Prevent malformed ICO files from recursively decoding

src/images/SkImageDecoder_libico.cpp

Index: src/images/SkImageDecoder_libico.cpp
diff --git a/src/images/SkImageDecoder_libico.cpp b/src/images/SkImageDecoder_libico.cpp
index f75d80439f5c3cc2b07baed38fff90d79acfda4f..7855546a2ccb5d849e4405c184a6d9a671d99b55 100644
--- a/src/images/SkImageDecoder_libico.cpp
+++ b/src/images/SkImageDecoder_libico.cpp
@@ -164,6 +164,10 @@ bool SkICOImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode)
         SkMemoryStream subStream(buf + offset, size, false);
         SkAutoTDelete<SkImageDecoder> otherDecoder(SkImageDecoder::Factory(&subStream));
         if (otherDecoder.get() != NULL) {
+            // Disallow nesting ICO files within one another

[reed1, 2014/08/26 17:53:34]

Can we add a test case/data for this?

+            if (otherDecoder->getFormat() == SkImageDecoder::kICO_Format) {

[scroggo, 2014/10/14 22:58:23]

We could be more aggressive here; I think the only supported sub type is PNG.

+                return false;
+            }
             // Set fields on the other decoder to be the same as this one.
             this->copyFieldsToOther(otherDecoder.get());
             if(otherDecoder->decode(&subStream, bm, this->getDefaultPref(), mode)) {