[FFmpeg-cvslog] avcodec/mpeg12dec: Fix invalid shift in mpeg2_fast_decode_block_intra()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Dec  5 22:35:03 2019 +0100| [c40df2166c7925fc81e1ef22563c2e32124cf1d6] | committer: Michael Niedermayer

avcodec/mpeg12dec: Fix invalid shift in mpeg2_fast_decode_block_intra()

Fixes: left shift of negative value -695
Fixes: 19232/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG1VIDEO_fuzzer-5702856963522560
Fixes: 19555/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG1VIDEO_fuzzer-5741218147598336

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c40df2166c7925fc81e1ef22563c2e32124cf1d6
---

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

diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index 17f9495a1d..3927200e74 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -586,7 +586,7 @@ static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s,
     dc = s->last_dc[component];
     dc += diff;
     s->last_dc[component] = dc;
-    block[0] = dc << (3 - s->intra_dc_precision);
+    block[0] = dc * (1 << (3 - s->intra_dc_precision));
     i = 0;
     if (s->intra_vlc_format)
         rl = &ff_rl_mpeg2;