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, 12 insertions, 9 deletions

diff --git a/fpdfsdk/pdfwindow/PWL_ComboBox.cpp b/fpdfsdk/pdfwindow/PWL_ComboBox.cpp
index 9321e0f606..9f5ab97858 100644
--- a/fpdfsdk/pdfwindow/PWL_ComboBox.cpp
+++ b/fpdfsdk/pdfwindow/PWL_ComboBox.cpp
@@ -265,7 +265,7 @@ void CPWL_ComboBox::CreateEdit(const PWL_CREATEPARAM& cp) {
     return;
 
   m_pEdit = pdfium::MakeUnique<CPWL_CBEdit>();
-  m_pEdit->AttachFFLData(m_pFormFiller);
+  m_pEdit->AttachFFLData(m_pFormFiller.Get());
 
   PWL_CREATEPARAM ecp = cp;
   ecp.pParentWnd = this;
@@ -306,7 +306,7 @@ void CPWL_ComboBox::CreateListBox(const PWL_CREATEPARAM& cp) {
     return;
 
   m_pList = pdfium::MakeUnique<CPWL_CBListBox>();
-  m_pList->AttachFFLData(m_pFormFiller);
+  m_pList->AttachFFLData(m_pFormFiller.Get());
 
   PWL_CREATEPARAM lcp = cp;
   lcp.pParentWnd = this;
diff --git a/fpdfsdk/pdfwindow/PWL_ComboBox.h b/fpdfsdk/pdfwindow/PWL_ComboBox.h
index a687eb8e94..19d9ab2a04 100644
--- a/fpdfsdk/pdfwindow/PWL_ComboBox.h
+++ b/fpdfsdk/pdfwindow/PWL_ComboBox.h
@@ -9,6 +9,7 @@
 
 #include <memory>
 
+#include "core/fxcrt/cfx_unowned_ptr.h"
 #include "fpdfsdk/pdfwindow/PWL_Edit.h"
 #include "fpdfsdk/pdfwindow/PWL_ListBox.h"
 #include "fpdfsdk/pdfwindow/PWL_Wnd.h"
@@ -100,7 +101,7 @@ class CPWL_ComboBox : public CPWL_Wnd {
   int32_t m_nPopupWhere;
   int32_t m_nSelectItem;
   IPWL_Filler_Notify* m_pFillerNotify;
-  CFFL_FormFiller* m_pFormFiller;  // Not owned.
+  CFX_UnownedPtr<CFFL_FormFiller> m_pFormFiller;
 };
 
 #endif  // FPDFSDK_PDFWINDOW_PWL_COMBOBOX_H_
diff --git a/fpdfsdk/pdfwindow/PWL_Edit.cpp b/fpdfsdk/pdfwindow/PWL_Edit.cpp
index 90572746da..4e37e9bde4 100644
--- a/fpdfsdk/pdfwindow/PWL_Edit.cpp
+++ b/fpdfsdk/pdfwindow/PWL_Edit.cpp
@@ -398,7 +398,7 @@ void CPWL_Edit::DrawThisAppearance(CFX_RenderDevice* pDevice,
   CFX_SystemHandler* pSysHandler = GetSystemHandler();
   CFX_Edit::DrawEdit(pDevice, pUser2Device, m_pEdit.get(),
                      GetTextColor().ToFXColor(GetTransparency()), rcClip,
-                     CFX_PointF(), pRange, pSysHandler, m_pFormFiller);
+                     CFX_PointF(), pRange, pSysHandler, m_pFormFiller.Get());
 }
 
 bool CPWL_Edit::OnLButtonDown(const CFX_PointF& point, uint32_t nFlag) {
diff --git a/fpdfsdk/pdfwindow/PWL_Edit.h b/fpdfsdk/pdfwindow/PWL_Edit.h
index 5e1a36610d..bd3799141a 100644
--- a/fpdfsdk/pdfwindow/PWL_Edit.h
+++ b/fpdfsdk/pdfwindow/PWL_Edit.h
@@ -9,6 +9,7 @@
 
 #include <vector>
 
+#include "core/fxcrt/cfx_unowned_ptr.h"
 #include "core/fxcrt/fx_basic.h"
 #include "fpdfsdk/fxedit/fx_edit.h"
 #include "fpdfsdk/pdfwindow/PWL_EditCtrl.h"
@@ -136,7 +137,7 @@ class CPWL_Edit : public CPWL_EditCtrl {
   IPWL_Filler_Notify* m_pFillerNotify;
   bool m_bFocus;
   CFX_FloatRect m_rcOldWindow;
-  CFFL_FormFiller* m_pFormFiller;  // Not owned.
+  CFX_UnownedPtr<CFFL_FormFiller> m_pFormFiller;
 };
 
 #endif  // FPDFSDK_PDFWINDOW_PWL_EDIT_H_
diff --git a/fpdfsdk/pdfwindow/PWL_ListBox.cpp b/fpdfsdk/pdfwindow/PWL_ListBox.cpp
index 8448204a74..b682959426 100644
--- a/fpdfsdk/pdfwindow/PWL_ListBox.cpp
+++ b/fpdfsdk/pdfwindow/PWL_ListBox.cpp
@@ -172,14 +172,14 @@ void CPWL_ListBox::DrawThisAppearance(CFX_RenderDevice* pDevice,
       if (pSysHandler && pSysHandler->IsSelectionImplemented()) {
         CFX_Edit::DrawEdit(pDevice, pUser2Device, m_pList->GetItemEdit(i),
                            GetTextColor().ToFXColor(255), rcList, ptOffset,
-                           nullptr, pSysHandler, m_pFormFiller);
-        pSysHandler->OutputSelectedRect(m_pFormFiller, rcItem);
+                           nullptr, pSysHandler, m_pFormFiller.Get());
+        pSysHandler->OutputSelectedRect(m_pFormFiller.Get(), rcItem);
       } else {
         CPWL_Utils::DrawFillRect(pDevice, pUser2Device, rcItem,
                                  ArgbEncode(255, 0, 51, 113));
         CFX_Edit::DrawEdit(pDevice, pUser2Device, m_pList->GetItemEdit(i),
                            ArgbEncode(255, 255, 255, 255), rcList, ptOffset,
-                           nullptr, pSysHandler, m_pFormFiller);
+                           nullptr, pSysHandler, m_pFormFiller.Get());
       }
     } else {
       CFX_SystemHandler* pSysHandler = GetSystemHandler();
diff --git a/fpdfsdk/pdfwindow/PWL_ListBox.h b/fpdfsdk/pdfwindow/PWL_ListBox.h
index 9f8f464efb..0de9c91195 100644
--- a/fpdfsdk/pdfwindow/PWL_ListBox.h
+++ b/fpdfsdk/pdfwindow/PWL_ListBox.h
@@ -9,6 +9,7 @@
 
 #include <memory>
 
+#include "core/fxcrt/cfx_unowned_ptr.h"
 #include "fpdfsdk/fxedit/fx_edit.h"
 #include "fpdfsdk/pdfwindow/PWL_Wnd.h"
 
@@ -111,7 +112,7 @@ class CPWL_ListBox : public CPWL_Wnd {
   IPWL_Filler_Notify* m_pFillerNotify;
 
  private:
-  CFFL_FormFiller* m_pFormFiller;  // Not owned.
+  CFX_UnownedPtr<CFFL_FormFiller> m_pFormFiller;
 };
 
 #endif  // FPDFSDK_PDFWINDOW_PWL_LISTBOX_H_