On Tue, 24 Dec 2013, Alan Stern wrote:
> > This is my analysis, how do you think?
>
> There is another reason why usb_hub_to_struct_hub() could return NULL:
> if usb_get_intfdata(hdev->actconfig->interface[0]) is NULL. This could
> happen if recursively_mark_NOTATTACHED() is called _while_
> hub_disconnect() is running.
>
> There should be locking to prevent this, but there isn't. That's what
> we need to fix. It's not an easy problem. Can you figure out a
> correct solution?
I think this will fix it. Take a close look and do some careful
testing.
Alan Stern
Index: usb-3.13/drivers/usb/core/hub.c
===================================================================
--- usb-3.13.orig/drivers/usb/core/hub.c
+++ usb-3.13/drivers/usb/core/hub.c
@@ -1622,11 +1622,14 @@ static void hub_disconnect(struct usb_in
hub->error = 0;
hub_quiesce(hub, HUB_DISCONNECT);
- usb_set_intfdata (intf, NULL);
-
for (i = 0; i < hdev->maxchild; i++)
usb_hub_remove_port_device(hub, i + 1);
+
+ /* Avoid races with recursively_mark_NOTATTACHED() */
+ spin_lock_irq(&device_state_lock);
hub->hdev->maxchild = 0;
+ usb_set_intfdata(intf, NULL);
+ spin_unlock_irq(&device_state_lock);
if (hub->hdev->speed == USB_SPEED_HIGH)
highspeed_hubs--;
--
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