mmc: meson-mx-sdio: fix OF child-node lookup

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

1 files 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)