[FFmpeg-devel] [PATCH] avformat/aviobuf: Delay buffer downsizing until asserts are met

[Michael Niedermayer]

On Mon, Jun 17, 2019 at 11:12:00PM +0000, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: Assertion failure
> > Fixes: 15151/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5757079496687616
> > 
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavformat/aviobuf.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
> > index 5a33f82950..6a5cd97b0a 100644
> > --- a/libavformat/aviobuf.c
> > +++ b/libavformat/aviobuf.c
> > @@ -570,7 +570,7 @@ static void fill_buffer(AVIOContext *s)
> >      }
> >  
> >      /* make buffer smaller in case it ended up large after probing */
> > -    if (s->read_packet && s->orig_buffer_size && s->buffer_size > s->orig_buffer_size) {
> > +    if (s->read_packet && s->orig_buffer_size && s->buffer_size > s->orig_buffer_size && len >= s->orig_buffer_size) {
> >          if (dst == s->buffer && s->buf_ptr != dst) {
> >              int ret = ffio_set_buf_size(s, s->orig_buffer_size);
> >              if (ret < 0)
> > @@ -578,7 +578,6 @@ static void fill_buffer(AVIOContext *s)
> >  
> >              s->checksum_ptr = dst = s->buffer;
> >          }
> > -        av_assert0(len >= s->orig_buffer_size);
> >          len = s->orig_buffer_size;
> >      }
> >  
> > 
> I just noticed that ticket #7094 is about this assert. Could you test
> whether everything works fine with your fix applied (and then mention
> said this ticket in the commit message)?

The ticket does not contain a full testcase, just a code snippet,
and the person reporting the issue has not yet replied
I suggest we apply this fix with a "May fix Ticket7094"


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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