Re: [FFmpeg-devel] [PATCH 1/4] avcodec/vp9_superframe_split_bsf: Check in size

[James Almer <jamrial@gmail.com>]

On 3/12/2022 8:52 PM, Michael Niedermayer wrote:
> Fixes: Out of array read
> Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   libavcodec/vp9_superframe_split_bsf.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
> index ed0444561a..6af555c078 100644
> --- a/libavcodec/vp9_superframe_split_bsf.c
> +++ b/libavcodec/vp9_superframe_split_bsf.c
> @@ -51,6 +51,11 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
>               return ret;
>           in = s->buffer_pkt;
>   
> +        if (in->size == 0) {

!in->size

> +            ret = AVERROR_INVALIDDATA;
> +            goto fail;
> +        }
> +
>           marker = in->data[in->size - 1];

Do we want to abort on in->data && !in->size, or just pass the packet 
through?
I'm partial to the latter, so it would mean initializing marker to 0 and 
check instead for in->size before setting marker, so the check below 
fails and the packet is just passed through.

Not sure what others think about it.

>           if ((marker & 0xe0) == 0xc0) {
>               int length_size = 1 + ((marker >> 3) & 0x3);
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