RE: [PATCH] usb/core: fix NULL pointer dereference inrecursively_mark_NOTATTACHED

[Alan Stern]

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--;


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/