Re: [FFmpeg-devel] [PATCH 2/4] avformat/mxfdec: Check count in mxf_read_strong_ref_array()

[Michael Niedermayer <michael@niedermayer.cc>]

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On Mon, Mar 14, 2022 at 08:19:51PM +0100, Tomas Härdin wrote:
> sön 2022-03-13 klockan 00:52 +0100 skrev Michael Niedermayer:
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavformat/mxfdec.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> > index b85c10bf19..d7cdd22c8a 100644
> > --- a/libavformat/mxfdec.c
> > +++ b/libavformat/mxfdec.c
> > @@ -932,7 +932,13 @@ static int mxf_read_cryptographic_context(void
> > *arg, AVIOContext *pb, int tag, i
> >  
> >  static int mxf_read_strong_ref_array(AVIOContext *pb, UID **refs,
> > int *count)
> >  {
> > -    *count = avio_rb32(pb);
> > +    unsigned c = avio_rb32(pb);
> 
> not uint32_t?

we dont need an exact length variable here


> 
> > +
> > +    //avio_read() used int
> > +    if (c > INT_MAX / sizeof(UID))
> > +        return AVERROR_PATCHWELCOME;
> > +    *count = c;
> > +
> 
> This should already be caught by av_calloc(), no?

the API as in the documentation of av_calloc() does not gurantee
this. Its bad practice if we write code that depends on some implementation
of some code in a diferent module/lib

thx

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

Does the universe only have a finite lifespan? No, its going to go on
forever, its just that you wont like living in it. -- Hiranya Peiri

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