[FFmpeg-devel] [PATCH] avcodec/avcodec: Limit the number of side data elements per packet

[wm4]

On Thu, 11 May 2017 23:27:37 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Thu, May 11, 2017 at 06:54:16PM +0200, wm4 wrote:
> > On Thu, 11 May 2017 13:01:36 +0200
> > Michael Niedermayer <michael at niedermayer.cc> wrote:
> >   
> > > Fixes: 1293/clusterfuzz-testcase-minimized-6054752074858496
> > > 
> > > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
> > > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > > ---
> > >  libavcodec/avcodec.h  | 8 ++++++++
> > >  libavcodec/avpacket.c | 5 ++++-
> > >  2 files changed, 12 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> > > index df6d2bc748..173c083a86 100644
> > > --- a/libavcodec/avcodec.h
> > > +++ b/libavcodec/avcodec.h
> > > @@ -1593,6 +1593,14 @@ enum AVPacketSideDataType {
> > >       * AVContentLightMetadata struct.
> > >       */
> > >      AV_PKT_DATA_CONTENT_LIGHT_LEVEL,
> > > +
> > > +    /**
> > > +     * The number of side data elements (in fact a bit more than it).
> > > +     * This is not part of the public API/ABI in the sense that it may
> > > +     * change when new side data types are added.
> > > +     * This must stay the last enum value.
> > > +     */
> > > +    AV_PKT_DATA_NB,
> > >  };  
> > 
> > OK I guess.
> >   
> > >  #define AV_PKT_DATA_QUALITY_FACTOR AV_PKT_DATA_QUALITY_STATS //DEPRECATED
> > > diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
> > > index 369dd78208..200ba99f34 100644
> > > --- a/libavcodec/avpacket.c
> > > +++ b/libavcodec/avpacket.c
> > > @@ -298,7 +298,7 @@ int av_packet_add_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
> > >      AVPacketSideData *tmp;
> > >      int elems = pkt->side_data_elems;
> > >  
> > > -    if ((unsigned)elems + 1 > INT_MAX / sizeof(*pkt->side_data))
> > > +    if ((unsigned)elems + 1 > FFMIN(INT_MAX / sizeof(*pkt->side_data), AV_PKT_DATA_NB))  
> > 
> > Does the FFMIN and the old expression on the right side still have any
> > function?  
> 
> In practice, no
> In principle, yes, AV_PKT_DATA_NB could be larger than
> INT_MAX / sizeof(*pkt->side_data

That seems extremely unlikely. Feel free to extend the comment on the
new enum item to this extend.

> 
> do you prefer if i remove it ?

Yes.