Re: [FFmpeg-devel] [PATCH 2/2] avformat/subtitles: Check for NOPTS in ff_subtitles_queue_finalize()

[Michael Niedermayer]

On Tue, Jun 23, 2020 at 02:08:44PM +0200, Nicolas George wrote:
> Michael Niedermayer (12020-06-23):
> > Fixes; signed integer overflow: 1 - -9223372036854775808 cannot be 
> > represented in type 'long'
> > Fixes: 
> > 23490/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5133490093031424
> > 
> > Found-by: continuous fuzzing process 
> > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> > ---
> >  libavformat/subtitles.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
> > index ad7f68938e..ccab80391f 100644
> > --- a/libavformat/subtitles.c
> > +++ b/libavformat/subtitles.c
> > @@ -202,7 +202,7 @@ void ff_subtitles_queue_finalize(void *log_ctx, 
> > FFDemuxSubtitlesQueue *q)
> >            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)
> > +        if (q->subs[i].duration < 0 && i < q->nb_subs - 1 && 
> > q->subs[i].pts != AV_NOPTS_VALUE)
> >              q->subs[i].duration = q->subs[i + 1].pts - q->subs[i].pts;
> >  
> >      if (!q->keep_duplicates)
> 
> Having no PTS at this point makes no sense. We should examine why it
> arrived there. 

it comes from microdvddec in this case, it can be fixed for example
with the following: (i do not know if these are all cases which can
generate this)

commit 06eff32c6e4100b70a3a215a0756580a6fa124b5 (HEAD -> master)
Author: Michael Niedermayer <mich...@niedermayer.cc>
Date:   Tue Jun 23 01:43:14 2020 +0200

    iavformat/microdvddec: Skip NOPTS values
    
    Fixes; signed integer overflow: 1 - -9223372036854775808 cannot be 
represented in type 'long'
    Fixes: 
23490/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5133490093031424
    
    Found-by: continuous fuzzing process 
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
    Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>

diff --git a/libavformat/microdvddec.c b/libavformat/microdvddec.c
index 8759200f88..1f871b2518 100644
--- a/libavformat/microdvddec.c
+++ b/libavformat/microdvddec.c
@@ -94,6 +94,7 @@ static int microdvd_read_header(AVFormatContext *s)
         int64_t pos = avio_tell(s->pb);
         int len = ff_get_line(s->pb, line_buf, sizeof(line_buf));
         char *line = line_buf;
+        int64_t pts;
 
         if (!strncmp(line, bom, 3))
             line += 3;
@@ -137,13 +138,16 @@ static int microdvd_read_header(AVFormatContext *s)
         SKIP_FRAME_ID;
         if (!*p)
             continue;
+        pts = get_pts(line);
+        if (pts == AV_NOPTS_VALUE)
+            continue;
         sub = ff_subtitles_queue_insert(&microdvd->q, p, strlen(p), 0);
         if (!sub) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
         sub->pos = pos;
-        sub->pts = get_pts(line);
+        sub->pts = pts;
         sub->duration = get_duration(line);
     }
     ff_subtitles_queue_finalize(s, &microdvd->q);





> Can you share the test case?

Ill send you the file privatly

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire

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