[FFmpeg-cvslog] avcodec/fmvc: avoid copying uninitialized data

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Feb  2 22:29:25 2021 +0100| [b24d3bfe66b5cc4eb5dbd0e2f2fdb51aa4f901a2] | committer: Michael Niedermayer

avcodec/fmvc: avoid copying uninitialized data

Fixes: Timeout
Fixes: 30049/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FMVC_fuzzer-5986909455253504

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b24d3bfe66b5cc4eb5dbd0e2f2fdb51aa4f901a2
---

 libavcodec/fmvc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavcodec/fmvc.c b/libavcodec/fmvc.c
index 5bee96a18d..3701b0849b 100644
--- a/libavcodec/fmvc.c
+++ b/libavcodec/fmvc.c
@@ -440,6 +440,8 @@ static int decode_frame(AVCodecContext *avctx, void *data,
             memcpy(dst, src, avctx->width * s->bpp);
             dst -= frame->linesize[0];
             src += s->stride * 4;
+            if (bytestream2_tell_p(pb) < y*s->stride * 4)
+                break;
         }
     } else {
         unsigned block, nb_blocks;