[FFmpeg-devel] [PATCH 3/4] avformat/subtitles: Check nb_subs in ff_subtitles_queue_finalize()

[Michael Niedermayer]

Fixes: null pointer dereference
Fixes: 17828/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5645915116797952

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavformat/subtitles.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
index 659c99d1cf..ded1b910c5 100644
--- a/libavformat/subtitles.c
+++ b/libavformat/subtitles.c
@@ -194,9 +194,10 @@ void ff_subtitles_queue_finalize(void *log_ctx, FFDemuxSubtitlesQueue *q)
 {
     int i;
 
-    qsort(q->subs, q->nb_subs, sizeof(*q->subs),
-          q->sort == SUB_SORT_TS_POS ? cmp_pkt_sub_ts_pos
-                                     : cmp_pkt_sub_pos_ts);
+    if (q->nb_subs)
+        qsort(q->subs, q->nb_subs, sizeof(*q->subs),
+              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)
             q->subs[i].duration = q->subs[i + 1].pts - q->subs[i].pts;
-- 
2.23.0