[Oilpan] [NOCOMMIT] Add verifier in Member<> to detect use-after-free of on-heap objects.

third_party/WebKit/Source/platform/heap/Handle.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 638 matching lines @@
 public:
     PersistentHeapDeque() { }
 
     template<size_t otherCapacity>
     PersistentHeapDeque(const HeapDeque<T, otherCapacity>& other)
         : PersistentHeapCollectionBase<HeapDeque<T, inlineCapacity>>(other)
     {
     }
 };
 
+template<typename T, bool = IsGarbageCollectedMixin<T>::value> class GCMixinTrait;
+template<typename T>
+class GCMixinTrait<T, true> {
+public:
+    static HeapObjectHeader* heapObjectHeader(T* obj)
+    {
+        return obj->heapObjectHeader();
+    }
+};
+template<typename T>
+class GCMixinTrait<T, false> {
+public:
+    static HeapObjectHeader* heapObjectHeader(T* obj)
+    {
+        return HeapObjectHeader::fromPayload(obj);
+    }
+};
+
 // Members are used in classes to contain strong pointers to other oilpan heap
 // allocated objects.
 // All Member fields of a class must be traced in the class' trace method.
 // During the mark phase of the GC all live objects are marked as live and
 // all Member fields of a live object will be traced marked as live as well.
 template<typename T>
 class Member {
 public:
     Member() : m_raw(nullptr)
     {
+        checkPointer();
     }
 
     Member(std::nullptr_t) : m_raw(nullptr)
     {
+        checkPointer();
     }
 
     Member(T* raw) : m_raw(raw)
     {
         checkPointer();
     }
 
     explicit Member(T& raw) : m_raw(&raw)
     {
         checkPointer();
@@ skipping 72 matching lines @@
     Member& operator=(RawPtr<U> other)
     {
         m_raw = other;
         checkPointer();
         return *this;
     }
 
     Member& operator=(std::nullptr_t)
     {
         m_raw = nullptr;
+        checkPointer();
         return *this;
     }
 
     void swap(Member<T>& other)
     {
         std::swap(m_raw, other.m_raw);
         checkPointer();
     }
 
-    T* get() const { return m_raw; }
+    T* get() const
+    {
+#if ENABLE(ASSERT)
+        if (m_raw && m_gcGeneration) {
+            ASSERT(m_gcGeneration == GCMixinTrait<T>::heapObjectHeader(m_raw)->gcGeneration());
+        }
+#endif
+        return m_raw;
+    }
 
-    void clear() { m_raw = nullptr; }
+    // This method is an accessor without any security checks, and it is
+    // expected to be used under some limited condition.
+    // So do NOT use it, if you do not know what it means.
+    T* unsafeGet() const
+    {
+        return m_raw;
+    }
 
+    void clear()
+    {
+        m_raw = nullptr;
+        checkPointer();
+    }
 
 protected:
     void checkPointer()
     {
 #if ENABLE(ASSERT)
-        if (!m_raw)
+        if (!m_raw) {
+            m_gcGeneration = 0;
             return;
+        }
         // HashTable can store a special value (which is not aligned to the
         // allocation granularity) to Member<> to represent a deleted entry.
         // Thus we treat a pointer that is not aligned to the granularity
         // as a valid pointer.
         if (reinterpret_cast<intptr_t>(m_raw) % allocationGranularity)
             return;
 
         // TODO(haraken): What we really want to check here is that the pointer
         // is a traceable object. In other words, the pointer is either of:
         //
         //   (a) a pointer to the head of an on-heap object.
         //   (b) a pointer to the head of an on-heap mixin object.
         //
         // We can check it by calling Heap::isHeapObjectAlive(m_raw),
         // but we cannot call it here because it requires to include T.h.
         // So we currently only try to implement the check for (a), but do
         // not insist that T's definition is in scope.
-        if (IsFullyDefined<T>::value && !IsGarbageCollectedMixin<T>::value)
-            ASSERT(HeapObjectHeader::fromPayload(m_raw)->checkHeader());
+        if (IsFullyDefined<T>::value) {
+            m_gcGeneration = GCMixinTrait<T>::heapObjectHeader(m_raw)->gcGeneration();
+        } else {
+            m_gcGeneration = 0;
+        }
 #endif
     }
 
     T* m_raw;
 
+#if ENABLE(ASSERT)
+    uint16_t m_gcGeneration;
+#endif
+
     template<bool x, WTF::WeakHandlingFlag y, WTF::ShouldWeakPointersBeMarkedStrongly z, typename U, typename V> friend struct CollectionBackingTraceTrait;
     friend class Visitor;
-
 };
 
