[FFmpeg-devel] [PATCH] vorbisdec: Simplify, do no calculate same value twice.

[Reimar Döffinger]

On Wed, Apr 11, 2012 at 09:45:32PM +0200, Reimar Döffinger wrote:
> The 0 assignment is just for paranoia reasons, the function
> is only called from init and we should bail out directly
> on failure.
> 
> Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
> ---
>  libavcodec/vorbisdec.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c
> index ddc79fc..2268a45 100644
> --- a/libavcodec/vorbisdec.c
> +++ b/libavcodec/vorbisdec.c
> @@ -685,10 +685,13 @@ static int vorbis_parse_setup_hdr_residues(vorbis_context *vc)
>          res_setup->begin          = get_bits(gb, 24);
>          res_setup->end            = get_bits(gb, 24);
>          res_setup->partition_size = get_bits(gb, 24) + 1;
> +        res_setup->ptns_to_read =
> +            (res_setup->end - res_setup->begin) / res_setup->partition_size;
>          /* Validations to prevent a buffer overflow later. */
>          if (res_setup->begin>res_setup->end ||
>              res_setup->end > (res_setup->type == 2 ? vc->audio_channels : 1) * vc->blocksize[1] / 2 ||
> -            (res_setup->end-res_setup->begin) / res_setup->partition_size > V_MAX_PARTITIONS) {
> +            res_setup->ptns_to_read > V_MAX_PARTITIONS) {
> +            res_setup->ptns_to_read = 0;

Ouch, something is broken here.
ptns_to_read is only uint16_t, but V_MAX_PARTITIONS is (1<<20).
It seems likely to me that ptns_to_read should be unsigned instead, but
maybe someone else could look into that?