[FFmpeg-devel] [PATCH 3/4] avformat/subtitles: Check nb_subs in ff_subtitles_queue_finalize()

[Michael Niedermayer]

On Sun, Oct 06, 2019 at 05:43:00AM +0000, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: null pointer dereference
> > Fixes: 17828/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5645915116797952
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavformat/subtitles.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
> > index 659c99d1cf..ded1b910c5 100644
> > --- a/libavformat/subtitles.c
> > +++ b/libavformat/subtitles.c
> > @@ -194,9 +194,10 @@ void ff_subtitles_queue_finalize(void *log_ctx, FFDemuxSubtitlesQueue *q)
> >  {
> >      int i;
> >  
> > -    qsort(q->subs, q->nb_subs, sizeof(*q->subs),
> > -          q->sort == SUB_SORT_TS_POS ? cmp_pkt_sub_ts_pos
> > -                                     : cmp_pkt_sub_pos_ts);
> > +    if (q->nb_subs)
> > +        qsort(q->subs, q->nb_subs, sizeof(*q->subs),
> > +              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)
> >              q->subs[i].duration = q->subs[i + 1].pts - q->subs[i].pts;
> > 
> Why not simply use
> if (!q->nb_subs)
>     return;
> After all, neither the loop nor drop_dups() does anything if there are
> no subs. And you should mention ticket #8147.

ok will push with these changes

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20191006/19b01066/attachment.sig>