Fix a crashier in CPDFSDK_Document::GetPageView()

fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "fpdfsdk/include/fsdk_define.h"
 #include "fpdfsdk/include/fpdfxfa/fpdfxfa_doc.h"
 #include "fpdfsdk/include/fsdk_mgr.h"
 #include "fpdfsdk/include/fpdfxfa/fpdfxfa_app.h"
@@ skipping 27 matching lines @@
     : m_iDocType(DOCTYPE_PDF),
       m_pPDFDoc(pPDFDoc),
       m_pSDKDoc(nullptr),
       m_pXFADoc(nullptr),
       m_pXFADocView(nullptr),
       m_pApp(pProvider),
       m_pJSContext(nullptr) {
 }
 
 CPDFXFA_Document::~CPDFXFA_Document() {
-  if (m_pJSContext && m_pSDKDoc && m_pSDKDoc->GetEnv())
-    m_pSDKDoc->GetEnv()->GetJSRuntime()->ReleaseContext(m_pJSContext);
-
-  delete m_pSDKDoc;
-
-  if (m_pPDFDoc) {
-    CPDF_Parser* pParser = m_pPDFDoc->GetParser();
-    if (pParser)
-      delete pParser;
-    else
-      delete m_pPDFDoc;
-  }
   if (m_pXFADoc) {
     IXFA_App* pApp = m_pApp->GetXFAApp();
     if (pApp) {
       IXFA_DocHandler* pDocHandler = pApp->GetDocHandler();
       if (pDocHandler) {
         CloseXFADoc(pDocHandler);
       }
     }
     delete m_pXFADoc;
+    m_pXFADoc = nullptr;

[Tom Sepez, 2016/02/03 18:02:49]

These are always worrisome; if the correct operation relies on this being null,
then some other routine (as called from the dtor) is accessing the object after
the dtor has been invoked (sometimes it's the dtor itself being re-entered).
Either way, it points out a design problem. Which is why we remove these
wherever possible, so that if we see one, we know that there's a reentrancy
issue and we must tread carefully.

Do we need this assignment and the one for m_pSDKDoc below?

+  }
+  if (m_pJSContext && m_pSDKDoc && m_pSDKDoc->GetEnv())
+    m_pSDKDoc->GetEnv()->GetJSRuntime()->ReleaseContext(m_pJSContext);
+  delete m_pSDKDoc;
+  m_pSDKDoc = nullptr;
+  if (m_pPDFDoc) {
+    CPDF_Parser* pParser = m_pPDFDoc->GetParser();
+    if (pParser)
+      delete pParser;
+    else
+      delete m_pPDFDoc;
   }
 }
 
 FX_BOOL CPDFXFA_Document::LoadXFADoc() {
   if (!m_pPDFDoc)
     return FALSE;
 
   m_XFAPageList.RemoveAll();
 
   IXFA_App* pApp = m_pApp->GetXFAApp();
@@ skipping 1173 matching lines @@
   }
 
   return _GetHValueByName(szPropName, hValue,
                           m_pSDKDoc->GetEnv()->GetJSRuntime());
 }
 FX_BOOL CPDFXFA_Document::_GetHValueByName(const CFX_ByteStringC& utf8Name,
                                            FXJSE_HVALUE hValue,
                                            IJS_Runtime* runTime) {
   return runTime->GetHValueByName(utf8Name, hValue);
 }