Correct the way to count pages and to avoid infinite loop

BUG=pdfium:360
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1585823003 .

3 files changed, 61 insertions, 46 deletions

diff --git a/core/include/fpdfapi/fpdf_parser.h b/core/include/fpdfapi/fpdf_parser.h
index fda4557119..bdddfc37d7 100644
--- a/core/include/fpdfapi/fpdf_parser.h
+++ b/core/include/fpdfapi/fpdf_parser.h
@@ -61,6 +61,20 @@ inline bool PDFCharIsLineEnding(uint8_t c) {
   return c == '\r' || c == '\n';
 }
 
+template <typename T>
+class ScopedSetInsertion {
+ public:
+  ScopedSetInsertion(std::set<T>* org_set, T elem)
+      : m_Set(org_set), m_Entry(elem) {
+    m_Set->insert(m_Entry);
+  }
+  ~ScopedSetInsertion() { m_Set->erase(m_Entry); }
+
+ private:
+  std::set<T>* const m_Set;
+  const T m_Entry;
+};
+
 // Indexed by 8-bit char code, contains unicode code points.
 extern const FX_WORD PDFDocEncoding[256];
 
@@ -168,7 +182,9 @@ class CPDF_Document : public CFX_PrivateData, public CPDF_IndirectObjectHolder {
 
   CFX_DWordArray m_PageList;
 
-  int _GetPageCount() const;
+  // Retrieve page count information by getting count value from the tree nodes
+  // or walking through the tree nodes to calculate it.
+  int RetrievePageCount() const;
   CPDF_Dictionary* _FindPDFPage(CPDF_Dictionary* pPages,
                                 int iPage,
                                 int nPagesToGo,
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
index d8091e8861..6fc3440482 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
@@ -6,7 +6,43 @@
 
 #include "core/include/fpdfapi/fpdf_parser.h"
 
+#include <set>
+
 #include "core/include/fpdfapi/fpdf_module.h"
+#include "third_party/base/stl_util.h"
+
+namespace {
+
+int CountPages(CPDF_Dictionary* pPages,
+               std::set<CPDF_Dictionary*>* visited_pages) {
+  int count = pPages->GetInteger("Count");
+  if (count > 0 && count < FPDF_PAGE_MAX_NUM) {
+    return count;
+  }
+  CPDF_Array* pKidList = pPages->GetArray("Kids");
+  if (!pKidList) {
+    return 0;
+  }
+  count = 0;
+  for (FX_DWORD i = 0; i < pKidList->GetCount(); i++) {
+    CPDF_Dictionary* pKid = pKidList->GetDict(i);
+    if (!pKid || pdfium::ContainsKey(*visited_pages, pKid)) {
+      continue;
+    }
+    if (pKid->KeyExist("Kids")) {
+      // Use |visited_pages| to help detect circular references of pages.
+      ScopedSetInsertion<CPDF_Dictionary*> local_add(visited_pages, pKid);
+      count += CountPages(pKid, visited_pages);
+    } else {
+      // This page is a leaf node.
+      count++;
+    }
+  }
+  pPages->SetAtInteger("Count", count);
+  return count;
+}
+
+}  // namespace
 
 CPDF_Document::CPDF_Document(CPDF_Parser* pParser)
     : CPDF_IndirectObjectHolder(pParser) {
@@ -54,7 +90,7 @@ void CPDF_Document::LoadDoc() {
     m_ID1 = pIDArray->GetString(0);
     m_ID2 = pIDArray->GetString(1);
   }
-  m_PageList.SetSize(_GetPageCount());
+  m_PageList.SetSize(RetrievePageCount());
 }
 void CPDF_Document::LoadAsynDoc(CPDF_Dictionary* pLinearized) {
   m_bLinearized = TRUE;
@@ -87,7 +123,7 @@ void CPDF_Document::LoadAsynDoc(CPDF_Dictionary* pLinearized) {
     m_dwFirstPageObjNum = pObjNum->GetInteger();
 }
 void CPDF_Document::LoadPages() {
-  m_PageList.SetSize(_GetPageCount());
+  m_PageList.SetSize(RetrievePageCount());
 }
 CPDF_Document::~CPDF_Document() {
   if (m_pDocPage) {
@@ -256,34 +292,8 @@ int CPDF_Document::GetPageIndex(FX_DWORD objnum) {
 int CPDF_Document::GetPageCount() const {
   return m_PageList.GetSize();
 }
-static int _CountPages(CPDF_Dictionary* pPages, int level) {
-  if (level > 128) {
-    return 0;
-  }
-  int count = pPages->GetInteger("Count");
-  if (count > 0 && count < FPDF_PAGE_MAX_NUM) {
-    return count;
-  }
-  CPDF_Array* pKidList = pPages->GetArray("Kids");
-  if (!pKidList) {
-    return 0;
-  }
-  count = 0;
-  for (FX_DWORD i = 0; i < pKidList->GetCount(); i++) {
-    CPDF_Dictionary* pKid = pKidList->GetDict(i);
-    if (!pKid) {
-      continue;
-    }
-    if (!pKid->KeyExist("Kids")) {
-      count++;
-    } else {
-      count += _CountPages(pKid, level + 1);
-    }
-  }
-  pPages->SetAtInteger("Count", count);
-  return count;
-}
-int CPDF_Document::_GetPageCount() const {
+
+int CPDF_Document::RetrievePageCount() const {
   CPDF_Dictionary* pRoot = GetRoot();
   if (!pRoot) {
     return 0;
@@ -295,8 +305,11 @@ int CPDF_Document::_GetPageCount() const {
   if (!pPages->KeyExist("Kids")) {
     return 1;
   }
-  return _CountPages(pPages, 0);
+  std::set<CPDF_Dictionary*> visited_pages;
+  visited_pages.insert(pPages);
+  return CountPages(pPages, &visited_pages);
 }
+
 FX_BOOL CPDF_Document::IsContentUsedElsewhere(FX_DWORD objnum,
                                               CPDF_Dictionary* pThisPageDict) {
   for (int i = 0; i < m_PageList.GetSize(); i++) {
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 6f0fc76fc0..03bc9aec58 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -36,20 +36,6 @@ struct SearchTagRecord {
   FX_DWORD m_Offset;
 };
 
-template <typename T>
-class ScopedSetInsertion {
- public:
-  ScopedSetInsertion(std::set<T>* org_set, T elem)
-      : m_Set(org_set), m_Entry(elem) {
-    m_Set->insert(m_Entry);
-  }
-  ~ScopedSetInsertion() { m_Set->erase(m_Entry); }
-
- private:
-  std::set<T>* const m_Set;
-  const T m_Entry;
-};
-
 int CompareFileSize(const void* p1, const void* p2) {
   return *(FX_FILESIZE*)p1 - *(FX_FILESIZE*)p2;
 }