[ 058/117] tty: Allow uart_register/unregister/register

3.2-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>
Signed-off-by: Ben Hutchings <redacted>
---
 drivers/tty/serial/serial_core.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 59fb3ba..a21dc8e 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c

@@ -2282,6 +2282,7 @@ void uart_unregister_driver(struct uart_driver *drv)
 	tty_unregister_driver(p);
 	put_tty_driver(p);
 	kfree(drv->state);
+	drv->state = NULL;
 	drv->tty_driver = NULL;
 }