[FFmpeg-devel] [PATCH 1/5] avcodec/pcm_rechunk_bsf: unref packet before putting a new one in

[Michael Niedermayer]

On Sun, Apr 16, 2023 at 07:57:00PM -0300, James Almer wrote:
> On 4/16/2023 7:25 PM, Michael Niedermayer wrote:
> > Fixes: memleak
> > Fixes: 45982/clusterfuzz-testcase-minimized-ffmpeg_BSF_PCM_RECHUNK_fuzzer-5562089618407424
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >   libavcodec/pcm_rechunk_bsf.c | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/libavcodec/pcm_rechunk_bsf.c b/libavcodec/pcm_rechunk_bsf.c
> > index 108d9e90b99..3f43934fe9a 100644
> > --- a/libavcodec/pcm_rechunk_bsf.c
> > +++ b/libavcodec/pcm_rechunk_bsf.c
> > @@ -153,6 +153,7 @@ static int rechunk_filter(AVBSFContext *ctx, AVPacket *pkt)
> >               }
> >           }
> > +        av_packet_unref(s->in_pkt);
> 
> This could be pointing to a bug in the above code, and unreffing here like
> this would result in data loss.
> 
> Does the following change also fix the memleak?
> 
> > diff --git a/libavcodec/pcm_rechunk_bsf.c b/libavcodec/pcm_rechunk_bsf.c
> > index 108d9e90b9..032f914916 100644
> > --- a/libavcodec/pcm_rechunk_bsf.c
> > +++ b/libavcodec/pcm_rechunk_bsf.c
> > @@ -151,7 +151,8 @@ static int rechunk_filter(AVBSFContext *ctx, AVPacket *pkt)
> >                  av_packet_move_ref(pkt, s->in_pkt);
> >                  return send_packet(s, nb_samples, pkt);
> >              }
> > -        }
> > +        } else
> > +            av_packet_unref(s->in_pkt);
> > 
> >          ret = ff_bsf_get_packet_ref(ctx, s->in_pkt);
> >          if (ret == AVERROR_EOF && s->out_pkt->size) {
> 
> If it does then a zero sized packet with either only side data or that went
> through the av_packet_make_refcounted() in av_bsf_send_packet() that left it
> with an allocated padding buffer was fed to this bsf.

yes this works too
and this memleak is open since a year, its the 2nd time i submited this
patch, last time the discussions didnt lead to any consensus on what to do
I hope this time some fix from someone ends up in git

thx

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

The real ebay dictionary, page 2
"100% positive feedback" - "All either got their money back or didnt complain"
"Best seller ever, very honest" - "Seller refunded buyer after failed scam"
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20230417/2149111c/attachment.sig>