[FFmpeg-cvslog] avcodec/shorten: Fix a negative left shift in shorten_decode_frame()

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Tue Jun  5 13:12:54 2018 +0200| [b7134d7fb679df78069648d0fb7bc54a59f9f557] | committer: Michael Niedermayer

avcodec/shorten: Fix a negative left shift in shorten_decode_frame()

Fixes: left shift of negative value -9057
Fixes: 8527/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SHORTEN_fuzzer-5666853924896768

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 a711efe922b2bf1d363bdf7f8357656c3e35021e)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b7134d7fb679df78069648d0fb7bc54a59f9f557
---

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

diff --git a/libavcodec/shorten.c b/libavcodec/shorten.c
index 0c29275df2..5f4e5ed9bc 100644
--- a/libavcodec/shorten.c
+++ b/libavcodec/shorten.c
@@ -706,7 +706,7 @@ static int shorten_decode_frame(AVCodecContext *avctx, void *data,
                 if (s->version < 2)
                     s->offset[channel][s->nmean - 1] = sum / s->blocksize;
                 else
-                    s->offset[channel][s->nmean - 1] = s->bitshift == 32 ? 0 : (sum / s->blocksize) << s->bitshift;
+                    s->offset[channel][s->nmean - 1] = s->bitshift == 32 ? 0 : (sum / s->blocksize) * (1 << s->bitshift);
             }
 
             /* copy wrap samples for use with next block */