  Error,
  MathMax,
  MathMin,
+ ObjectCreate,
  NumberIsSafeInteger,
  Promise,
  PromisePrototypeThen,
@@ -510,18 +511,15 @@ async function open(path, flags, mode) {
 asyncfunctionread(handle,bufferOrOptions,offset,length,position){
 letbuffer=bufferOrOptions;
 if(!isArrayBufferView(buffer)){
-if(bufferOrOptions===undefined){
-bufferOrOptions={};
-}
-if(bufferOrOptions.buffer){
-buffer=bufferOrOptions.buffer;
-validateBuffer(buffer);
-}else{
-buffer=Buffer.alloc(16384);
-}
-offset=bufferOrOptions.offset||0;
-length=bufferOrOptions.length??buffer.byteLength;
-position=bufferOrOptions.position??null;
+bufferOrOptions??=ObjectCreate(null);
+({
+ buffer =Buffer.alloc(16384),
+ offset =0,
+ length =buffer.byteLength-offset,
+ position =null
+}=bufferOrOptions);
+
+validateBuffer(buffer);
 }
 
 if(offset==null){

test/parallel/test-fs-readSync-optional-params.js

@@ -5,23 +5,53 @@ const fixtures = require('../common/fixtures');
 constfs=require('fs');
 constassert=require('assert');
 constfilepath=fixtures.path('x.txt');
-constfd=fs.openSync(filepath,'r');
 
 constexpected=Buffer.from('xyz\n');
 
 functionrunTest(defaultBuffer,options){
-constresult=fs.readSync(fd,defaultBuffer,options);
-assert.strictEqual(result,expected.length);
-assert.deepStrictEqual(defaultBuffer,expected);
+letfd;
+try{
+fd=fs.openSync(filepath,'r');
+constresult=fs.readSync(fd,defaultBuffer,options);
+assert.strictEqual(result,expected.length);
+assert.deepStrictEqual(defaultBuffer,expected);
+}finally{
+if(fd!=null)fs.closeSync(fd);
+}
 }
 
-// Test passing in an empty options object
-runTest(Buffer.allocUnsafe(expected.length),{position: 0});
+for(constoptionsof[
 
-// Test not passing in any options object
-runTest(Buffer.allocUnsafe(expected.length));
+// Test options object
+{offset: 0},
+{length: expected.length},
+{position: 0},
+{offset: 0,length: expected.length},
+{offset: 0,position: 0},
+{length: expected.length,position: 0},
+{offset: 0,length: expected.length,position: 0},
 
-// Test passing in options
-runTest(Buffer.allocUnsafe(expected.length),{offset: 0,
-length: expected.length,
-position: 0});
+{offset: null},
+{position: null},
+{position: -1},
+{position: 0n},
+
+// Test default params
+{},
+null,
+undefined,
+
+// Test if bad params are interpreted as default (not mandatory)
+false,
+true,
+Infinity,
+42n,
+Symbol(),
+
+// Test even more malicious corner cases
+'4'.repeat(expected.length),
+newString('4444'),
+[4,4,4,4],
+]){
+runTest(Buffer.allocUnsafe(expected.length),options);
+}