[FFmpeg-cvslog] avcodec/vorbisdec: Check parameters in vorbis_floor0_decode() before divide

[Michael Niedermayer]

ffmpeg | branch: release/4.2 | Michael Niedermayer <michael at niedermayer.cc> | Sun Aug  4 12:28:55 2019 +0200| [4c16a8fe671968ffb9b07f402e451e44b1cac161] | committer: Michael Niedermayer

avcodec/vorbisdec: Check parameters in vorbis_floor0_decode() before divide

Fixes: division by zero
Fixes: 16183/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VORBIS_fuzzer-5688966782648320

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit aecc9b96d613f54d772e9475738bb54e0e1f182e)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=4c16a8fe671968ffb9b07f402e451e44b1cac161
---

 libavcodec/vorbisdec.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c
index a86d4c4c36..793f079737 100644
--- a/libavcodec/vorbisdec.c
+++ b/libavcodec/vorbisdec.c
@@ -1182,6 +1182,9 @@ static int vorbis_floor0_decode(vorbis_context *vc,
                     q *= q;
                 }
 
+                if (p + q == 0.0)
+                    return AVERROR_INVALIDDATA;
+
                 /* calculate linear floor value */
                 q = exp((((amplitude*vf->amplitude_offset) /
                           (((1ULL << vf->amplitude_bits) - 1) * sqrt(p + q)))