[FFmpeg-cvslog] avcodec/mpeg12dec: Fix runtime error: left shift of negative value -2

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sat Feb 25 21:07:24 2017 +0100| [aff8cf18cb0b1fa4f2e3d163c3da2f25aa6d1906] | committer: Michael Niedermayer

avcodec/mpeg12dec: Fix runtime error: left shift of negative value -2

671/clusterfuzz-testcase-4990381827555328

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=aff8cf18cb0b1fa4f2e3d163c3da2f25aa6d1906
---

 libavcodec/mpeg12dec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index 5f86029..d44ddb2 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -948,8 +948,8 @@ static int mpeg_decode_mb(MpegEncContext *s, int16_t block[12][64])
                         dmy = get_dmv(s);
 
 
-                        s->last_mv[i][0][1] = my << my_shift;
-                        s->last_mv[i][1][1] = my << my_shift;
+                        s->last_mv[i][0][1] = my * (1 << my_shift);
+                        s->last_mv[i][1][1] = my * (1 << my_shift);
 
                         s->mv[i][0][0] = mx;
                         s->mv[i][0][1] = my;