[FFmpeg-devel] [PATCH 1/6] avcodec/cbs: sei_3d_reference_displays_info uses length 0 elements

[James Almer]

On 7/31/2024 4:54 PM, Michael Niedermayer wrote:
> Fixes: 70458/clusterfuzz-testcase-minimized-ffmpeg_BSF_TRACE_HEADERS_fuzzer-5259339779080192
> Fixes: Assertion width > 0 && width <= 32 failed at libavcodec/cbs.c:608
> 
> 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/cbs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c
> index b26e39eab4d..dcbc86a5f7d 100644
> --- a/libavcodec/cbs.c
> +++ b/libavcodec/cbs.c
> @@ -605,7 +605,7 @@ static av_always_inline int cbs_read_unsigned(CodedBitstreamContext *ctx,
>   
>       CBS_TRACE_READ_START();
>   
> -    av_assert0(width > 0 && width <= 32);
> +    av_assert0(width >= 0 && width <= 32);

No, sei_3d_reference_displays_info should instead not attempt to read 
from the bitstream when width is 0.

I'll send a patch for this later.

>   
>       if (get_bits_left(gbc) < width) {
>           av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid value at "