avformat/matroskadec: Error out if a timestamp is beyond duration

Maybe timestamp / duration validity should be checked earlier

Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_WEBM_DASH_MANIFEST_fuzzer-6586894739177472
Fixes: signed integer overflow: 0 - -9223372036854775808 cannot be represented in type 'long'

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/matroskadec.c

@@ -4009,7 +4009,8 @@ typedef struct {
 
 /* This function searches all the Cues and returns the CueDesc corresponding to
  * the timestamp ts. Returned CueDesc will be such that start_time_ns <= ts <
- * end_time_ns. All 4 fields will be set to -1 if ts >= file's duration.
+ * end_time_ns. All 4 fields will be set to -1 if ts >= file's duration or
+ * if an error occurred.
  */
 static CueDesc get_cue_desc(AVFormatContext *s, int64_t ts, int64_t cues_start) {
     MatroskaDemuxContext *matroska = s->priv_data;
@@ -4028,6 +4029,8 @@ static CueDesc get_cue_desc(AVFormatContext *s, int64_t ts, int64_t cues_start)
         }
     }
     --i;
+    if (index_entries[i].timestamp > matroska->duration)
+        return (CueDesc) {-1, -1, -1, -1};
     cue_desc.start_time_ns = index_entries[i].timestamp * matroska->time_scale;
     cue_desc.start_offset = index_entries[i].pos - matroska->segment_start;
     if (i != nb_index_entries - 1) {