eatgv: check vector_bits

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>

libavcodec/eatgv.c

@@ -154,6 +154,12 @@ static int tgv_decode_inter(TgvContext * s, const uint8_t *buf, const uint8_t *b
     vector_bits       = AV_RL16(&buf[6]);
     buf += 12;
 
+    if (vector_bits > MIN_CACHE_BITS || !vector_bits) {
+        av_log(s->avctx, AV_LOG_ERROR,
+               "Invalid value for motion vector bits: %d\n", vector_bits);
+        return AVERROR_INVALIDDATA;
+    }
+
     /* allocate codebook buffers as necessary */
     if (num_mvs > s->num_mvs) {
         s->mv_codebook = av_realloc(s->mv_codebook, num_mvs*2*sizeof(int));