[FFmpeg-cvslog] avcodec/vc1dec: Check field_mode for sprites

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Sun Dec  8 20:18:07 2019 +0100| [e0952984786657bd0f514f5b2ce037b20c0cf554] | committer: Michael Niedermayer

avcodec/vc1dec: Check field_mode for sprites

Fixes: Out of array read
Fixes: 19263/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1IMAGE_fuzzer-5389219325542400

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 32fb9198360402941e49aa878b9d33737b654f62)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=e0952984786657bd0f514f5b2ce037b20c0cf554
---

 libavcodec/vc1dec.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 77fafbb2c3..e7cffc2978 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -865,7 +865,12 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
         ret = AVERROR_INVALIDDATA;
         goto err;
     }
-
+    if ((avctx->codec_id == AV_CODEC_ID_WMV3IMAGE || avctx->codec_id == AV_CODEC_ID_VC1IMAGE)
+        && v->field_mode) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "Sprite decoder: expected Frames not Fields\n");
+        ret = AVERROR_INVALIDDATA;
+        goto err;
+    }
     if ((s->mb_height >> v->field_mode) == 0) {
         av_log(v->s.avctx, AV_LOG_ERROR, "image too short\n");
         ret = AVERROR_INVALIDDATA;