Try a new approach to fixing IAT unpatch crashes when the DLL is gone.

base/iat_patch.h

 // Copyright (c) 2006-2008 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.
 
 // This file declares a helpers to intercept functions from a DLL.
 //
 // This set of functions are designed to intercept functions for a
 // specific DLL imported from another DLL. This is the case when,
 // for example, we want to intercept CertDuplicateCertificateContext
 // function (exported from crypt32.dll) called by wininet.dll.
@@ skipping 62 matching lines @@
  public:
   IATPatchFunction();
   ~IATPatchFunction();
 
   // Intercept a function in an import table of a specific
   // module. Save the original function and the import
   // table address. These values will be used later
   // during Unpatch
   //
   // Arguments:
-  // module_handle          Module to be intercepted
+  // module                 Module to be intercepted
   // imported_from_module   Module that exports the 'function_name'
   // function_name          Name of the API to be intercepted
   //
   // Returns: Windows error code (winerror.h). NO_ERROR if successful
   //
-  DWORD Patch(HMODULE module_handle,
+  // Note: Patching a function will make the IAT patch take some "ownership" on
+  // |module|.  It will LoadLibrary(module) to keep the DLL alive until a call
+  // to Unpatch(), which will call FreeLibrary() and allow the module to be
+  // unloaded.  The idea is to help prevent the DLL from going away while a
+  // patch is still active.
+  //
+  DWORD Patch(const wchar_t* module,
               const char* imported_from_module,
               const char* function_name,
               void* new_function);
 
   // Unpatch the IAT entry using internally saved original
   // function.
   //
   // Returns: Windows error code (winerror.h). NO_ERROR if successful
   //
   DWORD Unpatch();
 
   bool is_patched() const {
     return (NULL != intercept_function_);
   }
 
  private:
+  HMODULE module_handle_;
   void* intercept_function_;
   void* original_function_;
   IMAGE_THUNK_DATA* iat_thunk_;
 
   DISALLOW_EVIL_CONSTRUCTORS(IATPatchFunction);
 };
 
 }  // namespace iat_patch
 
 #endif  // BASE_IAT_PATCH_H__