Fix out of bounds access

Bug: 34618607
Change-Id: I84f0ef948414d0b2d54e8948b6c30b8ae4da2b36
(cherry picked from commit d1c19c57f66d91ea8033c8fa6510a8760a6e663b)

media/libstagefright/id3/ID3.cpp

diff --git a/media/libstagefright/id3/ID3.cpp b/media/libstagefright/id3/ID3.cpp
index 33f79fd..8b80ae9 100644
--- a/media/libstagefright/id3/ID3.cpp
+++ b/media/libstagefright/id3/ID3.cpp
@@ -379,7 +379,7 @@
             flags &= ~1;
         }
 
-        if (flags & 2) {
+        if ((flags & 2) && (dataSize >= 2)) {
             // This file has "unsynchronization", so we have to replace occurrences
             // of 0xff 0x00 with just 0xff in order to get the real data.
 
@@ -395,11 +395,15 @@
                 mData[writeOffset++] = mData[readOffset++];
             }
             // move the remaining data following this frame
-            memmove(&mData[writeOffset], &mData[readOffset], oldSize - readOffset);
+            if (readOffset <= oldSize) {
+                memmove(&mData[writeOffset], &mData[readOffset], oldSize - readOffset);
+            } else {
+                ALOGE("b/34618607 (%zu %zu %zu %zu)", readOffset, writeOffset, oldSize, mSize);
+                android_errorWriteLog(0x534e4554, "34618607");
+            }
 
-            flags &= ~2;
         }
-
+        flags &= ~2;
         if (flags != prevFlags || iTunesHack) {
             WriteSyncsafeInteger(&mData[offset + 4], dataSize);
             mData[offset + 8] = flags >> 8;