avcodec/vc1_pred: Fix invalid shift in scaleforsame()
authorMichael Niedermayer <michael@niedermayer.cc>
Wed, 10 Jul 2019 21:27:19 +0000 (23:27 +0200)
committerMichael Niedermayer <michael@niedermayer.cc>
Wed, 31 Jul 2019 18:35:07 +0000 (20:35 +0200)
Fixes: left shift of negative value -1
Fixes: 15531/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1IMAGE_fuzzer-5759556258365440

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
libavcodec/vc1_pred.c

index 9e29b44..1656506 100644 (file)
@@ -178,7 +178,7 @@ static av_always_inline int scaleforsame(VC1Context *v, int i, int n /* MV */,
     brfd      = FFMIN(v->brfd, 3);
     scalesame = ff_vc1_b_field_mvpred_scales[0][brfd];
 
-    n = (n * scalesame >> 8) << hpel;
+    n = (n * scalesame >> 8) * (1 << hpel);
     return n;
 }