[PATCH 1/2] fixes for adt7410

[Hartmut Knaack <knaack.h@gmx.de>]

This patch adds some checks prior to accessing device attribute lists in industrialio-event.c.

Signed-off-by: Harmut Knaack <knaack.h@gmx.de>
---
diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
index b49059d..fe68e90 100644
--- a/drivers/iio/industrialio-event.c
+++ b/drivers/iio/industrialio-event.c
@@ -425,11 +425,13 @@ int iio_device_register_eventset(struct iio_dev *indio_dev)
                *attrcount_orig);
     attrn = attrcount_orig;
     /* Add all elements from the list. */
-    list_for_each_entry(p,
-                &indio_dev->event_interface->dev_attr_list,
-                l)
-        indio_dev->event_interface->group.attrs[attrn++] =
-            &p->dev_attr.attr;
+    if (indio_dev->event_interface->dev_attr_list.next)
+        list_for_each_entry(p,
+                &indio_dev->event_interface->dev_attr_list,
+                l)
+            indio_dev->event_interface->group.attrs[attrn++] =
+                &p->dev_attr.attr;
+
     indio_dev->groups[indio_dev->groupcounter++] =
         &indio_dev->event_interface->group;
 
@@ -447,7 +449,9 @@ void iio_device_unregister_eventset(struct iio_dev *indio_dev)
 {
     if (indio_dev->event_interface == NULL)
         return;
-    __iio_remove_event_config_attrs(indio_dev);
-    kfree(indio_dev->event_interface->group.attrs);
+    if (indio_dev->event_interface->dev_attr_list.next)
+        __iio_remove_event_config_attrs(indio_dev);
+    if (indio_dev->event_interface->group.attrs)
+        kfree(indio_dev->event_interface->group.attrs);
     kfree(indio_dev->event_interface);
 }