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

[Michael Niedermayer]

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

do you prefer if i remove it ?

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

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
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