Merge commit '5569146d'

* commit '5569146d':
  adx: check that the offset is not negative

See: 30bce34bMerged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/adx.c

@@ -47,13 +47,8 @@ int avpriv_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,
         return AVERROR_INVALIDDATA;
     offset = AV_RB16(buf + 2) + 4;
 
-    if (offset < 6) {
-        av_log(avctx, AV_LOG_ERROR, "offset is prior data\n");
-        return AVERROR_INVALIDDATA;
-    }
-
     /* if copyright string is within the provided data, validate it */
-    if (bufsize >= offset && memcmp(buf + offset - 6, "(c)CRI", 6))
+    if (bufsize >= offset && offset >= 6 && memcmp(buf + offset - 6, "(c)CRI", 6))
         return AVERROR_INVALIDDATA;
 
     /* check for encoding=3 block_size=18, sample_size=4 */