[FFmpeg-cvslog] avcodec/cdtoons: Fix off by 4 check on diff_size

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Feb 20 18:51:36 2020 +0100| [d2aff350bc8250d1efe04e90822f49f4b8aea9ae] | committer: Michael Niedermayer

avcodec/cdtoons: Fix off by 4 check on diff_size

Fixes: out of array read
Fixes: 20742/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CDTOONS_fuzzer-5738148607033344

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=d2aff350bc8250d1efe04e90822f49f4b8aea9ae
---

 libavcodec/cdtoons.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/cdtoons.c b/libavcodec/cdtoons.c
index dc4fa6bf0b..d5dce6351f 100644
--- a/libavcodec/cdtoons.c
+++ b/libavcodec/cdtoons.c
@@ -269,7 +269,7 @@ static int cdtoons_decode_frame(AVCodecContext *avctx, void *data,
                 diff_size  = bytestream_get_be32(&buf);
                 width      = bytestream_get_be16(&buf);
                 height     = bytestream_get_be16(&buf);
-                if (diff_size < 4 || diff_size - 4 > eod - buf) {
+                if (diff_size < 8 || diff_size - 4 > eod - buf) {
                     av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data for Diff frame data.\n");
                     return AVERROR_INVALIDDATA;
                 }