Fix stack exhaustion in CPDF_PSProc::Parse()

core/fpdfapi/fpdf_page/cpdf_psengine.h

 // Copyright 2016 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
 
 #ifndef CORE_FPDFAPI_FPDF_PAGE_CPDF_PSENGINE_H_
 #define CORE_FPDFAPI_FPDF_PAGE_CPDF_PSENGINE_H_
 
 #include <memory>
@@ skipping 52 matching lines @@
   PSOP_CONST
 };
 
 constexpr uint32_t PSENGINE_STACKSIZE = 100;
 
 class CPDF_PSProc {
  public:
   CPDF_PSProc();
   ~CPDF_PSProc();
 
-  FX_BOOL Parse(CPDF_SimpleParser* parser);
+  FX_BOOL Parse(CPDF_SimpleParser* parser, int depth);
   FX_BOOL Execute(CPDF_PSEngine* pEngine);
 
  private:
+  static const int kMaxDepth = 128;
   std::vector<std::unique_ptr<CPDF_PSOP>> m_Operators;
 };
 
 class CPDF_PSEngine {
  public:
   CPDF_PSEngine();
   ~CPDF_PSEngine();
 
   FX_BOOL Parse(const FX_CHAR* str, int size);
   FX_BOOL Execute();
   FX_BOOL DoOperator(PDF_PSOP op);
   void Reset() { m_StackCount = 0; }
   void Push(FX_FLOAT value);
   void Push(int value) { Push((FX_FLOAT)value); }
   FX_FLOAT Pop();
   uint32_t GetStackSize() const { return m_StackCount; }
 
  private:
   FX_FLOAT m_Stack[PSENGINE_STACKSIZE];
   uint32_t m_StackCount;
   CPDF_PSProc m_MainProc;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PAGE_CPDF_PSENGINE_H_