linux-kernel - [PATCH 3.16 133/357] usb: hub: take hub->hdev reference when processing from eventlist

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Date:	Fri,  3 Oct 2014 14:28:39 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Joe Lawrence <joe.lawrence@...atus.com>,
	Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH 3.16 133/357] usb: hub: take hub->hdev reference when processing from eventlist

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joe Lawrence <joe.lawrence@...atus.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@...atus.com>
Suggested-by: David Bulkow <david.bulkow@...atus.com> for using kref
Suggested-by: Alan Stern <stern@...land.harvard.edu> for placement
Acked-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/core/hub.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -5008,9 +5008,10 @@ static void hub_events(void)
 
 		hub = list_entry(tmp, struct usb_hub, event_list);
 		kref_get(&hub->kref);
+		hdev = hub->hdev;
+		usb_get_dev(hdev);
 		spin_unlock_irq(&hub_event_lock);
 
-		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",
@@ -5123,6 +5124,7 @@ static void hub_events(void)
 		usb_autopm_put_interface(intf);
  loop_disconnected:
 		usb_unlock_device(hdev);
+		usb_put_dev(hdev);
 		kref_put(&hub->kref, hub_release);
 
 	} /* end while (1) */


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