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@niedermayer.cc>

diff --git a/libavcodec/fmvc.c b/libavcodec/fmvc.c
index 5bee96a18de4d4f4385a7161960f7dcc925d2a4c..3701b0849b79c48a26fbd34a83fe80ecb0092f66 100644 (file)
--- 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;