Re: [FFmpeg-devel] [PATCH 4/5] avcodec/sga: Check non constant init_get_bits8()

[Michael Niedermayer <michael@niedermayer.cc>]

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On Fri, May 17, 2024 at 09:53:21AM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: CID1473562 Unchecked return value
> > Fixes: CID1473592 Unchecked return value
> > 
> > Sponsored-by: Sovereign Tech Fund
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/sga.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/libavcodec/sga.c b/libavcodec/sga.c
> > index 0f42cf912b2..aca941e057e 100644
> > --- a/libavcodec/sga.c
> > +++ b/libavcodec/sga.c
> > @@ -254,11 +254,14 @@ static int decode_palmapdata(AVCodecContext *avctx)
> >      const int bits = (s->nb_pal + 1) / 2;
> >      GetByteContext *gb = &s->gb;
> >      GetBitContext pm;
> > +    int ret;
> >  
> >      bytestream2_seek(gb, s->palmapdata_offset, SEEK_SET);
> >      if (bytestream2_get_bytes_left(gb) < s->palmapdata_size)
> >          return AVERROR_INVALIDDATA;
> > -    init_get_bits8(&pm, gb->buffer, s->palmapdata_size);
> > +    ret = init_get_bits8(&pm, gb->buffer, s->palmapdata_size);
> > +    if (ret < 0)
> > +        return ret;
> >  
> >      for (int y = 0; y < s->tiles_h; y++) {
> >          uint8_t *dst = s->palmapindex_data + y * s->tiles_w;
> > @@ -277,11 +280,14 @@ static int decode_tiledata(AVCodecContext *avctx)
> >      SGAVideoContext *s = avctx->priv_data;
> >      GetByteContext *gb = &s->gb;
> >      GetBitContext tm;
> > +    int ret;
> >  
> >      bytestream2_seek(gb, s->tiledata_offset, SEEK_SET);
> >      if (bytestream2_get_bytes_left(gb) < s->tiledata_size)
> >          return AVERROR_INVALIDDATA;
> > -    init_get_bits8(&tm, gb->buffer, s->tiledata_size);
> > +    ret = init_get_bits8(&tm, gb->buffer, s->tiledata_size);
> > +    if (ret < 0)
> > +        return ret;
> >  
> >      for (int n = 0; n < s->nb_tiles; n++) {
> >          uint8_t *dst = s->tileindex_data + n * 64;
> 
> Both of these can not fail and could be checked via av_assert1:
> palmapdata_size is given by (s->tiles_w * s->tiles_h * ((s->nb_pal + 1)
> / 2) + 7) / 8 with tiles_w and tiles_h being in the 0..255 range and
> nb_pal being in the 0..4 range.
> tiledata_size is given by s->nb_tiles * 32; nb_tiles fits in 16 bits (it
> is either read via AV_RB16 or is given as the product of tiles_h *
> tiles_w, both of which are read from simple uint8_t.

ill use av_assert1()

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus

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