Re: [PATCH v2 7/9] mfd: mfd-core: Protect against NULL call-back function pointer

From: Daniel Thompson
Date: Mon Oct 21 2019 - 08:30:17 EST


On Mon, Oct 21, 2019 at 11:58:20AM +0100, Lee Jones wrote:
> If a child device calls mfd_cell_{en,dis}able() without an appropriate
> call-back being set, we are likely to encounter a panic. Avoid this
> by adding suitable checking.
>
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>

Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>

> ---
> drivers/mfd/mfd-core.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 8126665bb2d8..90b43b44a15a 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -28,6 +28,11 @@ int mfd_cell_enable(struct platform_device *pdev)
> const struct mfd_cell *cell = mfd_get_cell(pdev);
> int err = 0;
>
> + if (!cell->enable) {
> + dev_dbg(&pdev->dev, "No .enable() call-back registered\n");
> + return 0;
> + }
> +
> /* only call enable hook if the cell wasn't previously enabled */
> if (atomic_inc_return(cell->usage_count) == 1)
> err = cell->enable(pdev);
> @@ -45,6 +50,11 @@ int mfd_cell_disable(struct platform_device *pdev)
> const struct mfd_cell *cell = mfd_get_cell(pdev);
> int err = 0;
>
> + if (!cell->enable) {
> + dev_dbg(&pdev->dev, "No .disable() call-back registered\n");
> + return 0;
> + }
> +
> /* only disable if no other clients are using it */
> if (atomic_dec_return(cell->usage_count) == 0)
> err = cell->disable(pdev);
> --
> 2.17.1
>