[FFmpeg-cvslog] avformat/jacosubdec: Fix overflow in get_shift()

[Michael Niedermayer]

ffmpeg | branch: release/5.1 | Michael Niedermayer <michael at niedermayer.cc> | Sat Sep 17 22:55:24 2022 +0200| [740a71b58362e536f43b51ed3c66ae8339f2554d] | committer: Michael Niedermayer

avformat/jacosubdec: Fix overflow in get_shift()

Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_JACOSUB_fuzzer-6722544461283328
Fixes: signed integer overflow: 48214448 * 60 cannot be represented in type 'int'

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 b1a68127bbcd3d638363fa0249982c494e87c9e2)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=740a71b58362e536f43b51ed3c66ae8339f2554d
---

 libavformat/jacosubdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/jacosubdec.c b/libavformat/jacosubdec.c
index 0ee4820f62..61b1316dc9 100644
--- a/libavformat/jacosubdec.c
+++ b/libavformat/jacosubdec.c
@@ -144,7 +144,7 @@ static int get_shift(int timeres, const char *buf)
     ret = 0;
     switch (n) {
     case 4:
-        ret = sign * (((int64_t)a*3600 + b*60 + c) * timeres + d);
+        ret = sign * (((int64_t)a*3600 + (int64_t)b*60 + c) * timeres + d);
         break;
     case 3:
         ret = sign * ((         (int64_t)a*60 + b) * timeres + c);