fs: : avoid out-of-bounds arguments index access

This updates fs to prevent accessing out-of-range indices on the arguments object, which is known to cause V8 optimization bailout.

Related to issues discussed here: nodejs#10323

lib/fs.js

@@ -251,7 +251,11 @@ fs.existsSync = function(path) {
 };
 
 fs.readFile = function(path, options, callback) {
-  callback = maybeCallback(arguments[arguments.length - 1]);
+  if (arguments.length) {
+    callback = maybeCallback(arguments[arguments.length - 1]);
+  } else {
+    callback = rethrow();
+  }
   options = getOptions(options, { flag: 'r' });
 
   if (!nullCheck(path, callback))
@@ -534,7 +538,13 @@ function modeNum(m, def) {
 }
 
 fs.open = function(path, flags, mode, callback_) {
-  var callback = makeCallback(arguments[arguments.length - 1]);
+  var callback;
+
+  if (arguments.length) {
+    callback = makeCallback(arguments[arguments.length - 1]);
+  } else {
+    callback = rethrow();
+  }
   mode = modeNum(mode, 0o666);
 
   if (!nullCheck(path, callback)) return;
@@ -857,7 +867,13 @@ function preprocessSymlinkDestination(path, type, linkPath) {
 
 fs.symlink = function(target, path, type_, callback_) {
   var type = (typeof type_ === 'string' ? type_ : null);
-  var callback = makeCallback(arguments[arguments.length - 1]);
+  var callback;
+
+  if (arguments.length) {
+    callback = makeCallback(arguments[arguments.length - 1]);
+  } else {
+    callback = rethrow();
+  }
 
   if (!nullCheck(target, callback)) return;
   if (!nullCheck(path, callback)) return;
@@ -1074,8 +1090,7 @@ fs.futimesSync = function(fd, atime, mtime) {
   binding.futimes(fd, atime, mtime);
 };
 
-function writeAll(fd, isUserFd, buffer, offset, length, position, callback_) {
-  var callback = maybeCallback(arguments[arguments.length - 1]);
+function writeAll(fd, isUserFd, buffer, offset, length, position, callback) {
 
   // write(fd, buffer, offset, length, position, callback)
   fs.write(fd, buffer, offset, length, position, function(writeErr, written) {
@@ -1107,7 +1122,11 @@ function writeAll(fd, isUserFd, buffer, offset, length, position, callback_) {
 }
 
 fs.writeFile = function(path, data, options, callback) {
-  callback = maybeCallback(arguments[arguments.length - 1]);
+  if (arguments.length) {
+    callback = maybeCallback(arguments[arguments.length - 1]);
+  } else {
+    callback = rethrow();
+  }
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'w' });
   const flag = options.flag || 'w';
 
@@ -1161,7 +1180,12 @@ fs.writeFileSync = function(path, data, options) {
 };
 
 fs.appendFile = function(path, data, options, callback) {
-  callback = maybeCallback(arguments[arguments.length - 1]);
+  if (arguments.length) {
+    callback = maybeCallback(arguments[arguments.length - 1]);
+  } else {
+    callback = rethrow();
+  }
+
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'a' });
 
   // Don't make changes directly on options object