[FFmpeg-devel] [PATCH 4/4] avcodec/hqx: Check the input data against the image size

[Paul B Mahol]

On 7/23/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
> On Mon, Jul 22, 2019 at 08:20:54AM +0200, Paul B Mahol wrote:
>> On 7/21/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
>> > On Sun, Jul 21, 2019 at 10:48:26AM +0200, Paul B Mahol wrote:
>> >> On 7/21/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
>> >> > Fixes: Timeout (22 -> 7 sec)
>> >> > Fixes:
>> >> > 15173/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HQX_fuzzer-5662556846292992
>> >> >
>> >> > 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/hqx.c | 4 ++++
>> >> >  1 file changed, 4 insertions(+)
>> >> >
>> >> > diff --git a/libavcodec/hqx.c b/libavcodec/hqx.c
>> >> > index bc24ba91d1..8639d77a41 100644
>> >> > --- a/libavcodec/hqx.c
>> >> > +++ b/libavcodec/hqx.c
>> >> > @@ -471,6 +471,10 @@ static int hqx_decode_frame(AVCodecContext
>> >> > *avctx,
>> >> > void
>> >> > *data,
>> >> >      avctx->height              = ctx->height;
>> >> >      avctx->bits_per_raw_sample = 10;
>> >> >
>> >> > +    if (avctx->coded_width / 16 * (avctx->coded_height / 16) *
>> >> > +        (100 - avctx->discard_damaged_percentage) / 100 > 8LL *
>> >> > avpkt->size)
>> >> > +        return AVERROR_INVALIDDATA;
>> >>
>> >> Why just this change and not something better?
>> >
>> > What would you prefer exactly ?
>>
>> Something that works with pure black video.
>
> Can you share the failing video file ?
> I thought theres a minimum size of 1 vlc code (2 bit seem the smallest)
> per 16x16 block. But quite possibly i might have missed something
>

This is very disappointing. There is no freely available encoder for HQX.
And the one who commits stuff need to make sure it does not introduce
regressions.


> Thanks
>
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> The educated differ from the uneducated as much as the living from the
> dead. -- Aristotle
>