[FFmpeg-devel] [PATCH 1/2] lavc/aac_ac3_parser: fix the potential overflow

[Anton Khirnov]

Quoting Jun Zhao (2020-06-29 15:23:10)
> From: Jun Zhao <barryjzhao at tencent.com>
> 
> Fix the potential overflow.
> 
> Suggested-by: Alexander Strasser <eclipse7 at gmx.net>
> Signed-off-by: Jun Zhao <barryjzhao at tencent.com>
> ---
>  libavcodec/aac_ac3_parser.c         | 9 +++++----
>  libavcodec/aac_ac3_parser.h         | 4 ++--
>  tests/ref/fate/adtstoasc_ticket3715 | 2 +-
>  3 files changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/libavcodec/aac_ac3_parser.c b/libavcodec/aac_ac3_parser.c
> index 0746798..b26790d 100644
> --- a/libavcodec/aac_ac3_parser.c
> +++ b/libavcodec/aac_ac3_parser.c
> @@ -98,11 +98,12 @@ get_next:
>          }
>  
>          /* Calculate the average bit rate */
> -        s->frame_number++;
>          if (avctx->codec_id != AV_CODEC_ID_EAC3) {
> -            avctx->bit_rate =
> -                (s->last_bit_rate * (s->frame_number -1) + s->bit_rate)/s->frame_number;
> -            s->last_bit_rate = avctx->bit_rate;
> +            if (s->frame_number < UINT64_MAX) {
> +                s->frame_number++;
> +                s->last_bit_rate += (s->bit_rate - s->last_bit_rate)/s->frame_number;
> +                avctx->bit_rate = (int64_t)llround(s->last_bit_rate);
> +            }
>          }
>      }
>  
> diff --git a/libavcodec/aac_ac3_parser.h b/libavcodec/aac_ac3_parser.h
> index b04041f..c53d16f 100644
> --- a/libavcodec/aac_ac3_parser.h
> +++ b/libavcodec/aac_ac3_parser.h
> @@ -55,8 +55,8 @@ typedef struct AACAC3ParseContext {
>      uint64_t state;
>  
>      int need_next_header;
> -    int frame_number;
> -    int last_bit_rate;
> +    uint64_t frame_number;
> +    double last_bit_rate;

This won't give the same result on all platforms anymore.

-- 
Anton Khirnov