avformat/lrcdec: Clip timestamps

Fixes: signed integer overflow: 7111111111111531010 - -7335632962598013506 cannot be represented in type 'long'
Fixes: 26463/clusterfuzz-testcase-minimized-ffmpeg_dem_LRC_fuzzer-6015558333759488

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

libavformat/lrcdec.c

@@ -185,6 +185,8 @@ static int lrc_read_header(AVFormatContext *s)
                    sscanf(comma_offset + 1, "%"SCNd64, &lrc->ts_offset) != 1) {
                     av_dict_set(&s->metadata, line.str + 1, comma_offset + 1, 0);
                 }
+                lrc->ts_offset = av_clip64(lrc->ts_offset, INT64_MIN/4, INT64_MAX/4);
+
                 *comma_offset = ':';
                 *right_bracket_offset = ']';
             }
@@ -198,6 +200,7 @@ static int lrc_read_header(AVFormatContext *s)
 
             while((ts_stroffset_incr = read_ts(line.str + ts_stroffset,
                                                &ts_start)) != 0) {
+                ts_start = av_clip64(ts_start, INT64_MIN/4, INT64_MAX/4);
                 ts_stroffset += ts_stroffset_incr;
                 sub = ff_subtitles_queue_insert(&lrc->q, line.str + ts_strlength,
                                                 line.len - ts_strlength, 0);