[PATCH 3.13 049/163] usb: hub: take hub->hdev reference when processing from eventlist

Kamal Mostafa kamal at canonical.com
Thu Oct 9 21:01:14 UTC 2014 -stable review patch.  If anyone has any objections, please let me know.


From: Joe Lawrence <joe.lawrence at stratus.com>

commit c605f3cdff53a743f6d875b76956b239deca1272 upstream.

During surprise device hotplug removal tests, it was observed that
hub_events may try to call usb_lock_device on a device that has already
been freed. Protect the usb_device by taking out a reference (under the
hub_event_lock) when hub_events pulls it off the list, returning the
reference after hub_events is finished using it.

Signed-off-by: Joe Lawrence <joe.lawrence at stratus.com>
Suggested-by: David Bulkow <david.bulkow at stratus.com> for using kref
Suggested-by: Alan Stern <stern at rowland.harvard.edu> for placement
Acked-by: Alan Stern <stern at rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 drivers/usb/core/hub.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index a80e195..9f179ea 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4729,9 +4729,10 @@ static void hub_events(void)
 		hub = list_entry(tmp, struct usb_hub, event_list);
+		hdev = hub->hdev;
+		usb_get_dev(hdev);
-		hdev = hub->hdev;
 		hub_dev = hub->intfdev;
 		intf = to_usb_interface(hub_dev);
 		dev_dbg(hub_dev, "state %d ports %d chg %04x evt %04x\n",
@@ -4944,6 +4945,7 @@ static void hub_events(void)
+		usb_put_dev(hdev);
 		kref_put(&hub->kref, hub_release);
 	} /* end while (1) */

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