[FFmpeg-cvslog] avcodec/j2kenc: Fix out of array access in encode_cblk()

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Thu Nov 30 23:42:04 2017 +0100| [79ec6381151c0db5619555cc2d75988d8f8805f6] | committer: Michael Niedermayer

avcodec/j2kenc: Fix out of array access in encode_cblk()

Fixes: 4427/clusterfuzz-testcase-minimized-5106919271301120

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 0674087004538599797688785f6ac82358abc23b)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=79ec6381151c0db5619555cc2d75988d8f8805f6
---

 libavcodec/j2kenc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/j2kenc.c b/libavcodec/j2kenc.c
index c8d3861732..baaf47422c 100644
--- a/libavcodec/j2kenc.c
+++ b/libavcodec/j2kenc.c
@@ -688,7 +688,8 @@ static void encode_cblk(Jpeg2000EncoderContext *s, Jpeg2000T1Context *t1, Jpeg20
     cblk->npasses = passno;
     cblk->ninclpasses = passno;
 
-    cblk->passes[passno-1].rate = ff_mqc_flush_to(&t1->mqc, cblk->passes[passno-1].flushed, &cblk->passes[passno-1].flushed_len);
+    if (passno)
+        cblk->passes[passno-1].rate = ff_mqc_flush_to(&t1->mqc, cblk->passes[passno-1].flushed, &cblk->passes[passno-1].flushed_len);
 }
 
 /* tier-2 routines: */