avformat/genh: Check block_align

Fixes: infinite loop
Fixes: 26440/clusterfuzz-testcase-minimized-ffmpeg_dem_GENH_fuzzer-5632134020333568
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavformat/genh.c b/libavformat/genh.c
index ed9910503d81d261860ba5ea8d61889180f6b7ff..698104a9d61974b1917092cb0775b4b5e48b1469 100644 (file)
--- a/libavformat/genh.c
+++ b/libavformat/genh.c
@@ -146,6 +146,9 @@ static int genh_read_header(AVFormatContext *s)
         }
     }
 
+    if (st->codecpar->block_align <= 0)
+        return AVERROR_INVALIDDATA;
+
     avio_skip(s->pb, start_offset - avio_tell(s->pb));
 
     avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);