[FFmpeg-devel] [PATCH] avcodec/av1_parse: Check obu_size

[Michael Niedermayer]

On Sun, Oct 14, 2018 at 11:03:29AM -0300, James Almer wrote:
> On 10/14/2018 10:43 AM, Michael Niedermayer wrote:
> > Fixes: out of array read
> > Fixes: SIGSEGV_get_obu_bit_length_av1_parse
> > 
> > Found-by: keval shah <skeval65 at gmail.com>
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavcodec/av1_parse.h | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/libavcodec/av1_parse.h b/libavcodec/av1_parse.h
> > index 276af33ba9..312d8825e1 100644
> > --- a/libavcodec/av1_parse.h
> > +++ b/libavcodec/av1_parse.h
> > @@ -130,6 +130,9 @@ static inline int parse_obu_header(const uint8_t *buf, int buf_size,
> >      if (get_bits_left(&gb) < 0)
> >          return AVERROR_INVALIDDATA;
> >  
> > +    if (*obu_size > (uint64_t)buf_size - get_bits_count(&gb) / 8)
> > +        return AVERROR_INVALIDDATA;
> > +
> >      *start_pos = get_bits_count(&gb) / 8;
> >  
> >      size = *obu_size + *start_pos;
> 
> Right below this line there's the check
> 
>     if (size > INT_MAX)
>         return AVERROR(ERANGE);
> 
> So i think you could just change it to "size > (int64_t)buf_size" and
> achieve the same effect without adding an extra check.

ive written it a bit overly defensive, not assuming any range limitation
of leb128().
But you are correct, ill simplify and repost it

thx


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