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

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

From: Alan Cox <redacted>

commit 1e66cded334e6cea596c72f6f650eec351b1e959 upstream.

This is legitimate but because we don't clear the drv->state pointer in the
unregister code causes a bogus BUG().

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=42880
Signed-off-by: Alan Cox <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/serial_core.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c

@@ -2325,6 +2325,7 @@ void uart_unregister_driver(struct uart_
 	tty_unregister_driver(p);
 	put_tty_driver(p);
 	kfree(drv->state);
+	drv->state = NULL;
 	drv->tty_driver = NULL;
 }