On Thu, 30 Jun 2016 16:04:44 +0200,
Takashi Sakamoto wrote:
>
> The 'dimen' field in struct snd_ctl_elem_info is used to compose all of
> members in the element as multi-dimensional matrix. The field has four
> members. Each member represents the width in each dimension level by
> element member unit. For example, if the members consist of typical
> two dimensional matrix, the dimen[0] represents the number of rows
> and dimen[1] represents the number of columns (or vise-versa).
>
> The total members in the matrix should be within the number of members in
> the element, while current implementation has no validator of this
> information. In a view of userspace applications, the information must be
> valid so that it cannot cause any bugs such as buffer-over-run.
>
> This commit adds a validator of dimension information for userspace
> applications which add new element sets. When they add the element sets
> with wrong dimension information, they receive -EINVAL.
>
> Signed-off-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>
> ---
> sound/core/control.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/sound/core/control.c b/sound/core/control.c
> index a85d455..af167ff 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -805,6 +805,33 @@ static int snd_ctl_elem_list(struct snd_card *card,
> return 0;
> }
>
> +static bool validate_dimension(struct snd_ctl_elem_info *info)
> +{
> + unsigned int elements;
> + unsigned int i;
> +
> + /*
> + * When drivers don't use dimen field, this value is zero and pass the
> + * validation. Else, calculated number of elements is validated.
> + */
> + elements = info->dimen.d[0];
> + for (i = 1; i < ARRAY_SIZE(info->dimen.d); ++i) {
> + if (info->dimen.d[i] == 0)
> + break;
> + if (info->dimen.d[i] < 0)
> + return false;
> + elements *= info->dimen.d[i];
> + }
Just minor nit-picks:
- No check for the negative sign of the first element?
- It'd be clearer to check zero of the first element before the
loop.
- Safer to have an integer overflow check in such calculation.
thanks,
Takashi
> + /* The rest of level should be zero. */
> + for (++i; i < ARRAY_SIZE(info->dimen.d); ++i) {
> + if (info->dimen.d[i] != 0)
> + return false;
> + }
> +
> + return elements <= info->count;
> +}
> +
> static int snd_ctl_elem_info(struct snd_ctl_file *ctl,
> struct snd_ctl_elem_info *info)
> {
> @@ -1272,6 +1299,8 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
> if (info->count < 1 ||
> info->count > max_value_counts[info->type])
> return -EINVAL;
> + if (!validate_dimension(info))
> + return -EINVAL;
> private_size = value_sizes[info->type] * info->count;
>
> /*
> --
> 2.7.4
>
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
