[FFmpeg-cvslog] avcodec/xsubdec: fix overflow in alpha handling

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Wed Oct 23 22:08:37 2019 +0200| [9ea997395909907f569787d4ba5b96352ad31a80] | committer: Michael Niedermayer

avcodec/xsubdec: fix overflow in alpha handling

Fixes: left shift of 255 by 24 places cannot be represented in type 'int'
Fixes: 18368/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_XSUB_fuzzer-5702665442426880

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=9ea997395909907f569787d4ba5b96352ad31a80
---

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

diff --git a/libavcodec/xsubdec.c b/libavcodec/xsubdec.c
index 93fd0f4d50..05c4a64ee5 100644
--- a/libavcodec/xsubdec.c
+++ b/libavcodec/xsubdec.c
@@ -130,7 +130,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
             ((uint32_t *)sub->rects[0]->data[1])[i] |= 0xff000000;
     } else {
         for (i = 0; i < sub->rects[0]->nb_colors; i++)
-            ((uint32_t *)sub->rects[0]->data[1])[i] |= *buf++ << 24;
+            ((uint32_t *)sub->rects[0]->data[1])[i] |= (unsigned)*buf++ << 24;
     }
 
 #if FF_API_AVPICTURE