Introduce CFX_UnownedPtr to detect lifetime inversion issues.

There are places where an object "child" has a raw pointer
back to object "owner" with the understanding that owner will
always outlive child.

Violating this constraint can lead to use after free, but this
requires finding two paths: one that frees the objects in the
wrong order, and one that uses the object after the free. The
purpose of this patch is to detect the constraint violation
even when the second path is not hit.

We create a template that is used in place of TYPE*. It's dtor,
when a memory tool is present, goes out and probes the first
byte of the object to which it points.  Used in "child", this
allows the memory tool to prove that the "owner" is still alive
at the time the child is destroyed, and hence the constraint is
never violated.

Change-Id: I2a6d696d51dda4a79ee2f00a6752965e058a6417
Reviewed-on: https://pdfium-review.googlesource.com/5475
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

6 files changed, 16 insertions, 13 deletions

diff --git a/core/fpdfapi/page/cpdf_contentmarkitem.cpp b/core/fpdfapi/page/cpdf_contentmarkitem.cpp
index 2c370141e2..de720b39fc 100644
--- a/core/fpdfapi/page/cpdf_contentmarkitem.cpp
+++ b/core/fpdfapi/page/cpdf_contentmarkitem.cpp
@@ -26,7 +26,7 @@ CPDF_ContentMarkItem::~CPDF_ContentMarkItem() {}
 CPDF_Dictionary* CPDF_ContentMarkItem::GetParam() const {
   switch (m_ParamType) {
     case PropertiesDict:
-      return m_pPropertiesDict;
+      return m_pPropertiesDict.Get();
     case DirectDict:
       return m_pDirectDict.get();
     case None:
diff --git a/core/fpdfapi/page/cpdf_contentmarkitem.h b/core/fpdfapi/page/cpdf_contentmarkitem.h
index ed2737111b..afd2833691 100644
--- a/core/fpdfapi/page/cpdf_contentmarkitem.h
+++ b/core/fpdfapi/page/cpdf_contentmarkitem.h
@@ -9,6 +9,7 @@
 
 #include <memory>
 
+#include "core/fxcrt/cfx_unowned_ptr.h"
 #include "core/fxcrt/fx_memory.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
@@ -37,7 +38,7 @@ class CPDF_ContentMarkItem {
  private:
   CFX_ByteString m_MarkName;
   ParamType m_ParamType;
-  CPDF_Dictionary* m_pPropertiesDict;  // not owned.
+  CFX_UnownedPtr<CPDF_Dictionary> m_pPropertiesDict;
   std::unique_ptr<CPDF_Dictionary> m_pDirectDict;
 };
 
diff --git a/core/fpdfapi/parser/cpdf_parser.cpp b/core/fpdfapi/parser/cpdf_parser.cpp
index a3e5dba40a..54b8ea0aa3 100644
--- a/core/fpdfapi/parser/cpdf_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_parser.cpp
@@ -52,8 +52,7 @@ int32_t GetStreamFirst(const CFX_RetainPtr<CPDF_StreamAcc>& pObjStream) {
 }  // namespace
 
 CPDF_Parser::CPDF_Parser()
-    : m_pDocument(nullptr),
-      m_bHasParsed(false),
+    : m_bHasParsed(false),
       m_bXRefStream(false),
       m_bVersionUpdated(false),
       m_FileVersion(0),
@@ -719,8 +718,8 @@ bool CPDF_Parser::RebuildCrossRef() {
                 last_obj = start_pos;
                 FX_FILESIZE obj_end = 0;
                 std::unique_ptr<CPDF_Object> pObject =
-                    ParseIndirectObjectAtByStrict(m_pDocument, obj_pos, objnum,
-                                                  &obj_end);
+                    ParseIndirectObjectAtByStrict(m_pDocument.Get(), obj_pos,
+                                                  objnum, &obj_end);
                 if (CPDF_Stream* pStream = ToStream(pObject.get())) {
                   if (CPDF_Dictionary* pDict = pStream->GetDict()) {
                     if ((pDict->KeyExist("Type")) &&
@@ -779,7 +778,7 @@ bool CPDF_Parser::RebuildCrossRef() {
               m_pSyntax->SetPos(pos + i - m_pSyntax->m_HeaderOffset);
 
