[100/107] USB: fix regression occurring during device removal

[Greg KH]

2.6.39-stable review patch.  If anyone has any objections, please let us know.

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

From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

commit e534c5b831c8b8e9f5edee5c8a37753c808b80dc upstream.

This patch (as1476) fixes a regression introduced by
fccf4e86200b8f5edd9a65da26f150e32ba79808 (USB: Free bandwidth when
usb_disable_device is called).  usb_disconnect() grabs the
bandwidth_mutex before calling usb_disable_device(), which calls down
indirectly to usb_set_interface(), which tries to acquire the
bandwidth_mutex.

The fix causes usb_set_interface() to return early when it is called
for an interface that has already been unregistered, which is what
happens in usb_disable_device().

Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Tested-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/usb/core/message.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1286,6 +1286,8 @@ int usb_set_interface(struct usb_device
 			interface);
 		return -EINVAL;
 	}
+	if (iface->unregistering)
+		return -ENODEV;
 
 	alt = usb_altnum_to_altsetting(iface, alternate);
 	if (!alt) {


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