net: add fd protection, fix #3604

Author: pmq20

lib/net.js

@@ -26,6 +26,7 @@ const exceptionWithHostPort = util._exceptionWithHostPort;
 function noop() {}
 
 function createHandle(fd) {
+  if (TTYWrap.fdProtected(fd)) throw new Error('fd is being protected');
   var type = TTYWrap.guessHandleType(fd);
   if (type === 'PIPE') return new Pipe();
   if (type === 'TCP') return new TCP();

src/tty_wrap.cc

@@ -45,6 +45,7 @@ void TTYWrap::Initialize(Local<Object> target,
 
   env->SetMethod(target, "isTTY", IsTTY);
   env->SetMethod(target, "guessHandleType", GuessHandleType);
+  env->SetMethod(target, "fdProtected", FdProtected);
 
   target->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "TTY"), t->GetFunction());
   env->set_tty_constructor_template(t);
@@ -78,6 +79,20 @@ void TTYWrap::GuessHandleType(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(OneByteString(env->isolate(), type));
 }
 
+void TTYWrap::FdProtected(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  int32_t fd = args[0]->Int32Value();
+  CHECK_GE(fd, 0);
+
+  uv_loop_t* loop = env->event_loop();
+  bool ret = false;
+
+  if (static_cast<unsigned>(fd) < loop->nwatchers &&
+      loop->watchers[fd] != NULL)
+    ret = true;
+
+  args.GetReturnValue().Set(ret);
+}
 
 void TTYWrap::IsTTY(const FunctionCallbackInfo<Value>& args) {
   int fd = args[0]->Int32Value();

src/tty_wrap.h

@@ -24,6 +24,7 @@ class TTYWrap : public StreamWrap {
           bool readable);
 
   static void GuessHandleType(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void FdProtected(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void IsTTY(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void GetWindowSize(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetRawMode(const v8::FunctionCallbackInfo<v8::Value>& args);

test/parallel/test-net-socket-fd-protection.js

@@ -0,0 +1,25 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+
+var will_throw = function() {
+  var errors = [];
+  [ 3, 4, 5, 6, 7, 8, 9 ].forEach(function(fd) {
+    try {
+      var stream = new net.Socket({
+        fd: fd,
+        readable: false,
+        writable: true
+      });
+      stream.on('error', function() {});
+      stream.write('might crash');
+    } catch (e) {
+      errors.push(e);
+    }
+  });
+  throw errors;
+};
+
+// Should throw instead of crash
+assert.throws(will_throw, /fd is being protected/);