#11388: Overflow in start_time_realtime calculation in rtsp.c
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Reporter: | Type: defect
IncrediBlame |
Status: new | Priority: normal
Component: ffmpeg | Version: git-
Keywords: | master
start_time_realtime RTSP RTCP | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug:
start_time_realtime calculation was changed in realease/7.1 branch:
[https://github.com/FFmpeg/FFmpeg/blob/bb85423142103d694d97bad1967bd3dc55440e71/libavformat/rtsp.c#L2323]
This is causing overflow, as av_rescale treats its args as int64_t, but
rtpctx->first_rtcp_ntp_time used in calculation is uint64_t.
Previous version worked, because the arg was shifted by an offset before
used by av_rescale, but now shift is done after calculation.
How to reproduce:
{{{
1. Add pprintf after calculation above.
2. Build ffmpeg.
2. Run
% ffmpeg -i some_rtsp_source -c copy abc.mp4
3. If rtsp source sends RTCP SR the code will eventually be hit, but sets
the timestamp to some negative number.
}}}
Potential fix:
{{{
s->start_time_realtime = av_rescale (rtpctx->first_rtcp_ntp_time >> 2,
1000000, 1LL << 30) - NTP_OFFSET_US;
}}}
should stop the overflow.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11388>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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