[PATCH 7/9] USB: serial: fix missing locking on fifo in write callback

[Johan Hovold <jhovold@gmail.com>]

On errors the fifo was reset without any locking. This could race with
write which do kfifo_put and perhaps also chars_in_buffer and write_room.

Every other access to the fifo is protected using the port lock so
better add it to the error path as well.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
---
 drivers/usb/serial/generic.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 8d6d790..d3ef69f 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -518,10 +518,13 @@ void usb_serial_generic_write_bulk_callback(struct urb *urb)
 		port->write_urb_busy = 0;
 		spin_unlock_irqrestore(&port->lock, flags);
 
-		if (status)
+		if (status) {
+			spin_lock_irqsave(&port->lock, flags);
 			kfifo_reset_out(&port->write_fifo);
-		else
+			spin_unlock_irqrestore(&port->lock, flags);
+		} else {
 			usb_serial_generic_write_start(port);
+		}
 	}
 
 	if (status)
-- 
1.7.0.2