[PATCH v2 1/5] dax-device: Prevent registering drivers without probe callback

["Uwe Kleine-König" <uwe@kleine-koenig.org>]

The bus probe function dax_bus_probe() calls the probe callback without
checking it to be non-NULL. Prevent a NULL pointer exception if a driver
without a probe function is registered by refusing to register this
driver.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
 drivers/dax/bus.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 737b207c9e30..72fc4b9b9ae6 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -1392,6 +1392,13 @@ int __dax_driver_register(struct dax_device_driver *dax_drv,
 	struct device_driver *drv = &dax_drv->drv;
 	int rc = 0;
 
+	/*
+	 * dax_bus_probe() calls dax_drv->probe() unconditionally.
+	 * So better be safe than sorry and ensure it is provided.
+	 */
+	if (!dax_drv->probe)
+		return -EINVAL;
+
 	INIT_LIST_HEAD(&dax_drv->ids);
 	drv->owner = module;
 	drv->name = mod_name;
-- 
2.29.2