[34-longterm 181/247] USB: serial/kobil_sct, fix potential tty NULL dereference

[Paul Gortmaker]

From: Jiri Slaby <jslaby@xxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 6960f40a954619857e7095a6179eef896f297077 upstream.

Make sure that we check the return value of tty_port_tty_get.
Sometimes it may return NULL and we later dereference that.

The only place here is in kobil_read_int_callback, so fix it.

Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 drivers/usb/serial/kobil_sct.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/serial/kobil_sct.c b/drivers/usb/serial/kobil_sct.c
index bd5bd85..b382d9a 100644
--- a/drivers/usb/serial/kobil_sct.c
+++ b/drivers/usb/serial/kobil_sct.c
@@ -372,7 +372,7 @@ static void kobil_read_int_callback(struct urb *urb)
 	}
 
 	tty = tty_port_tty_get(&port->port);
-	if (urb->actual_length) {
+	if (tty && urb->actual_length) {
 
 		/* BEGIN DEBUG */
 		/*
-- 
1.7.4.4

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