Checking structure sizes before reading them from memory to avoid overflowing the buffer's stream.

BUG=
R=reed@google.com

Review URL: https://codereview.chromium.org/41253002

git-svn-id: http://skia.googlecode.com/svn/trunk@12114 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 17 insertions, 15 deletions

diff --git a/include/core/SkReader32.h b/include/core/SkReader32.h
index 7a8d22a80c..40ae12ce23 100644
--- a/include/core/SkReader32.h
+++ b/include/core/SkReader32.h
@@ -106,27 +106,20 @@ public:
     int32_t readS32() { return this->readInt(); }
     uint32_t readU32() { return this->readInt(); }
 
-    void readPath(SkPath* path) {
-        size_t size = path->readFromMemory(this->peek());
-        SkASSERT(SkAlign4(size) == size);
-        (void)this->skip(size);
+    bool readPath(SkPath* path) {
+        return readObjectFromMemory(path);
     }
 
-    void readMatrix(SkMatrix* matrix) {
-        size_t size = matrix->readFromMemory(this->peek());
-        SkASSERT(SkAlign4(size) == size);
-        (void)this->skip(size);
+    bool readMatrix(SkMatrix* matrix) {
+        return readObjectFromMemory(matrix);
     }
 
-    SkRRect* readRRect(SkRRect* rrect) {
-        rrect->readFromMemory(this->skip(SkRRect::kSizeInMemory));
-        return rrect;
+    bool readRRect(SkRRect* rrect) {
+        return readObjectFromMemory(rrect);
     }
 
-    void readRegion(SkRegion* rgn) {
-        size_t size = rgn->readFromMemory(this->peek());
-        SkASSERT(SkAlign4(size) == size);
-        (void)this->skip(size);
+    bool readRegion(SkRegion* rgn) {
+        return readObjectFromMemory(rgn);
     }
 
     /**
@@ -143,6 +136,15 @@ public:
     size_t readIntoString(SkString* copy);
 
 private:
+    template <typename T> bool readObjectFromMemory(T* obj) {
+        size_t size = obj->readFromMemory(this->peek(), this->available());
+        // If readFromMemory() fails (which means that available() was too small), it returns 0
+        bool success = (size > 0) && (size <= this->available()) && (SkAlign4(size) == size);
+        // In case of failure, we want to skip to the end
+        (void)this->skip(success ? size : this->available());
+        return success;
+    }
+
     // these are always 4-byte aligned
     const char* fCurr;  // current position within buffer
     const char* fStop;  // end of buffer