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avformat/utils: Do not assume duration is non negative in compute_pkt_fields() 

Several subtitle demuxers set negative durations

Fixes: signed integer overflow: 9223372036854775807 - -1 cannot be represented in type 'long'
Fixes: 16925/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5766519790764032

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2019-09-05 23:06:21 +02:00
parent c7ccbf40ed
commit 72db18e929
1 changed files with 4 additions and 4 deletions
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8
libavformat/utils.c
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@ -1299,7 +1299,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
}
duration = av_mul_q((AVRational) {pkt->duration, 1}, st->time_base);
if (pkt->duration == 0) {
if (pkt->duration <= 0) {
ff_compute_frame_duration(s, &num, &den, st, pc, pkt);
if (den && num) {
duration = (AVRational) {num, den};
@ -1310,7 +1310,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
}
}
if (pkt->duration != 0 && (s->internal->packet_buffer || s->internal->parse_queue))
if (pkt->duration > 0 && (s->internal->packet_buffer || s->internal->parse_queue))
update_initial_durations(s, st, pkt->stream_index, pkt->duration);
/* Correct timestamps with byte offset if demuxers only have timestamps
@ -1370,7 +1370,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
* by knowing the future. */
} else if (pkt->pts != AV_NOPTS_VALUE ||
pkt->dts != AV_NOPTS_VALUE ||
pkt->duration ) {
pkt->duration > 0 ) {
/* presentation is not delayed : PTS and DTS are the same */
if (pkt->pts == AV_NOPTS_VALUE)
@ -1380,7 +1380,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
if (pkt->pts == AV_NOPTS_VALUE)
pkt->pts = st->cur_dts;
pkt->dts = pkt->pts;
if (pkt->pts != AV_NOPTS_VALUE)
if (pkt->pts != AV_NOPTS_VALUE && duration.num >= 0)
st->cur_dts = av_add_stable(st->time_base, pkt->pts, duration, 1);
}
}