[FFmpeg-devel] [PATCH 5/5] avcodec/hevc/ps: use unsigned shift

[James Almer]

On 8/16/2024 8:15 PM, Michael Niedermayer wrote:
> Fixes: left shift of 1 by 31 places cannot be represented in type 'int'
> Fixes: 70726/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-6149928703819776
> 
> 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/hevc/ps.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/hevc/ps.c b/libavcodec/hevc/ps.c
> index 80ac35a7dbf..cd5ece72b0a 100644
> --- a/libavcodec/hevc/ps.c
> +++ b/libavcodec/hevc/ps.c
> @@ -1101,7 +1101,7 @@ int ff_hevc_parse_sps(HEVCSPS *sps, GetBitContext *gb, unsigned int *sps_id,
>           sps->used_by_curr_pic_lt = 0;
>           for (i = 0; i < sps->num_long_term_ref_pics_sps; i++) {
>               sps->lt_ref_pic_poc_lsb_sps[i]       = get_bits(gb, sps->log2_max_poc_lsb);
> -            sps->used_by_curr_pic_lt            |= get_bits1(gb) * (1 << i);
> +            sps->used_by_curr_pic_lt            |= get_bits1(gb) * (1U << i);

Why not just get_bits1(gb) << i? get_bits1() returns an unsigned int 
(Either 0 or 1), so no chances for a left shift of negative number.