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@niedermayer.cc>

diff --git a/libavcodec/shorten.c b/libavcodec/shorten.c
index f7475b49549c68864db3ebf6382d5773ace07489..0bd3e1e5f73eda9af659549b40256037f7c15063 100644 (file)
--- 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;
     }
 }