fs: add length validation to fs.truncate()

This commit adds validation to the length parameter of
fs.truncate(). Prior to this commit, passing a non-number would
trigger a CHECK() in the binding layer.

Backport-PR-URL: #21171
PR-URL: #20851
Fixes: #20844
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

Backport-PR-URL: #21171
Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

lib/fs.js

@@ -85,6 +85,7 @@ const {
 } = require('internal/constants');
 const {
   isUint32,
+  validateInteger,
   validateInt32,
   validateUint32
 } = require('internal/validators');
@@ -746,6 +747,7 @@ fs.truncate = function(path, len, callback) {
     len = 0;
   }
 
+  validateInteger(len, 'len');
   callback = maybeCallback(callback);
   fs.open(path, 'r+', function(er, fd) {
     if (er) return callback(er);

test/parallel/test-fs-truncate.js

@@ -179,6 +179,16 @@ function testFtruncate(cb) {
   process.on('exit', () => fs.closeSync(fd));
 
   ['', false, null, {}, []].forEach((input) => {
+    assert.throws(
+      () => fs.truncate(file5, input, common.mustNotCall()),
+      {
+        code: 'ERR_INVALID_ARG_TYPE',
+        name: 'TypeError [ERR_INVALID_ARG_TYPE]',
+        message: 'The "len" argument must be of type number. ' +
+                 `Received type ${typeof input}`
+      }
+    );
+
     assert.throws(
       () => fs.ftruncate(fd, input),
       {
@@ -191,6 +201,16 @@ function testFtruncate(cb) {
   });
 
   [-1.5, 1.5].forEach((input) => {
+    assert.throws(
+      () => fs.truncate(file5, input),
+      {
+        code: 'ERR_OUT_OF_RANGE',
+        name: 'RangeError [ERR_OUT_OF_RANGE]',
+        message: 'The value of "len" is out of range. It must be ' +
+                  `an integer. Received ${input}`
+      }
+    );
+
     assert.throws(
       () => fs.ftruncate(fd, input),
       {