[40/55] USB: cdc-acm: fix potential null-pointer dereference

[Greg KH]

2.6.37-stable review patch.  If anyone has any objections, please let us know.

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

From: Johan Hovold <jhovold@xxxxxxxxx>

commit 15e5bee33ffc11d0e5c6f819a65e7881c5c407be upstream.

Must check return value of tty_port_tty_get.

Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/usb/class/cdc-acm.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -533,6 +533,8 @@ static void acm_softint(struct work_stru
 	if (!ACM_READY(acm))
 		return;
 	tty = tty_port_tty_get(&acm->port);
+	if (!tty)
+		return;
 	tty_wakeup(tty);
 	tty_kref_put(tty);
 }


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