[FFmpeg-cvslog] avformat/subtitles: Check pts difference before use

[Michael Niedermayer]

ffmpeg | branch: release/4.4 | Michael Niedermayer <michael at niedermayer.cc> | Sun Apr 25 19:49:14 2021 +0200| [8bddb1d3ef8b8c91111263da64b5e606dca5cd96] | committer: Michael Niedermayer

avformat/subtitles: Check pts difference before use

Fixes: signed integer overflow: 0 - -9223372036854775808 cannot be represented in type 'long'
Fixes: 29102/clusterfuzz-testcase-minimized-ffmpeg_dem_MPL2_fuzzer-6747053545881600

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 e7a990164f67108e99ec5adb8b2d636cd4147715)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8bddb1d3ef8b8c91111263da64b5e606dca5cd96
---

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

diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
index 05c07cd852..6368ec74f9 100644
--- a/libavformat/subtitles.c
+++ b/libavformat/subtitles.c
@@ -206,7 +206,7 @@ void ff_subtitles_queue_finalize(void *log_ctx, FFDemuxSubtitlesQueue *q)
           q->sort == SUB_SORT_TS_POS ? cmp_pkt_sub_ts_pos
                                      : cmp_pkt_sub_pos_ts);
     for (i = 0; i < q->nb_subs; i++)
-        if (q->subs[i]->duration < 0 && i < q->nb_subs - 1)
+        if (q->subs[i]->duration < 0 && i < q->nb_subs - 1 && q->subs[i + 1]->pts - (uint64_t)q->subs[i]->pts <= INT64_MAX)
             q->subs[i]->duration = q->subs[i + 1]->pts - q->subs[i]->pts;
 
     if (!q->keep_duplicates)