[FFmpeg-devel] [PATCH 02/10] avformat/matroskadec: Don't zero unnecessarily

[James Almer]

On 3/8/2019 6:25 AM, Andreas Rheinhardt wrote:
> It is only necessary to zero the initial allocated memory used to store
> the size of laced frames if the block used Xiph lacing. Otherwise no
> unintialized data was ever used, so use av_malloc instead of av_mallocz.
> 
> Also use the correct type for the allocations.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at googlemail.com>
> ---
>  libavformat/matroskadec.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> index de27d63b17..8a14764d1a 100644
> --- a/libavformat/matroskadec.c
> +++ b/libavformat/matroskadec.c
> @@ -2796,7 +2796,7 @@ static int matroska_parse_laces(MatroskaDemuxContext *matroska, uint8_t **buf,
>  
>      if (!type) {
>          *laces    = 1;
> -        *lace_buf = av_mallocz(sizeof(int));
> +        *lace_buf = av_malloc(sizeof(**lace_buf));
>          if (!*lace_buf)
>              return AVERROR(ENOMEM);
>  
> @@ -2808,7 +2808,7 @@ static int matroska_parse_laces(MatroskaDemuxContext *matroska, uint8_t **buf,
>      *laces    = *data + 1;
>      data     += 1;
>      size     -= 1;
> -    lace_size = av_mallocz(*laces * sizeof(int));
> +    lace_size = av_malloc(*laces * sizeof(*lace_size));
>      if (!lace_size)
>          return AVERROR(ENOMEM);
>  
> @@ -2818,6 +2818,8 @@ static int matroska_parse_laces(MatroskaDemuxContext *matroska, uint8_t **buf,
>          uint8_t temp;
>          uint32_t total = 0;
>          for (n = 0; res == 0 && n < *laces - 1; n++) {
> +            lace_size[n] = 0;
> +
>              while (1) {
>                  if (size <= total) {
>                      res = AVERROR_INVALIDDATA;
> 

Should be ok if tested under Valgrind to make sure there's really no
uninitialized data read.