mfd: core: Add locking around 'mfd_of_node_list'

Manipulating a list in the kernel isn't safe without some sort of
mutual exclusion. Add a mutex any time we access / modify
'mfd_of_node_list' to prevent possible crashes.

Cc: stable@vger.kernel.org
Fixes: 466a62d ("mfd: core: Make a best effort attempt to match devices with the correct of_nodes")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patch.msgid.link/20251210113002.1.I6ceaca2cfb7eb25737012b166671f516696be4fd@changeid
Signed-off-by: Lee Jones <lee@kernel.org>

Author: dianders

drivers/mfd/mfd-core.c

@@ -22,6 +22,7 @@
 #include <linux/regulator/consumer.h>
 
 static LIST_HEAD(mfd_of_node_list);
+static DEFINE_MUTEX(mfd_of_node_mutex);
 
 struct mfd_of_node_entry {
 	struct list_head list;
@@ -104,9 +105,11 @@ static int mfd_match_of_node_to_dev(struct platform_device *pdev,
 	u64 of_node_addr;
 
 	/* Skip if OF node has previously been allocated to a device */
-	list_for_each_entry(of_entry, &mfd_of_node_list, list)
-		if (of_entry->np == np)
-			return -EAGAIN;
+	scoped_guard(mutex, &mfd_of_node_mutex) {
+		list_for_each_entry(of_entry, &mfd_of_node_list, list)
+			if (of_entry->np == np)
+				return -EAGAIN;
+	}
 
 	if (!cell->use_of_reg)
 		/* No of_reg defined - allocate first free compatible match */
@@ -128,7 +131,8 @@ static int mfd_match_of_node_to_dev(struct platform_device *pdev,
 
 	of_entry->dev = &pdev->dev;
 	of_entry->np = np;
-	list_add_tail(&of_entry->list, &mfd_of_node_list);
+	scoped_guard(mutex, &mfd_of_node_mutex)
+		list_add_tail(&of_entry->list, &mfd_of_node_list);
 
 	of_node_get(np);
 	device_set_node(&pdev->dev, of_fwnode_handle(np));
@@ -284,11 +288,13 @@ static int mfd_add_device(struct device *parent, int id,
 	if (cell->swnode)
 		device_remove_software_node(&pdev->dev);
 fail_of_entry:
-	list_for_each_entry_safe(of_entry, tmp, &mfd_of_node_list, list)
-		if (of_entry->dev == &pdev->dev) {
-			list_del(&of_entry->list);
-			kfree(of_entry);
-		}
+	scoped_guard(mutex, &mfd_of_node_mutex) {
+		list_for_each_entry_safe(of_entry, tmp, &mfd_of_node_list, list)
+			if (of_entry->dev == &pdev->dev) {
+				list_del(&of_entry->list);
+				kfree(of_entry);
+			}
+	}
 fail_alias:
 	regulator_bulk_unregister_supply_alias(&pdev->dev,
 					       cell->parent_supplies,
@@ -358,11 +364,13 @@ static int mfd_remove_devices_fn(struct device *dev, void *data)
 	if (cell->swnode)
 		device_remove_software_node(&pdev->dev);
 
-	list_for_each_entry_safe(of_entry, tmp, &mfd_of_node_list, list)
-		if (of_entry->dev == &pdev->dev) {
-			list_del(&of_entry->list);
-			kfree(of_entry);
-		}
+	scoped_guard(mutex, &mfd_of_node_mutex) {
+		list_for_each_entry_safe(of_entry, tmp, &mfd_of_node_list, list)
+			if (of_entry->dev == &pdev->dev) {
+				list_del(&of_entry->list);
+				kfree(of_entry);
+			}
+	}
 
 	regulator_bulk_unregister_supply_alias(dev, cell->parent_supplies,
 					       cell->num_parent_supplies);