[FFmpeg-cvslog] avcodec/ffwavesynth: Fix integer overflow in computation of ddphi

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Sun Mar 15 18:25:56 2020 +0100| [c00a5fc71f144b5f70efcefb4910b8afd53c274a] | committer: Michael Niedermayer

avcodec/ffwavesynth: Fix integer overflow in computation of ddphi

Fixes: signed integer overflow: 1302123111085380114 - -8319005078741256972 cannot be represented in type 'long'
Fixes: 20991/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFWAVESYNTH_fuzzer-5148554161291264

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Nicolas George <george at nsup.org>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit c85bf1631823e9089e59a474d5c6c0efc708c507)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c00a5fc71f144b5f70efcefb4910b8afd53c274a
---

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

diff --git a/libavcodec/ffwavesynth.c b/libavcodec/ffwavesynth.c
index b9c63abb8d..998e1a4ad6 100644
--- a/libavcodec/ffwavesynth.c
+++ b/libavcodec/ffwavesynth.c
@@ -281,7 +281,7 @@ static int wavesynth_parse_extradata(AVCodecContext *avc)
                 dphi1 = frac64(f1, (int64_t)avc->sample_rate << 16);
                 dphi2 = frac64(f2, (int64_t)avc->sample_rate << 16);
                 in->dphi0 = dphi1;
-                in->ddphi = (dphi2 - dphi1) / dt;
+                in->ddphi = (int64_t)(dphi2 - (uint64_t)dphi1) / dt;
                 if (phi & 0x80000000) {
                     phi &= ~0x80000000;
                     if (phi >= i)