avformat/ads: Check size

Fixes: signed integer overflow: -2147483616 - 64 cannot be represented in type 'int'
Fixes: 26910/clusterfuzz-testcase-minimized-ffmpeg_dem_ADS_fuzzer-6617769344892928

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit c78b2b138c)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/ads.c

@@ -34,8 +34,9 @@ static int ads_probe(const AVProbeData *p)
 
 static int ads_read_header(AVFormatContext *s)
 {
-    int align, codec, size;
+    int align, codec;
     AVStream *st;
+    int64_t size;
 
     st = avformat_new_stream(s, NULL);
     if (!st)
@@ -62,7 +63,7 @@ static int ads_read_header(AVFormatContext *s)
     st->codecpar->block_align = st->codecpar->channels * align;
     avio_skip(s->pb, 12);
     size = avio_rl32(s->pb);
-    if (st->codecpar->codec_id == AV_CODEC_ID_ADPCM_PSX)
+    if (st->codecpar->codec_id == AV_CODEC_ID_ADPCM_PSX && size >= 0x40)
         st->duration = (size - 0x40) / 16 / st->codecpar->channels * 28;
     avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);