[PATCH] driver core: fix shutdown races with probe/remove(v1)

[Ming Lei <ming.lei@canonical.com>]

Firstly, .shutdown callback may touch a uninitialized hardware
if dev->driver is set and .probe is not completed.

Secondly, device_shutdown() may dereference a null pointer to cause
oops when dev->driver is cleared after it is checked in
device_shutdown().

So just hold device lock and its parent lock if it has to fix the
races.

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 drivers/base/core.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 346be8b..cbc8bd2 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1820,6 +1820,11 @@ void device_shutdown(void)
 		list_del_init(&dev->kobj.entry);
 		spin_unlock(&devices_kset->list_lock);
 
+		/*hold lock[s] to avoid races with .probe/.release*/
+		if (dev->parent)
+			device_lock(dev->parent);
+		device_lock(dev);
+
 		/* Don't allow any more runtime suspends */
 		pm_runtime_get_noresume(dev);
 		pm_runtime_barrier(dev);
@@ -1831,6 +1836,9 @@ void device_shutdown(void)
 			dev_dbg(dev, "shutdown\n");
 			dev->driver->shutdown(dev);
 		}
+		device_unlock(dev);
+		if (dev->parent)
+			device_unlock(dev->parent);
 		put_device(dev);
 
 		spin_lock(&devices_kset->list_lock);
-- 
1.7.9.5