USB: serial/keyspan_pda, fix potential tty NULL dereferences

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

There are several places to check. For easier handling,
tty_port_tty_get is moved directly to the palce where needed in
keyspan_pda_rx_interrupt.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 7 deletions

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 554a8693a463..7b690f3282a2 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -173,7 +173,8 @@ static void keyspan_pda_wakeup_write(struct work_struct *work)
                 container_of(work, struct keyspan_pda_private, wakeup_work);
         struct usb_serial_port *port = priv->port;
         struct tty_struct *tty = tty_port_tty_get(&port->port);
-        tty_wakeup(tty);
+        if (tty)
+                tty_wakeup(tty);
         tty_kref_put(tty);
 }
 
@@ -206,7 +207,7 @@ static void keyspan_pda_request_unthrottle(struct work_struct *work)
 static void keyspan_pda_rx_interrupt(struct urb *urb)
 {
         struct usb_serial_port *port = urb->context;
-        struct tty_struct *tty = tty_port_tty_get(&port->port);
+        struct tty_struct *tty;
         unsigned char *data = urb->transfer_buffer;
         int retval;
         int status = urb->status;
@@ -223,7 +224,7 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
                 /* this urb is terminated, clean up */
                 dbg("%s - urb shutting down with status: %d",
                     __func__, status);
-                goto out;
+                return;
         default:
                 dbg("%s - nonzero urb status received: %d",
                     __func__, status);
@@ -233,12 +234,14 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
         /* see if the message is data or a status interrupt */
         switch (data[0]) {
         case 0:
-                /* rest of message is rx data */
-                if (urb->actual_length) {
+                tty = tty_port_tty_get(&port->port);
+                 /* rest of message is rx data */
+                if (tty && urb->actual_length) {
                         tty_insert_flip_string(tty, data + 1,
                                                 urb->actual_length - 1);
                         tty_flip_buffer_push(tty);
                 }
+                tty_kref_put(tty);
                 break;
         case 1:
                 /* status interrupt */
@@ -265,8 +268,6 @@ exit:
                 dev_err(&port->dev,
                         "%s - usb_submit_urb failed with result %d",
                         __func__, retval);
-out:
-        tty_kref_put(tty);                   
 }