Changeset 179702 in webkit

Timestamp:

Feb 5, 2015, 1:29:19 PM (12 years ago)

Author:

Chris Dumez

Message:

Free memory read under MemoryCache::pruneLiveResourcesToSize()
​https://bugs.webkit.org/show_bug.cgi?id=141292
<rdar://problem/19725522>

Reviewed by Antti Koivisto.

In MemoryCache::pruneLiveResourcesToSize(), we were iterating over the
m_liveDecodedResources ListHashSet and possibly calling
CachedResource::destroyDecodedData() on the current value. Doing so
would cause a call to ListHashSet::remove() to remove the value pointed
by the current iterator, thus invalidating our iterator.

In this patch, we increment the ListHashSet iterator *before* calling
CachedResource::destroyDecodedData(), while the current iterator is
still valid. Note that this is safe because unlike iteration of most
WTF Hash data structures, iteration is guaranteed safe against mutation
of the ListHashSet, except for removal of the item currently pointed to
by a given iterator.

Test: http/tests/cache/memory-cache-pruning.html

• loader/cache/MemoryCache.cpp:

(WebCore::MemoryCache::pruneLiveResourcesToSize):

Location:

trunk

Files:

• LayoutTests/http/tests/cache/memory-cache-pruning-expected.txt (added)
• LayoutTests/http/tests/cache/memory-cache-pruning.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/WebCore.exp.in (modified) (1 diff)
• Source/WebCore/loader/cache/MemoryCache.cpp (modified) (2 diffs)
• Source/WebCore/loader/cache/MemoryCache.h (modified) (2 diffs)
• Source/WebCore/testing/Internals.cpp (modified) (1 diff)
• Source/WebCore/testing/Internals.h (modified) (1 diff)
• Source/WebCore/testing/Internals.idl (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2015-02-05  Chris Dumez  <cdumez@apple.com>
+
+        Free memory read under MemoryCache::pruneLiveResourcesToSize()
+        https://bugs.webkit.org/show_bug.cgi?id=141292
+        <rdar://problem/19725522>
+
+        Reviewed by Antti Koivisto.
+
+        In MemoryCache::pruneLiveResourcesToSize(), we were iterating over the
+        m_liveDecodedResources ListHashSet and possibly calling
+        CachedResource::destroyDecodedData() on the current value. Doing so
+        would cause a call to ListHashSet::remove() to remove the value pointed
+        by the current iterator, thus invalidating our iterator.
+
+        In this patch, we increment the ListHashSet iterator *before* calling
+        CachedResource::destroyDecodedData(), while the current iterator is
+        still valid. Note that this is safe because unlike iteration of most
+        WTF Hash data structures, iteration is guaranteed safe against mutation
+        of the ListHashSet, except for removal of the item currently pointed to
+        by a given iterator.
+
+        Test: http/tests/cache/memory-cache-pruning.html
+
+        * loader/cache/MemoryCache.cpp:
+        (WebCore::MemoryCache::pruneLiveResourcesToSize):
+
 2015-02-05  Jer Noble  <jer.noble@apple.com>
 

trunk/Source/WebCore/WebCore.exp.in

@@ -198 +198 @@
 __ZN7WebCore11MemoryCache19getOriginsWithCacheERN3WTF7HashSetINS1_6RefPtrINS_14SecurityOriginEEENS_18SecurityOriginHashENS1_10HashTraitsIS5_EEEE
 __ZN7WebCore11MemoryCache20removeImageFromCacheERKNS_3URLERKN3WTF6StringE
+__ZN7WebCore11MemoryCache24pruneDeadResourcesToSizeEj
+__ZN7WebCore11MemoryCache24pruneLiveResourcesToSizeEjb
 __ZN7WebCore11MemoryCache25removeResourcesWithOriginERNS_14SecurityOriginE
 __ZN7WebCore11MemoryCache9singletonEv

trunk/Source/WebCore/loader/cache/MemoryCache.cpp

@@ -301 +301 @@
     // greater than the current->m_lastDecodedAccessTime.
     // For more details see: https://bugs.webkit.org/show_bug.cgi?id=30209
-    for (auto* current : m_liveDecodedResources) {
+    auto it = m_liveDecodedResources.begin();
+    while (it != m_liveDecodedResources.end()) {
+        auto* current = *it;
+
+        // Increment the iterator now because the call to destroyDecodedData() below
+        // may cause a call to ListHashSet::remove() and invalidate the current
+        // iterator. Note that this is safe because unlike iteration of most
+        // WTF Hash data structures, iteration is guaranteed safe against mutation
+        // of the ListHashSet, except for removal of the item currently pointed to
+        // by a given iterator.
+        ++it;
+
         ASSERT(current->hasClients());
         if (current->isLoaded() && current->decodedSize()) {
@@ -312 +323 @@
                 continue;
 
-            // Destroy our decoded data. This will remove us from 
-            // m_liveDecodedResources, and possibly move us to a different LRU 
-            // list in m_allResources.
+            // Destroy our decoded data. This will remove us from m_liveDecodedResources, and possibly move us
+            // to a different LRU list in m_allResources.
             current->destroyDecodedData();
 

trunk/Source/WebCore/loader/cache/MemoryCache.h

@@ -63 +63 @@
     WTF_MAKE_NONCOPYABLE(MemoryCache); WTF_MAKE_FAST_ALLOCATED;
     friend NeverDestroyed<MemoryCache>;
-
+    friend class Internals;
 public:
     struct TypeStatistic {
@@ -118 +118 @@
     
     void prune();
+    unsigned size() const { return m_liveSize + m_deadSize; }
 
     void setDeadDecodedDataDeletionInterval(std::chrono::milliseconds interval) { m_deadDecodedDataDeletionInterval = interval; }

trunk/Source/WebCore/testing/Internals.cpp

@@ -410 +410 @@
 }
 
+void Internals::pruneMemoryCacheToSize(unsigned size)
+{
+    MemoryCache::singleton().pruneDeadResourcesToSize(size);
+    MemoryCache::singleton().pruneLiveResourcesToSize(size, true);
+}
+
+unsigned Internals::memoryCacheSize() const
+{
+    return MemoryCache::singleton().size();
+}
+
 Node* Internals::treeScopeRootNode(Node* node, ExceptionCode& ec)
 {

trunk/Source/WebCore/testing/Internals.h

@@ -85 +85 @@
     bool isLoadingFromMemoryCache(const String& url);
     String xhrResponseSource(XMLHttpRequest*);
+
     void clearMemoryCache();
+    void pruneMemoryCacheToSize(unsigned size);
+    unsigned memoryCacheSize() const;
 
     PassRefPtr<CSSComputedStyleDeclaration> computedStyleIncludingVisitedInfo(Node*, ExceptionCode&) const;

trunk/Source/WebCore/testing/Internals.idl

@@ -45 +45 @@
     DOMString xhrResponseSource(XMLHttpRequest xhr);
     void clearMemoryCache();
+    void pruneMemoryCacheToSize(long size);
+    long memoryCacheSize();
 
     [RaisesException] CSSStyleDeclaration computedStyleIncludingVisitedInfo(Node node);