[FFmpeg-devel] [PATCH 2/4] cbs_mpeg2: Improve checks for invalid values

[James Almer]

On 4/21/2019 11:04 AM, Andreas Rheinhardt wrote:
> horizontal/vertical_size_value (containing the twelve least significant
> bits of the frame size) mustn't be zero according to the specifications;
> and the value 0 is forbidden for the colour_description elements.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavcodec/cbs_mpeg2.c                 | 17 ++++++++++-------
>  libavcodec/cbs_mpeg2_syntax_template.c | 10 +++++-----
>  2 files changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
> index 41f16bbabf..066ea83970 100644
> --- a/libavcodec/cbs_mpeg2.c
> +++ b/libavcodec/cbs_mpeg2.c
> @@ -42,19 +42,22 @@
>  
>  #define ui(width, name) \
>          xui(width, name, current->name, 0)
> +#define uir(width, name, range_min, range_max) \
> +        xuir(width, name, current->name, range_min, range_max, 0)
>  #define uis(width, name, subs, ...) \
>          xui(width, name, current->name, subs, __VA_ARGS__)
> -
> +#define xui(width, name, var, subs, ...) \
> +        xuir(width, name, var, 0, (1 << width) - 1, subs, __VA_ARGS__)
>  
>  #define READ
>  #define READWRITE read
>  #define RWContext GetBitContext
>  
> -#define xui(width, name, var, subs, ...) do { \
> +#define xuir(width, name, var, range_min, range_max, subs, ...) do { \
>          uint32_t value = 0; \
>          CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
>                                     SUBSCRIPTS(subs, __VA_ARGS__), \
> -                                   &value, 0, (1 << width) - 1)); \
> +                                   &value, range_min, range_max)); \
>          var = value; \
>      } while (0)
>  
> @@ -72,7 +75,7 @@
>  #undef READ
>  #undef READWRITE
>  #undef RWContext
> -#undef xui
> +#undef xuir
>  #undef marker_bit
>  #undef nextbits
>  
> @@ -81,10 +84,10 @@
>  #define READWRITE write
>  #define RWContext PutBitContext
>  
> -#define xui(width, name, var, subs, ...) do { \
> +#define xuir(width, name, var, range_min, range_max, subs, ...) do { \
>          CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
>                                      SUBSCRIPTS(subs, __VA_ARGS__), \
> -                                    var, 0, (1 << width) - 1)); \
> +                                    var, range_min, range_max)); \

For consistence's sake with other modules, don't add a xuir define. Make
xui use range_min and range_max (So the above sans the rename), then
make ui pass 0..(1 << width) - 1, and uir pass ranges. Same for the
subscripts variants.

>      } while (0)
>  
>  #define marker_bit() do { \
> @@ -98,7 +101,7 @@
>  #undef READ
>  #undef READWRITE
>  #undef RWContext
> -#undef xui
> +#undef xuir
>  #undef marker_bit
>  #undef nextbits
>  
> diff --git a/libavcodec/cbs_mpeg2_syntax_template.c b/libavcodec/cbs_mpeg2_syntax_template.c
> index 10aaea7734..745a123649 100644
> --- a/libavcodec/cbs_mpeg2_syntax_template.c
> +++ b/libavcodec/cbs_mpeg2_syntax_template.c
> @@ -26,8 +26,8 @@ static int FUNC(sequence_header)(CodedBitstreamContext *ctx, RWContext *rw,
>  
>      ui(8,  sequence_header_code);
>  
> -    ui(12, horizontal_size_value);
> -    ui(12, vertical_size_value);
> +    uir(12, horizontal_size_value, 1, 4095);
> +    uir(12, vertical_size_value,   1, 4095);
>  
>      mpeg2->horizontal_size = current->horizontal_size_value;
>      mpeg2->vertical_size   = current->vertical_size_value;
> @@ -125,9 +125,9 @@ static int FUNC(sequence_display_extension)(CodedBitstreamContext *ctx, RWContex
>  
>      ui(1, colour_description);
>      if (current->colour_description) {
> -        ui(8, colour_primaries);
> -        ui(8, transfer_characteristics);
> -        ui(8, matrix_coefficients);
> +        uir(8, colour_primaries,         1, 255);
> +        uir(8, transfer_characteristics, 1, 255);
> +        uir(8, matrix_coefficients,      1, 255);
>      }
>  
>      ui(14, display_horizontal_size);
>