avcodec/vorbisdec: fix FASTDIV usage for vr_type == 2
authorMichael Niedermayer <michael@niedermayer.cc>
Fri, 6 Sep 2019 10:06:30 +0000 (12:06 +0200)
committerMichael Niedermayer <michael@niedermayer.cc>
Fri, 6 Sep 2019 20:06:12 +0000 (22:06 +0200)
This reverts a hunk from f1ca40ee00402102046fc7e59606651930436b0e

Fixes: out of array read
Fixes: 16924/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VORBIS_fuzzer-5157893162139648

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

index 104dc86..be6d1b2 100644 (file)
@@ -1513,7 +1513,7 @@ static av_always_inline int vorbis_residue_decode_internal(vorbis_context *vc,
                                 }
 
                             } else if (vr_type == 2) {
-                                unsigned voffs_div = FASTDIV(voffset << 1, ch <<1);
+                                unsigned voffs_div = ch == 1 ? voffset : FASTDIV(voffset, ch);
                                 unsigned voffs_mod = voffset - voffs_div * ch;
 
                                 for (k = 0; k < step; ++k) {