From 15e5bee33ffc11d0e5c6f819a65e7881c5c407be Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold@gmail.com>
Date: Tue, 22 Mar 2011 11:12:10 +0100
Subject: [PATCH] USB: cdc-acm: fix potential null-pointer dereference

Must check return value of tty_port_tty_get.

Cc: stable <stable@kernel.org>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 drivers/usb/class/cdc-acm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 00d809dfe84d..175637148962 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -533,6 +533,8 @@ static void acm_softint(struct work_struct *work)
 	if (!ACM_READY(acm))
 		return;
 	tty = tty_port_tty_get(&acm->port);
+	if (!tty)
+		return;
 	tty_wakeup(tty);
 	tty_kref_put(tty);
 }