[FFmpeg-cvslog] avcodec/ffwavesynth: Avoid signed integer overflow in phi_at()

[Michael Niedermayer]

ffmpeg | branch: release/4.4 | Michael Niedermayer <michael at niedermayer.cc> | Fri Mar  5 20:27:50 2021 +0100| [e42efdce95d0d849bff35bb4ad62babbcc0926a4] | committer: Michael Niedermayer

avcodec/ffwavesynth: Avoid signed integer overflow in phi_at()

Fixes: signed integer overflow: 2314885530818453536 - -9070214327174160352 cannot be represented in type 'long'
Fixes: 31000/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFWAVESYNTH_fuzzer-6558389742206976

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 be08b84f8bb7acc0c45800c7f488399327a22961)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=e42efdce95d0d849bff35bb4ad62babbcc0926a4
---

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

diff --git a/libavcodec/ffwavesynth.c b/libavcodec/ffwavesynth.c
index 7e7e1f6954..3f982d07cf 100644
--- a/libavcodec/ffwavesynth.c
+++ b/libavcodec/ffwavesynth.c
@@ -188,7 +188,7 @@ static uint64_t frac64(uint64_t a, uint64_t b)
 
 static uint64_t phi_at(struct ws_interval *in, int64_t ts)
 {
-    uint64_t dt = ts - in->ts_start;
+    uint64_t dt = ts - (uint64_t)in->ts_start;
     uint64_t dt2 = dt & 1 ? /* dt * (dt - 1) / 2 without overflow */
                    dt * ((dt - 1) >> 1) : (dt >> 1) * (dt - 1);
     return in->phi0 + dt * in->dphi0 + dt2 * in->ddphi;