Fix the out-of-bounds array read in the ftp response...

net/ftp/ftp_network_transaction.cc

 // Copyright (c) 2010 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 "net/ftp/ftp_network_transaction.h"
 
 #include "base/compiler_specific.h"
 #include "base/histogram.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
@@ skipping 721 matching lines @@
       std::string::size_type quote_pos = line.find('"');
       if (quote_pos != std::string::npos) {
         line = line.substr(quote_pos + 1);
         quote_pos = line.find('"');
         if (quote_pos == std::string::npos)
           return Stop(ERR_INVALID_RESPONSE);
         line = line.substr(0, quote_pos);
       }
       if (system_type_ == SYSTEM_TYPE_VMS)
         line = FtpUtil::VMSPathToUnix(line);
-      if (line[line.length() - 1] == '/')
+      if (line.length() && line[line.length() - 1] == '/')
         line.erase(line.length() - 1);
       current_remote_directory_ = line;
       next_state_ = STATE_CTRL_WRITE_TYPE;
       break;
     }
     case ERROR_CLASS_INFO_NEEDED:
       return Stop(ERR_INVALID_RESPONSE);
     case ERROR_CLASS_TRANSIENT_ERROR:
       return Stop(ERR_FAILED);
     case ERROR_CLASS_PERMANENT_ERROR:
@@ skipping 490 matching lines @@
   if (!had_error_type[type]) {
     had_error_type[type] = true;
     UMA_HISTOGRAM_ENUMERATION("Net.FtpDataConnectionErrorHappened",
         type, NUM_OF_NET_ERROR_TYPES);
   }
   UMA_HISTOGRAM_ENUMERATION("Net.FtpDataConnectionErrorCount",
       type, NUM_OF_NET_ERROR_TYPES);
 }
 
 }  // namespace net