mvi: Add sanity checking for the audio frame size

This avoids a division by zero.

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/mvi.c

@@ -94,6 +94,12 @@ static int read_header(AVFormatContext *s)
     mvi->get_int = (vst->codec->width * vst->codec->height < (1 << 16)) ? avio_rl16 : avio_rl24;
 
     mvi->audio_frame_size   = ((uint64_t)mvi->audio_data_size << MVI_FRAC_BITS) / frames_count;
+    if (mvi->audio_frame_size <= 1 << MVI_FRAC_BITS - 1) {
+        av_log(s, AV_LOG_ERROR, "Invalid audio_data_size (%d) or frames_count (%d)\n",
+               mvi->audio_data_size, frames_count);
+        return AVERROR_INVALIDDATA;
+    }
+
     mvi->audio_size_counter = (ast->codec->sample_rate * 830 / mvi->audio_frame_size - 1) * mvi->audio_frame_size;
     mvi->audio_size_left    = mvi->audio_data_size;