driver core: platform: use generic driver_override infrastructure

When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]

Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: 3d713e0e382e ("driver core: platform: add device binding path 'driver_override'")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/20260303115720.48783-5-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 5 insertions, 32 deletions

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index b45d41b018ca..d44591d52e36 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -603,7 +603,6 @@ static void platform_device_release(struct device *dev)
 	kfree(pa->pdev.dev.platform_data);
 	kfree(pa->pdev.mfd_cell);
 	kfree(pa->pdev.resource);
-	kfree(pa->pdev.driver_override);
 	kfree(pa);
 }
 
@@ -1306,38 +1305,9 @@ static ssize_t numa_node_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(numa_node);
 
-static ssize_t driver_override_show(struct device *dev,
-				    struct device_attribute *attr, char *buf)
-{
-	struct platform_device *pdev = to_platform_device(dev);
-	ssize_t len;
-
-	device_lock(dev);
-	len = sysfs_emit(buf, "%s\n", pdev->driver_override);
-	device_unlock(dev);
-
-	return len;
-}
-
-static ssize_t driver_override_store(struct device *dev,
-				     struct device_attribute *attr,
-				     const char *buf, size_t count)
-{
-	struct platform_device *pdev = to_platform_device(dev);
-	int ret;
-
-	ret = driver_set_override(dev, &pdev->driver_override, buf, count);
-	if (ret)
-		return ret;
-
-	return count;
-}
-static DEVICE_ATTR_RW(driver_override);
-
 static struct attribute *platform_dev_attrs[] = {
 	&dev_attr_modalias.attr,
 	&dev_attr_numa_node.attr,
-	&dev_attr_driver_override.attr,
 	NULL,
 };
 
@@ -1377,10 +1347,12 @@ static int platform_match(struct device *dev, const struct device_driver *drv)
 {
 	struct platform_device *pdev = to_platform_device(dev);
 	struct platform_driver *pdrv = to_platform_driver(drv);
+	int ret;
 
 	/* When driver_override is set, only bind to the matching driver */
-	if (pdev->driver_override)
-		return !strcmp(pdev->driver_override, drv->name);
+	ret = device_match_driver_override(dev, drv);
+	if (ret >= 0)
+		return ret;
 
 	/* Attempt an OF style match first */
 	if (of_driver_match_device(dev, drv))
@@ -1516,6 +1488,7 @@ static const struct dev_pm_ops platform_dev_pm_ops = {
 const struct bus_type platform_bus_type = {
 	.name		= "platform",
 	.dev_groups	= platform_dev_groups,
+	.driver_override = true,
 	.match		= platform_match,
 	.uevent		= platform_uevent,
 	.probe		= platform_probe,