[PATCH] driver-core: fix race between device_register and driver_register

[Sebastian Ott <sebott@linux.vnet.ibm.com>]

When a device is registered to a bus it will be a) added to the list
of devices of the bus and b) bind to a driver (if one matches). As a
result of a driver being registered at this bus between a) and b) this
device could already be bound to a driver. This leads to a warning
and incorrect refcounting.
To fix this add a check to device_attach to identify an already bound
device.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
---
 drivers/base/dd.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -245,6 +245,10 @@ int device_attach(struct device *dev)
 
 	device_lock(dev);
 	if (dev->driver) {
+		if (klist_node_attached(&dev->p->knode_driver)) {
+			ret = 1;
+			goto out_unlock;
+		}
 		ret = device_bind_driver(dev);
 		if (ret == 0)
 			ret = 1;
@@ -257,6 +261,7 @@ int device_attach(struct device *dev)
 		ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
 		pm_runtime_put_sync(dev);
 	}
+out_unlock:
 	device_unlock(dev);
 	return ret;
 }