avformat/rmdec: Check for overflow in ff_rm_read_mdpr_codecdata()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 03abf55f)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/rmdec.c

@@ -412,7 +412,11 @@ ff_rm_read_mdpr_codecdata (AVFormatContext *s, AVIOContext *pb,
 skip:
     /* skip codec info */
     size = avio_tell(pb) - codec_pos;
-    avio_skip(pb, codec_data_size - size);
+    if (codec_data_size >= size) {
+        avio_skip(pb, codec_data_size - size);
+    } else {
+        av_log(s, AV_LOG_WARNING, "codec_data_size %u < size %d\n", codec_data_size, size);
+    }
 
     return 0;
 }