 // WeakMember is similar to Member in that it is used to point to other oilpan
 // heap allocated objects.
 // However instead of creating a strong pointer to the object, the WeakMember creates
 // a weak pointer, which does not keep the pointee alive. Hence if all pointers to
 // to a heap allocated object are weak the object will be garbage collected. At the
 // time of GC the weak pointers will automatically be set to null.
 template<typename T>
 class WeakMember : public Member<T> {
@@ skipping 40 matching lines @@
     WeakMember& operator=(const RawPtr<U>& other)
     {
         this->m_raw = other;
         this->checkPointer();
         return *this;
     }
 
     WeakMember& operator=(std::nullptr_t)
     {
         this->m_raw = nullptr;
+        this->checkPointer();
         return *this;
     }
 
 private:
     T** cell() const { return const_cast<T**>(&this->m_raw); }
 
     template<typename Derived> friend class VisitorHelper;
 };
 
 // UntracedMember is a pointer to an on-heap object that is not traced for some
@@ skipping 52 matching lines @@
     UntracedMember& operator=(const RawPtr<U>& other)
     {
         this->m_raw = other;
         this->checkPointer();
         return *this;
     }
 
     UntracedMember& operator=(std::nullptr_t)
     {
         this->m_raw = nullptr;
+        this->checkPointer();
         return *this;
     }
 };
 
 // Comparison operators between (Weak)Members, Persistents, and UntracedMembers.
-template<typename T, typename U> inline bool operator==(const Member<T>& a, const Member<U>& b) { return a.get() == b.get(); }
-template<typename T, typename U> inline bool operator!=(const Member<T>& a, const Member<U>& b) { return a.get() != b.get(); }
+template<typename T, typename U> inline bool operator==(const Member<T>& a, const Member<U>& b) { return a.unsafeGet() == b.unsafeGet(); }
+template<typename T, typename U> inline bool operator!=(const Member<T>& a, const Member<U>& b) { return a.unsafeGet() != b.unsafeGet(); }
 template<typename T, typename U> inline bool operator==(const Persistent<T>& a, const Persistent<U>& b) { return a.get() == b.get(); }
 template<typename T, typename U> inline bool operator!=(const Persistent<T>& a, const Persistent<U>& b) { return a.get() != b.get(); }
 
 template<typename T, typename U> inline bool operator==(const Member<T>& a, const Persistent<U>& b) { return a.get() == b.get(); }
 template<typename T, typename U> inline bool operator!=(const Member<T>& a, const Persistent<U>& b) { return a.get() != b.get(); }
 template<typename T, typename U> inline bool operator==(const Persistent<T>& a, const Member<U>& b) { return a.get() == b.get(); }
 template<typename T, typename U> inline bool operator!=(const Persistent<T>& a, const Member<U>& b) { return a.get() != b.get(); }
 
 template<typename T>
 class DummyBase {
@@ skipping 446 matching lines @@
 
 template<typename T> struct PtrHash<blink::Member<T>> : PtrHash<T*> {
     template<typename U>
     static unsigned hash(const U& key) { return PtrHash<T*>::hash(key); }
     static bool equal(T* a, const blink::Member<T>& b) { return a == b; }
     static bool equal(const blink::Member<T>& a, T* b) { return a == b; }
     template<typename U, typename V>
     static bool equal(const U& a, const V& b) { return a == b; }
 };
 
-template<typename T> struct PtrHash<blink::WeakMember<T>> : PtrHash<blink::Member<T>> {
-};
+template<typename T> struct PtrHash<blink::WeakMember<T>> : PtrHash<blink::Member<T>> { };
 
-template<typename T> struct PtrHash<blink::UntracedMember<T>> : PtrHash<blink::Member<T>> {
-};
+template<typename T> struct PtrHash<blink::UntracedMember<T>> : PtrHash<blink::Member<T>> { };
 
 // PtrHash is the default hash for hash tables with members.
 template<typename T> struct DefaultHash<blink::Member<T>> {
     using Hash = PtrHash<blink::Member<T>>;
 };
 
 template<typename T> struct DefaultHash<blink::WeakMember<T>> {
     using Hash = PtrHash<blink::WeakMember<T>>;
 };
 
@@ skipping 72 matching lines @@
     // TODO(sof): extend WTF::FunctionWrapper call overloading to also handle (CrossThread)WeakPersistent.
     static T* unwrap(const StorageType& value) { return value.get(); }
 };
 
 template<typename T>
 PassRefPtr<T> adoptRef(blink::RefCountedGarbageCollected<T>*) = delete;
 
 } // namespace WTF
 
 #endif