[PATCH 4.19 111/118] mtd: rawnand: atmel: fix OF child-node lookup

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@xxxxxxxxxx>

commit 5d1e9c2212ea6b4dd735e4fc3dd6279a365d5d10 upstream.

Use the new of_get_compatible_child() helper to lookup the nfc 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 a related nfc-node reference leak.

Fixes: f88fc122cc34 ("mtd: nand: Cleanup/rework the atmel_nand driver")
Cc: stable <stable@xxxxxxxxxxxxxxx>     # 4.11
Cc: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
Cc: Josh Wu <rainyfeeling@xxxxxxxxxxx>
Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mtd/nand/raw/atmel/nand-controller.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/mtd/nand/raw/atmel/nand-controller.c
+++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
@@ -2061,8 +2061,7 @@ atmel_hsmc_nand_controller_legacy_init(s
 	int ret;
 
 	nand_np = dev->of_node;
-	nfc_np = of_find_compatible_node(dev->of_node, NULL,
-					 "atmel,sama5d3-nfc");
+	nfc_np = of_get_compatible_child(dev->of_node, "atmel,sama5d3-nfc");
 	if (!nfc_np) {
 		dev_err(dev, "Could not find device node for sama5d3-nfc\n");
 		return -ENODEV;
@@ -2476,15 +2475,19 @@ static int atmel_nand_controller_probe(s
 	}
 
 	if (caps->legacy_of_bindings) {
+		struct device_node *nfc_node;
 		u32 ale_offs = 21;
 
 		/*
 		 * If we are parsing legacy DT props and the DT contains a
 		 * valid NFC node, forward the request to the sama5 logic.
 		 */
-		if (of_find_compatible_node(pdev->dev.of_node, NULL,
-					    "atmel,sama5d3-nfc"))
+		nfc_node = of_get_compatible_child(pdev->dev.of_node,
+						   "atmel,sama5d3-nfc");
+		if (nfc_node) {
 			caps = &atmel_sama5_nand_caps;
+			of_node_put(nfc_node);
+		}
 
 		/*
 		 * Even if the compatible says we are dealing with an