[FFmpeg-devel] [PATCH] indeo3: add out-of-buffer write check

[Stefano Sabatini]

On date Wednesday 2011-05-18 07:53:31 +0200, Reimar Döffinger encoded:
> 
> 
> On 17 May 2011, at 22:30, Stefano Sabatini <stefano.sabatini-lala at poste.it> wrote:
> 
> > Prevent out-of-buffer reads. In particular fix smclocki32.avi.1.1
> > crash, fix trac issue #114, roundup issue #1482.
> > ---
> > libavcodec/indeo3.c |    3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> > 
> > diff --git a/libavcodec/indeo3.c b/libavcodec/indeo3.c
> > index fb33a7c..37124e4 100644
> > --- a/libavcodec/indeo3.c
> > +++ b/libavcodec/indeo3.c
> > @@ -208,6 +208,7 @@ static void iv_Decode_Chunk(Indeo3DecodeContext *s,
> >     int *width_tbl, width_tbl_arr[10];
> >     const signed char *ref_vectors;
> >     uint8_t *cur_frm_pos, *ref_frm_pos, *cp, *cp2;
> > +    uint8_t *cur_end = cur + width*height + width;
> >     uint32_t *cur_lp, *ref_lp;
> >     const uint32_t *correction_lp[2], *correctionloworder_lp[2], *correctionhighorder_lp[2];
> >     uint8_t *correction_type_sp[2];
> > @@ -354,6 +355,8 @@ static void iv_Decode_Chunk(Indeo3DecodeContext *s,
> >                             k = *buf1++;
> >                             cur_lp = ((uint32_t *)cur_frm_pos) + width_tbl[lp2];
> >                             ref_lp = ((uint32_t *)ref_frm_pos) + width_tbl[lp2];
> > +                            if ((uint8_t *)cur_lp >= cur_end)
> > +                                break;
> 
> Not sure it matters, but this could still overread with cur_lp == cur_end - 1

In practice cur_lp is always a pointer to uint32_t, so is is always
incremented by 4 units. A better solution would involve to fix the
code logic, but that would require a better understanding of the
codec.
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