avcodec/rv10: Check input for minimal frame size

Fixes: Timeout (18sec -> 4sec)
Fixes: 18012/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RV20_fuzzer-5767486145822720

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/rv10.c

@@ -550,7 +550,7 @@ static av_cold int rv10_decode_end(AVCodecContext *avctx)
 }
 
 static int rv10_decode_packet(AVCodecContext *avctx, const uint8_t *buf,
-                              int buf_size, int buf_size2)
+                              int buf_size, int buf_size2, int whole_size)
 {
     RVDecContext *rv = avctx->priv_data;
     MpegEncContext *s = &rv->m;
@@ -580,6 +580,9 @@ static int rv10_decode_packet(AVCodecContext *avctx, const uint8_t *buf,
         return AVERROR_INVALIDDATA;
     }
 
+    if (whole_size < s->mb_width * s->mb_height / 8)
+        return AVERROR_INVALIDDATA;
+
     if ((s->mb_x == 0 && s->mb_y == 0) || !s->current_picture_ptr) {
         // FIXME write parser so we always have complete frames?
         if (s->current_picture_ptr) {
@@ -754,7 +757,7 @@ static int rv10_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
             offset + FFMAX(size, size2) > buf_size)
             return AVERROR_INVALIDDATA;
 
-        if ((ret = rv10_decode_packet(avctx, buf + offset, size, size2)) < 0)
+        if ((ret = rv10_decode_packet(avctx, buf + offset, size, size2, buf_size)) < 0)
             return ret;
 
         if (ret > 8 * size)