Re: [PATCH] regulator: vctrl: Fix out of bounds array access for vctrl->vtable

From: Matthias Kaehlcke
Date: Fri Apr 14 2017 - 13:11:52 EST


Hi Axel,

El Fri, Apr 14, 2017 at 10:50:43AM +0800 Axel Lin ha dit:

> Current code only allocates rdesc->n_voltages entries for vctrl->vtable.
> Thus use rdesc->n_voltages instead of n_voltages in the for loop.

This is intended. n_voltages is the number of voltages of the control
regulator. In the first loop of the function we determine how many of
these voltages are usable by the vctrl regulator (=> rdesc->n_voltages).
The loop that populates vctrl->vtable iterates over n_voltages,
however it skips those that are outside of the voltage range for the
control regulator.

> While at it, also switch to use devm_kcalloc instead of devm_kmalloc_array
> + __GFP_ZERO flag and fix the argument order.

This looks good to me.

Thanks

Matthias

> Signed-off-by: Axel Lin <axel.lin@xxxxxxxxxx>
> ---
> drivers/regulator/vctrl-regulator.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/regulator/vctrl-regulator.c b/drivers/regulator/vctrl-regulator.c
> index 6baadef..78de002 100644
> --- a/drivers/regulator/vctrl-regulator.c
> +++ b/drivers/regulator/vctrl-regulator.c
> @@ -345,9 +345,9 @@ static int vctrl_init_vtable(struct platform_device *pdev)
> return -EINVAL;
> }
>
> - vctrl->vtable = devm_kmalloc_array(
> - &pdev->dev, sizeof(struct vctrl_voltage_table),
> - rdesc->n_voltages, GFP_KERNEL | __GFP_ZERO);
> + vctrl->vtable = devm_kcalloc(&pdev->dev, rdesc->n_voltages,
> + sizeof(struct vctrl_voltage_table),
> + GFP_KERNEL);
> if (!vctrl->vtable)
> return -ENOMEM;
>
> @@ -371,7 +371,7 @@ static int vctrl_init_vtable(struct platform_device *pdev)
> NULL);
>
> /* pre-calculate OVP-safe downward transitions */
> - for (i = n_voltages - 1; i > 0; i--) {
> + for (i = rdesc->n_voltages - 1; i > 0; i--) {
> int j;
> int ovp_min_uV = (vctrl->vtable[i].out *
> (100 - vctrl->ovp_threshold)) / 100;