driver core: fix race between creating/querying glue dir and its cleanup

The global mutex of 'gdp_mutex' is used to serialize creating/querying
glue dir and its cleanup. Turns out it isn't a perfect way because
part(kobj_kset_leave()) of the actual cleanup action() is done inside
the release handler of the glue dir kobject. That means gdp_mutex has
to be held before releasing the last reference count of the glue dir
kobject.

This patch moves glue dir's cleanup after kobject_del() in device_del()
for avoiding the race.

Cc: Yijing Wang <wangyijing@huawei.com>
Reported-by: Chandra Sekhar Lingutla <clingutla@codeaurora.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 29 insertions, 10 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 0a8bdade53f2..88df65d1e6f6 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -836,11 +836,29 @@ static struct kobject *get_device_parent(struct device *dev,
         return NULL;
 }
 
+static inline bool live_in_glue_dir(struct kobject *kobj,
+                                    struct device *dev)
+{
+        if (!kobj || !dev->class ||
+            kobj->kset != &dev->class->p->glue_dirs)
+                return false;
+        return true;
+}
+
+static inline struct kobject *get_glue_dir(struct device *dev)
+{
+        return dev->kobj.parent;
+}
+
+/*
+ * make sure cleaning up dir as the last step, we need to make
+ * sure .release handler of kobject is run with holding the
+ * global lock
+ */
 static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
 {
         /* see if we live in a "glue" directory */
-        if (!glue_dir || !dev->class ||
-            glue_dir->kset != &dev->class->p->glue_dirs)
+        if (!live_in_glue_dir(glue_dir, dev))
                 return;
 
         mutex_lock(&gdp_mutex);
@@ -848,11 +866,6 @@ static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
         mutex_unlock(&gdp_mutex);
 }
 
-static void cleanup_device_parent(struct device *dev)
-{
-        cleanup_glue_dir(dev, dev->kobj.parent);
-}
-
 static int device_add_class_symlinks(struct device *dev)
 {
         struct device_node *of_node = dev_of_node(dev);
@@ -1028,6 +1041,7 @@ int device_add(struct device *dev)
         struct kobject *kobj;
         struct class_interface *class_intf;
         int error = -EINVAL;
+        struct kobject *glue_dir = NULL;
 
         dev = get_device(dev);
         if (!dev)
@@ -1072,8 +1086,10 @@ int device_add(struct device *dev)
         /* first, register with generic layer. */
         /* we require the name to be set before, and pass NULL */
         error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
-        if (error)
+        if (error) {
+                glue_dir = get_glue_dir(dev);
                 goto Error;
+        }
 
         /* notify platform of device entry */
         if (platform_notify)
@@ -1154,9 +1170,10 @@ done:
         device_remove_file(dev, &dev_attr_uevent);
  attrError:
         kobject_uevent(&dev->kobj, KOBJ_REMOVE);
+        glue_dir = get_glue_dir(dev);
         kobject_del(&dev->kobj);
  Error:
-        cleanup_device_parent(dev);
+        cleanup_glue_dir(dev, glue_dir);
         put_device(parent);
 name_error:
         kfree(dev->p);
@@ -1232,6 +1249,7 @@ EXPORT_SYMBOL_GPL(put_device);
 void device_del(struct device *dev)
 {
         struct device *parent = dev->parent;
+        struct kobject *glue_dir = NULL;
         struct class_interface *class_intf;
 
         /* Notify clients of device removal.  This call must come
@@ -1276,8 +1294,9 @@ void device_del(struct device *dev)
                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                              BUS_NOTIFY_REMOVED_DEVICE, dev);
         kobject_uevent(&dev->kobj, KOBJ_REMOVE);
-        cleanup_device_parent(dev);
+        glue_dir = get_glue_dir(dev);
         kobject_del(&dev->kobj);
+        cleanup_glue_dir(dev, glue_dir);
         put_device(parent);
 }
 EXPORT_SYMBOL_GPL(device_del);