avcodec/idcinvideo: Check side data size before use

Fixes out of array read
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/idcinvideo.c

@@ -214,7 +214,8 @@ static int idcin_decode_frame(AVCodecContext *avctx,
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     IdcinContext *s = avctx->priv_data;
-    const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, NULL);
+    int pal_size;
+    const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, &pal_size);
     AVFrame *frame = data;
     int ret;
 
@@ -227,9 +228,11 @@ static int idcin_decode_frame(AVCodecContext *avctx,
     if (idcin_decode_vlcs(s, frame))
         return AVERROR_INVALIDDATA;
 
-    if (pal) {
+    if (pal && pal_size == AVPALETTE_SIZE) {
         frame->palette_has_changed = 1;
         memcpy(s->pal, pal, AVPALETTE_SIZE);
+    } else if (pal) {
+        av_log(avctx, AV_LOG_ERROR, "Palette size %d is wrong\n", pal_size);
     }
     /* make the palette available on the way out */
     memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);