avcodec/bintext: Check font height

Fixes: division by zero
Fixes: 15257/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BINTEXT_fuzzer-5757352881422336
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/libavcodec/bintext.c b/libavcodec/bintext.c
index 49b75c9e271ea8140d3f27fea763e248aa54c8b6..1aeed21f516746e7dc1aed76d21a31f25faecf04 100644 (file)
--- a/libavcodec/bintext.c
+++ b/libavcodec/bintext.c
@@ -63,6 +63,10 @@ static av_cold int decode_init(AVCodecContext *avctx)
             av_log(avctx, AV_LOG_ERROR, "not enough extradata\n");
             return AVERROR_INVALIDDATA;
         }
+        if (!s->font_height) {
+            av_log(avctx, AV_LOG_ERROR, "invalid font height\n");
+            return AVERROR_INVALIDDATA;
+        }
     } else {
         s->font_height = 8;
         s->flags = 0;