fs: validate encoding to binding.writeString()

lib/fs.js

@@ -133,6 +133,7 @@ const {
   validateBoolean,
   validateBuffer,
   validateCallback,
+  validateEncoding,
   validateFunction,
   validateInteger,
 } = require('internal/validators');
@@ -702,11 +703,14 @@ function write(fd, buffer, offset, length, position, callback) {
     }
     length = 'utf8';
   }
+
+  const str = String(buffer);
+  validateEncoding(str, length);
   callback = maybeCallback(position);
 
   const req = new FSReqCallback();
   req.oncomplete = wrapper;
-  return binding.writeString(fd, String(buffer), offset, length, req);
+  return binding.writeString(fd, str, offset, length, req);
 }
 
 ObjectDefineProperty(write, internalUtil.customPromisifyArgs,
@@ -735,6 +739,7 @@ function writeSync(fd, buffer, offset, length, position) {
                                  undefined, ctx);
   } else {
     validateStringAfterArrayBufferView(buffer, 'buffer');
+    validateEncoding(buffer, length);
 
     if (offset === undefined)
       offset = null;

lib/internal/fs/promises.js

@@ -70,6 +70,7 @@ const {
   validateAbortSignal,
   validateBoolean,
   validateBuffer,
+  validateEncoding,
   validateInteger,
 } = require('internal/validators');
 const pathModule = require('path');
@@ -467,6 +468,7 @@ async function write(handle, buffer, offset, length, position) {
   }
 
   validateStringAfterArrayBufferView(buffer, 'buffer');
+  validateEncoding(buffer, length);
   const bytesWritten = (await binding.writeString(handle.fd, buffer, offset,
                                                   length, kUsePromises)) || 0;
   return { bytesWritten, buffer };

test/parallel/test-fs-promises.js

@@ -436,6 +436,22 @@ async function getHandle(dest) {
       );
     }
 
+    // Regression test for https://github.com/nodejs/node/issues/38168
+    {
+      const handle = await getHandle(dest);
+
+      assert.rejects(
+        async () => handle.write('abc', 0, 'hex'),
+        {
+          code: 'ERR_INVALID_ARG_VALUE',
+          message: /'encoding' is invalid for data of length 3/
+        }
+      );
+
+      const ret = await handle.write('abcd', 0, 'hex');
+      assert.strictEqual(ret.bytesWritten, 2);
+      await handle.close();
+    }
   }
 
   doTest().then(common.mustCall());

test/parallel/test-fs-write.js

@@ -33,6 +33,7 @@ const fn = path.join(tmpdir.path, 'write.txt');
 const fn2 = path.join(tmpdir.path, 'write2.txt');
 const fn3 = path.join(tmpdir.path, 'write3.txt');
 const fn4 = path.join(tmpdir.path, 'write4.txt');
+const fn5 = path.join(tmpdir.path, 'write5.txt');
 const expected = 'ümlaut.';
 const constants = fs.constants;
 
@@ -170,3 +171,31 @@ fs.open(fn4, 'w', 0o644, common.mustSucceed((fd) => {
     }
   );
 });
+
+{
+  // Regression test for https://github.com/nodejs/node/issues/38168
+  const fd = fs.openSync(fn5, 'w');
+
+  assert.throws(
+    () => fs.writeSync(fd, 'abc', 0, 'hex'),
+    {
+      code: 'ERR_INVALID_ARG_VALUE',
+      message: /'encoding' is invalid for data of length 3/
+    }
+  );
+
+  assert.throws(
+    () => fs.writeSync(fd, 'abc', 0, 'hex', common.mustNotCall()),
+    {
+      code: 'ERR_INVALID_ARG_VALUE',
+      message: /'encoding' is invalid for data of length 3/
+    }
+  );
+
+  assert.strictEqual(fs.writeSync(fd, 'abcd', 0, 'hex'), 2);
+
+  fs.write(fd, 'abcd', 0, 'hex', common.mustSucceed((written) => {
+    assert.strictEqual(written, 2);
+    fs.closeSync(fd);
+  }));
+}