device-dax: Prevent registering drivers without probe callback

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>
Link: https://lore.kernel.org/r/20210205222842.34896-2-uwe@kleine-koenig.org
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 3003558c1a8bba4c984efe135cc1b09634d27201..2b29728ec2fd76ea0e5ea552c855bc34f399b164 100644 (file)
--- 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;