Properly validate data size

With "show_existing_frame" frames:
Minimum data size for profile 0 and 1 is 1 byte (8bits)
Minimum data size for profile 2 and 3 is 2 bytes (9bits)

Otherwise:
Minimum data size is 8 bytes.

This resolves the VP9 failure in fuzzing test build #56.

Change-Id: I146d9d37688f535dd68d24aacc76d464ccffdf04

vp9/vp9_dx_iface.c

diff --git a/vp9/vp9_dx_iface.c b/vp9/vp9_dx_iface.c
index 43bf35f..b917787 100644
--- a/vp9/vp9_dx_iface.c
+++ b/vp9/vp9_dx_iface.c
@@ -148,7 +148,11 @@
     if (frame_marker != VP9_FRAME_MARKER)
       return VPX_CODEC_UNSUP_BITSTREAM;
 
-    if (profile >= MAX_PROFILES) return VPX_CODEC_UNSUP_BITSTREAM;
+    if (profile >= MAX_PROFILES)
+      return VPX_CODEC_UNSUP_BITSTREAM;
+
+    if ((profile >= 2 && data_sz <= 1) || data_sz < 1)
+      return VPX_CODEC_UNSUP_BITSTREAM;
 
     if (vp9_rb_read_bit(&rb)) {  // show an existing frame
       vp9_rb_read_literal(&rb, 3);  // Frame buffer to show.