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

src/core/SkValidatingReadBuffer.cpp

Index: src/core/SkValidatingReadBuffer.cpp
diff --git a/src/core/SkValidatingReadBuffer.cpp b/src/core/SkValidatingReadBuffer.cpp
index 9f094f9617f1161361452a3b8d56a6d285967a92..3084565ffdee978edb187affcb40ecdb302b3a4c 100644
--- a/src/core/SkValidatingReadBuffer.cpp
+++ b/src/core/SkValidatingReadBuffer.cpp
@@ -118,8 +118,11 @@ void SkValidatingReadBuffer::readPoint(SkPoint* point) {
 }
 
 void SkValidatingReadBuffer::readMatrix(SkMatrix* matrix) {
-    const size_t size = matrix->readFromMemory(fReader.peek());
-    this->validate(SkAlign4(size) == size);
+    size_t size = 0;
+    if (!fError) {
+        size = matrix->readFromMemory(fReader.peek(), fReader.available());
+        this->validate((SkAlign4(size) != size) || (0 == size));
+    }
     if (!fError) {
         (void)this->skip(size);
     }
@@ -140,16 +143,22 @@ void SkValidatingReadBuffer::readRect(SkRect* rect) {
 }
 
 void SkValidatingReadBuffer::readRegion(SkRegion* region) {
-    const size_t size = region->readFromMemory(fReader.peek());
-    this->validate(SkAlign4(size) == size);
+    size_t size = 0;
+    if (!fError) {
+        size = region->readFromMemory(fReader.peek(), fReader.available());
+        this->validate((SkAlign4(size) != size) || (0 == size));
+    }
     if (!fError) {
         (void)this->skip(size);
     }
 }
 
 void SkValidatingReadBuffer::readPath(SkPath* path) {
-    const size_t size = path->readFromMemory(fReader.peek());
-    this->validate(SkAlign4(size) == size);
+    size_t size = 0;
+    if (!fError) {
+        size = path->readFromMemory(fReader.peek(), fReader.available());
+        this->validate((SkAlign4(size) != size) || (0 == size));
+    }
     if (!fError) {
         (void)this->skip(size);
     }
@@ -189,6 +198,8 @@ bool SkValidatingReadBuffer::readScalarArray(SkScalar* values, size_t size) {
 }
 
 uint32_t SkValidatingReadBuffer::getArrayCount() {
+    const size_t inc = sizeof(uint32_t);
+    fError = fError || !IsPtrAlign4(fReader.peek()) || !fReader.isAvailable(inc);
     return *(uint32_t*)fReader.peek();
 }