[PATCH 3.16 031/148] usb: gadget: u_serial: add missing port entry locking

[Ben Hutchings]

3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

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

From: MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>

commit daf82bd24e308c5a83758047aff1bd81edda4f11 upstream.

gserial_alloc_line() misses locking (for a release barrier) while
resetting port entry on TTY allocation failure. Fix this.

Signed-off-by: MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Tested-by: Ladislav Michl <ladis@xxxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/gadget/u_serial.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -1140,8 +1140,10 @@ int gserial_alloc_line(unsigned char *li
 				__func__, port_num, PTR_ERR(tty_dev));
 
 		ret = PTR_ERR(tty_dev);
+		mutex_lock(&ports[port_num].lock);
 		port = ports[port_num].port;
 		ports[port_num].port = NULL;
+		mutex_unlock(&ports[port_num].lock);
 		gserial_free_port(port);
 		goto err;
 	}