[FFmpeg-cvslog] avcodec/mpeg12dec: Fix runtime error: left shift of negative value -1

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Mar 12 03:04:04 2017 +0100| [a720b854b0d3f0fae2b1eac644dd39e5821cacb1] | committer: Michael Niedermayer

avcodec/mpeg12dec: Fix runtime error: left shift of negative value -1

Fixes: 764/clusterfuzz-testcase-6273034652483584

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a720b854b0d3f0fae2b1eac644dd39e5821cacb1
---

 libavcodec/mpeg12dec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index 27db14c..e49167f 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -994,7 +994,7 @@ static int mpeg_decode_mb(MpegEncContext *s, int16_t block[12][64])
 
             cbp = get_vlc2(&s->gb, ff_mb_pat_vlc.table, MB_PAT_VLC_BITS, 1);
             if (mb_block_count > 6) {
-                cbp <<= mb_block_count - 6;
+                cbp *= 1 << mb_block_count - 6;
                 cbp  |= get_bits(&s->gb, mb_block_count - 6);
                 s->bdsp.clear_blocks(s->block[6]);
             }