[CrOS Tether] Fix a buffer overflow issue caught by the ASAN bots.

chromeos/components/tether/ble_scanner.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromeos/components/tether/ble_scanner.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_util.h"
 #include "chromeos/components/tether/ble_constants.h"
@@ skipping 210 matching lines @@
   if (!service_data || service_data->size() < kMinNumBytesInServiceData) {
     // If there is no service data or the service data is of insufficient
     // length, there is not enough information to create a connection.
     return;
   }
 
   // Convert the service data from a std::vector<uint8_t> to a std::string.
   std::string service_data_str;
   char* string_contents_ptr =
       base::WriteInto(&service_data_str, service_data->size() + 1);
-  memcpy(string_contents_ptr, service_data->data(), service_data->size() + 1);
+  memcpy(string_contents_ptr, service_data->data(), service_data->size());
 
   CheckForMatchingScanFilters(bluetooth_device, service_data_str);
 }
 
 void BleScanner::CheckForMatchingScanFilters(
     device::BluetoothDevice* bluetooth_device,
     std::string& service_data) {
   std::vector<cryptauth::BeaconSeed> beacon_seeds;
   if (!local_device_data_provider_->GetLocalDeviceData(nullptr,
                                                        &beacon_seeds)) {
@@ skipping 12 matching lines @@
 
   for (auto& observer : observer_list_) {
     observer.OnReceivedAdvertisementFromDevice(bluetooth_device->GetAddress(),
                                                *identified_device);
   }
 }
 
 }  // namespace tether
 
 }  // namespace chromeos