Re: [PATCH v2 4/9] mmc: meson-mx-sdio: fix OF child-node lookup

[Ulf Hansson <ulf.hansson@linaro.org>]

On 27 August 2018 at 10:21, Johan Hovold <johan@kernel.org> wrote:
> Use the new of_get_compatible_child() helper to lookup the slot child
> node instead of using of_find_compatible_node(), which searches the
> entire tree from a given start node and thus can return an unrelated
> (i.e. non-child) node.
>
> This also addresses a potential use-after-free (e.g. after probe
> deferral) as the tree-wide helper drops a reference to its first
> argument (i.e. the node of the device being probed).
>
> While at it, also fix up the related slot-node reference leak.
>
> Fixes: ed80a13bb4c4 ("mmc: meson-mx-sdio: Add a driver for the Amlogic Meson8 and Meson8b SoCs")
> Cc: stable <stable@vger.kernel.org>     # 4.15
> Cc: Carlo Caione <carlo@endlessm.com>
> Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Signed-off-by: Johan Hovold <johan@kernel.org>

Acked-by: Ulf Hansson <ulf.hansson@linaro.org>

Kind regards
Uffe

> ---
>  drivers/mmc/host/meson-mx-sdio.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-mx-sdio.c b/drivers/mmc/host/meson-mx-sdio.c
> index 09cb89645d06..2cfec33178c1 100644
> --- a/drivers/mmc/host/meson-mx-sdio.c
> +++ b/drivers/mmc/host/meson-mx-sdio.c
> @@ -517,19 +517,23 @@ static struct mmc_host_ops meson_mx_mmc_ops = {
>  static struct platform_device *meson_mx_mmc_slot_pdev(struct device *parent)
>  {
>         struct device_node *slot_node;
> +       struct platform_device *pdev;
>
>         /*
>          * TODO: the MMC core framework currently does not support
>          * controllers with multiple slots properly. So we only register
>          * the first slot for now
>          */
> -       slot_node = of_find_compatible_node(parent->of_node, NULL, "mmc-slot");
> +       slot_node = of_get_compatible_child(parent->of_node, "mmc-slot");
>         if (!slot_node) {
>                 dev_warn(parent, "no 'mmc-slot' sub-node found\n");
>                 return ERR_PTR(-ENOENT);
>         }
>
> -       return of_platform_device_create(slot_node, NULL, parent);
> +       pdev = of_platform_device_create(slot_node, NULL, parent);
> +       of_node_put(slot_node);
> +
> +       return pdev;
>  }
>
>  static int meson_mx_mmc_add_host(struct meson_mx_mmc_host *host)
> --
> 2.18.0
>