[FFmpeg-devel] [PATCH 2/3] avcodec/smacker: Check remaining bits in SMK_BLK_FULL

[Michael Niedermayer]

On Mon, Oct 05, 2020 at 03:24:08AM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: out of array access
> > Fixes: 26047/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SMACKER_fuzzer-5083031667474432
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavcodec/smacker.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c
> > index 813eb862c0..6b1faec09e 100644
> > --- a/libavcodec/smacker.c
> > +++ b/libavcodec/smacker.c
> > @@ -448,6 +448,8 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
> >          case SMK_BLK_FULL:
> >              mode = 0;
> >              if(avctx->codec_tag == MKTAG('S', 'M', 'K', '4')) { // In case of Smacker v4 we have three modes
> > +                if (get_bits_left(&gb) < 1)
> > +                    return AVERROR_INVALIDDATA;
> >                  if(get_bits1(&gb)) mode = 1;
> >                  else if(get_bits1(&gb)) mode = 2;
> >              }
> > 
> LGTM.

will apply


> (This is a file in which the type and the full tree consists of only one
> entry (so that smk_get_code() never checks for overreads), isn't it? I
> have to admit to have overlooked this edge case.)

possibly so, id have to recheck

thx

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

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable
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