Check for out of bound reads in AVS decoder.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/avs.c

@@ -47,6 +47,7 @@ avs_decode_frame(AVCodecContext * avctx,
                  void *data, int *data_size, AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
+    const uint8_t *buf_end = avpkt->data + avpkt->size;
     int buf_size = avpkt->size;
     AvsContext *const avs = avctx->priv_data;
     AVFrame *picture = data;
@@ -69,6 +70,8 @@ avs_decode_frame(AVCodecContext * avctx,
     out = avs->picture.data[0];
     stride = avs->picture.linesize[0];
 
+    if (buf_end - buf < 4)
+        return AVERROR_INVALIDDATA;
     sub_type = buf[0];
     type = buf[1];
     buf += 4;
@@ -79,6 +82,8 @@ avs_decode_frame(AVCodecContext * avctx,
 
         first = AV_RL16(buf);
         last = first + AV_RL16(buf + 2);
+        if (first >= 256 || last > 256 || buf_end - buf < 4 + 4 + 3 * (last - first))
+            return AVERROR_INVALIDDATA;
         buf += 4;
         for (i=first; i<last; i++, buf+=3)
             pal[i] = (buf[0] << 18) | (buf[1] << 10) | (buf[2] << 2);
@@ -114,9 +119,13 @@ avs_decode_frame(AVCodecContext * avctx,
       return -1;
     }
 
+    if (buf_end - buf < 256 * vect_w * vect_h)
+        return AVERROR_INVALIDDATA;
     table = buf + (256 * vect_w * vect_h);
     if (sub_type != AVS_I_FRAME) {
         int map_size = ((318 / vect_w + 7) / 8) * (198 / vect_h);
+        if (buf_end - table < map_size)
+            return AVERROR_INVALIDDATA;
         init_get_bits(&change_map, table, map_size * 8);
         table += map_size;
     }
@@ -124,6 +133,8 @@ avs_decode_frame(AVCodecContext * avctx,
     for (y=0; y<198; y+=vect_h) {
         for (x=0; x<318; x+=vect_w) {
             if (sub_type == AVS_I_FRAME || get_bits1(&change_map)) {
+                if (buf_end - table < 1)
+                    return AVERROR_INVALIDDATA;
                 vect = &buf[*table++ * (vect_w * vect_h)];
                 for (j=0; j<vect_w; j++) {
                     out[(y + 0) * stride + x + j] = vect[(0 * vect_w) + j];