[PATCH] USB: omninet: fix potential tty NULL dereference

[Alexey Khoroshilov]

Add check for return value of tty_port_tty_get,
since it can return NULL after port hangup that may happen anytime.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
---
 drivers/usb/serial/omninet.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/serial/omninet.c b/drivers/usb/serial/omninet.c
index 6f3d705..493c892 100644
--- a/drivers/usb/serial/omninet.c
+++ b/drivers/usb/serial/omninet.c
@@ -185,10 +185,12 @@ static void omninet_read_bulk_callback(struct urb *urb)
 
 	if (urb->actual_length && header->oh_len) {
 		struct tty_struct *tty = tty_port_tty_get(&port->port);
-		tty_insert_flip_string(tty, data + OMNINET_DATAOFFSET,
+		if (tty) {
+			tty_insert_flip_string(tty, data + OMNINET_DATAOFFSET,
 							header->oh_len);
-		tty_flip_buffer_push(tty);
-		tty_kref_put(tty);
+			tty_flip_buffer_push(tty);
+			tty_kref_put(tty);
+		}
 	}
 
 	/* Continue trying to always read  */
-- 
1.7.9.5

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