[FFmpeg-cvslog] avcodec/shorten: Fix undefined shift in fix_bitshift()

[Michael Niedermayer]

ffmpeg | branch: release/4.0 | Michael Niedermayer <michael at niedermayer.cc> | Tue Jun  5 13:15:34 2018 +0200| [028a0c91487d8cf094239557d66edd57a114057f] | committer: Michael Niedermayer

avcodec/shorten: Fix undefined shift in fix_bitshift()

Fixes: left shift of negative value -9
Fixes: 8571/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SHORTEN_fuzzer-5715966875926528

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 606c7148231404544005c0827b83c165dd6b39a8)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=028a0c91487d8cf094239557d66edd57a114057f
---

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

diff --git a/libavcodec/shorten.c b/libavcodec/shorten.c
index f7475b4954..0bd3e1e5f7 100644
--- a/libavcodec/shorten.c
+++ b/libavcodec/shorten.c
@@ -177,7 +177,7 @@ static void fix_bitshift(ShortenContext *s, int32_t *buffer)
             buffer[i] = 0;
     } else if (s->bitshift != 0) {
         for (i = 0; i < s->blocksize; i++)
-            buffer[i] <<= s->bitshift;
+            buffer[i] *= 1 << s->bitshift;
     }
 }