avformat/genh: Check sample rate

Fixes: signed integer overflow: -2515507630940093440 * 4 cannot be represented in type 'long'
Fixes: 46318/clusterfuzz-testcase-minimized-ffmpeg_dem_GENH_fuzzer-5009637474172928

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

libavformat/genh.c

@@ -67,6 +67,9 @@ static int genh_read_header(AVFormatContext *s)
         return AVERROR_INVALIDDATA;
     st->codecpar->block_align = align * st->codecpar->ch_layout.nb_channels;
     st->codecpar->sample_rate = avio_rl32(s->pb);
+    if (st->codecpar->sample_rate < 0)
+        return AVERROR_INVALIDDATA;
+
     avio_skip(s->pb, 4);
     st->duration = avio_rl32(s->pb);