               std::unique_ptr<CPDF_Object> pObj =
-                  m_pSyntax->GetObject(m_pDocument, 0, 0, true);
+                  m_pSyntax->GetObject(m_pDocument.Get(), 0, 0, true);
               if (pObj) {
                 if (pObj->IsDictionary() || pObj->AsStream()) {
                   CPDF_Stream* pStream = pObj->AsStream();
@@ -800,7 +799,7 @@ bool CPDF_Parser::RebuildCrossRef() {
                               pElement ? pElement->GetObjNum() : 0;
                           if (dwObjNum) {
                             m_pTrailer->SetNewFor<CPDF_Reference>(
-                                key, m_pDocument, dwObjNum);
+                                key, m_pDocument.Get(), dwObjNum);
                           } else {
                             m_pTrailer->SetFor(key, pElement->Clone());
                           }
@@ -920,7 +919,7 @@ bool CPDF_Parser::RebuildCrossRef() {
 
 bool CPDF_Parser::LoadCrossRefV5(FX_FILESIZE* pos, bool bMainXRef) {
   std::unique_ptr<CPDF_Object> pObject(
-      ParseIndirectObjectAt(m_pDocument, *pos, 0));
+      ParseIndirectObjectAt(m_pDocument.Get(), *pos, 0));
   if (!pObject)
     return false;
 
@@ -1397,7 +1396,7 @@ std::unique_ptr<CPDF_Dictionary> CPDF_Parser::LoadTrailerV4() {
   if (m_pSyntax->GetKeyword() != "trailer")
     return nullptr;
 
-  return ToDictionary(m_pSyntax->GetObject(m_pDocument, 0, 0, true));
+  return ToDictionary(m_pSyntax->GetObject(m_pDocument.Get(), 0, 0, true));
 }
 
 uint32_t CPDF_Parser::GetPermissions() const {
diff --git a/core/fpdfapi/parser/cpdf_parser.h b/core/fpdfapi/parser/cpdf_parser.h
index 7ae2d4627e..c444c99f28 100644
--- a/core/fpdfapi/parser/cpdf_parser.h
+++ b/core/fpdfapi/parser/cpdf_parser.h
@@ -12,6 +12,7 @@
 #include <set>
 #include <vector>
 
+#include "core/fxcrt/cfx_unowned_ptr.h"
 #include "core/fxcrt/fx_basic.h"
 
 class CPDF_Array;
@@ -150,7 +151,7 @@ class CPDF_Parser {
   // the objects.
   bool VerifyCrossRefV4();
 
-  CPDF_Document* m_pDocument;  // not owned
+  CFX_UnownedPtr<CPDF_Document> m_pDocument;
   bool m_bHasParsed;
   bool m_bXRefStream;
   bool m_bVersionUpdated;
diff --git a/core/fpdfapi/render/cpdf_docrenderdata.cpp b/core/fpdfapi/render/cpdf_docrenderdata.cpp
index 2d0bca4497..d03824b59e 100644
--- a/core/fpdfapi/render/cpdf_docrenderdata.cpp
+++ b/core/fpdfapi/render/cpdf_docrenderdata.cpp
@@ -88,7 +88,7 @@ CFX_RetainPtr<CPDF_TransferFunc> CPDF_DocRenderData::GetTransferFunc(
     if (!pFuncs[0])
       return nullptr;
   }
-  auto pTransfer = pdfium::MakeRetain<CPDF_TransferFunc>(m_pPDFDoc);
+  auto pTransfer = pdfium::MakeRetain<CPDF_TransferFunc>(m_pPDFDoc.Get());
   m_TransferFuncMap[pObj] = pTransfer;
 
   float input;
diff --git a/core/fpdfapi/render/cpdf_docrenderdata.h b/core/fpdfapi/render/cpdf_docrenderdata.h
index 7952f95991..949a079126 100644
--- a/core/fpdfapi/render/cpdf_docrenderdata.h
+++ b/core/fpdfapi/render/cpdf_docrenderdata.h
@@ -11,6 +11,8 @@
 
 #include "core/fpdfapi/page/cpdf_countedobject.h"
 #include "core/fpdfapi/render/cpdf_transferfunc.h"
+#include "core/fxcrt/cfx_unowned_ptr.h"
+#include "core/fxcrt/fx_system.h"
 
 class CPDF_Document;
 class CPDF_Font;
@@ -32,7 +34,7 @@ class CPDF_DocRenderData {
   void Clear(bool bRelease);
 
  private:
-  CPDF_Document* m_pPDFDoc;  // Not Owned
+  CFX_UnownedPtr<CPDF_Document> m_pPDFDoc;
   std::map<CPDF_Font*, CFX_RetainPtr<CPDF_Type3Cache>> m_Type3FaceMap;
   std::map<CPDF_Object*, CFX_RetainPtr<CPDF_TransferFunc>> m_TransferFuncMap;
 };