[FFmpeg-cvslog] avcodec/mdec: Fix runtime error: left shift of negative value -127

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Apr 27 02:27:16 2017 +0200| [6ca82975b7a8eaf676a52738ec8e7e36732327cc] | committer: Michael Niedermayer

avcodec/mdec: Fix runtime error: left shift of negative value -127

Fixes undefined behavior
Fixes: 1275/clusterfuzz-testcase-minimized-6718162017976320

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=6ca82975b7a8eaf676a52738ec8e7e36732327cc
---

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

diff --git a/libavcodec/mdec.c b/libavcodec/mdec.c
index 1cc4ca4742..42bd561cd7 100644
--- a/libavcodec/mdec.c
+++ b/libavcodec/mdec.c
@@ -73,7 +73,7 @@ static inline int mdec_decode_block_intra(MDECContext *a, int16_t *block, int n)
         if (diff >= 0xffff)
             return AVERROR_INVALIDDATA;
         a->last_dc[component] += diff;
-        block[0] = a->last_dc[component] << 3;
+        block[0] = a->last_dc[component] * (1 << 3);
     }
 
     i = 0;