driver core: fix shutdown races with probe/remove(v3)

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 has been 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>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 846d12b5d579..65849a9aeece 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1812,6 +1812,13 @@ void device_shutdown(void)
         while (!list_empty(&devices_kset->list)) {
                 dev = list_entry(devices_kset->list.prev, struct device,
                                 kobj.entry);
+
+                /*
+                 * hold reference count of device's parent to
+                 * prevent it from being freed because parent's
+                 * lock is to be held
+                 */
+                get_device(dev->parent);
                 get_device(dev);
                 /*
                  * Make sure the device is off the kset list, in the
@@ -1820,6 +1827,11 @@ void device_shutdown(void)
                 list_del_init(&dev->kobj.entry);
                 spin_unlock(&devices_kset->list_lock);
 
+                /* hold lock to avoid race 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);
@@ -1831,7 +1843,13 @@ 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);
+                put_device(dev->parent);
 
                 spin_lock(&devices_kset->list_lock);
         }