net/smc: remove device from smcd_dev_list after failed device_add()

If the device_add() for a smcd_dev fails, there's no cleanup step that
rolls back the earlier list_add(). The device subsequently gets freed,
and we end up with a corrupted list.

Add some error handling that removes the device from the list.

Fixes: c6ba7c9b ("net/smc: add base infrastructure for SMC-D and ISM")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_ism.c

@@ -428,6 +428,8 @@ EXPORT_SYMBOL_GPL(smcd_alloc_dev);
 
 int smcd_register_dev(struct smcd_dev *smcd)
 {
+	int rc;
+
 	mutex_lock(&smcd_dev_list.mutex);
 	if (list_empty(&smcd_dev_list.list)) {
 		u8 *system_eid = NULL;
@@ -447,7 +449,14 @@ int smcd_register_dev(struct smcd_dev *smcd)
 			    dev_name(&smcd->dev), smcd->pnetid,
 			    smcd->pnetid_by_user ? " (user defined)" : "");
 
-	return device_add(&smcd->dev);
+	rc = device_add(&smcd->dev);
+	if (rc) {
+		mutex_lock(&smcd_dev_list.mutex);
+		list_del(&smcd->list);
+		mutex_unlock(&smcd_dev_list.mutex);
+	}
+
+	return rc;
 }
 EXPORT_SYMBOL_GPL(smcd_register_dev);