Re: [FFmpeg-devel] [PATCH v2 1/2] avcodec/vvc_mp4toannexb: check bytes left for nalu_len

[Nuo Mi <nuomi2021@gmail.com>]

On Fri, Feb 9, 2024 at 7:40 PM Andreas Rheinhardt <
andreas.rheinhardt@outlook.com> wrote:

> Nuo Mi:
> > Fixes: fuzzer timeout
> > Fixes:
> 65253/clusterfuzz-testcase-minimized-ffmpeg_BSF_VVC_MP4TOANNEXB_fuzzer-4972412487467008
> >
> > Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> > ---
> >  libavcodec/bsf/vvc_mp4toannexb.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/libavcodec/bsf/vvc_mp4toannexb.c
> b/libavcodec/bsf/vvc_mp4toannexb.c
> > index 25c3726918..36bdae8f49 100644
> > --- a/libavcodec/bsf/vvc_mp4toannexb.c
> > +++ b/libavcodec/bsf/vvc_mp4toannexb.c
> > @@ -155,10 +155,11 @@ static int vvc_extradata_to_annexb(AVBSFContext
> *ctx)
> >          }
> >
> >          for (j = 0; j < cnt; j++) {
> > -            int nalu_len = bytestream2_get_be16(&gb);
> > +            const int nalu_len = bytestream2_get_be16(&gb);
> >
> > -            if (4 + AV_INPUT_BUFFER_PADDING_SIZE + nalu_len >
> > -                SIZE_MAX - new_extradata_size) {
> > +            if (!nalu_len ||
> > +                nalu_len > bytestream2_get_bytes_left(&gb) ||
> > +                4 + AV_INPUT_BUFFER_PADDING_SIZE + nalu_len > SIZE_MAX
> - new_extradata_size) {
> >                  ret = AVERROR_INVALIDDATA;
> >                  goto fail;
> >              }
>
> What about growing the packet?
>
Hi Andreas,
Do you mean growing the packet only once for all nalus?
However, this would change the original behavior and result in more
duplicate code between the HEVC and VVC implementations.
I can do it, but I'll refactor duplications to h2656_mp4toannexb.c first.
Do you think that's okay?
Thank you


> - Andreas
>
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