[FFmpeg-cvslog] avcodec/dvdsubdec: Fix off by 1 error

[Michael Niedermayer]

ffmpeg | branch: release/3.1 | Michael Niedermayer <michael at niedermayer.cc> | Wed Oct 26 00:11:52 2016 +0200| [37ff66d1bde72f7fa89cd5c606d7288fb445852e] | committer: Michael Niedermayer

avcodec/dvdsubdec: Fix off by 1 error

Fixes out of array read

Found-by: Thomas Garnier using libFuzzer
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit c92f55847a3d9cd12db60bfcd0831ff7f089c37c)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=37ff66d1bde72f7fa89cd5c606d7288fb445852e
---

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

diff --git a/libavcodec/dvdsubdec.c b/libavcodec/dvdsubdec.c
index 783a24f..4ae63b4 100644
--- a/libavcodec/dvdsubdec.c
+++ b/libavcodec/dvdsubdec.c
@@ -185,7 +185,7 @@ static void guess_palette(DVDSubContext* ctx,
     for(i = 0; i < 4; i++) {
         if (alpha[i] != 0) {
             if (!color_used[colormap[i]])  {
-                level = level_map[nb_opaque_colors][j];
+                level = level_map[nb_opaque_colors - 1][j];
                 r = (((subtitle_color >> 16) & 0xff) * level) >> 8;
                 g = (((subtitle_color >> 8) & 0xff) * level) >> 8;
                 b = (((subtitle_color >> 0) & 0xff) * level) >> 8;