1 files changed, 16 insertions, 9 deletions

diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index 163386336a5d..08c65c1a3771 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -682,7 +682,6 @@ static void cypress_close(struct usb_serial_port *port, struct file * filp)
 {
         struct cypress_private *priv = usb_get_serial_port_data(port);
         unsigned int c_cflag;
-        unsigned long flags;
         int bps;
         long timeout;
         wait_queue_t wait;
@@ -690,7 +689,7 @@ static void cypress_close(struct usb_serial_port *port, struct file * filp)
         dbg("%s - port %d", __FUNCTION__, port->number);
 
         /* wait for data to drain from buffer */
-        spin_lock_irqsave(&priv->lock, flags);
+        spin_lock_irq(&priv->lock);
         timeout = CYPRESS_CLOSING_WAIT;
         init_waitqueue_entry(&wait, current);
         add_wait_queue(&port->tty->write_wait, &wait);
@@ -698,18 +697,25 @@ static void cypress_close(struct usb_serial_port *port, struct file * filp)
                 set_current_state(TASK_INTERRUPTIBLE);
                 if (cypress_buf_data_avail(priv->buf) == 0
                 || timeout == 0 || signal_pending(current)
-                || !usb_get_intfdata(port->serial->interface))
+                /* without mutex, allowed due to harmless failure mode */
+                || port->serial->disconnected)
                         break;
-                spin_unlock_irqrestore(&priv->lock, flags);
+                spin_unlock_irq(&priv->lock);
                 timeout = schedule_timeout(timeout);
-                spin_lock_irqsave(&priv->lock, flags);
+                spin_lock_irq(&priv->lock);
         }
         set_current_state(TASK_RUNNING);
         remove_wait_queue(&port->tty->write_wait, &wait);
         /* clear out any remaining data in the buffer */
         cypress_buf_clear(priv->buf);
-        spin_unlock_irqrestore(&priv->lock, flags);
-        
+        spin_unlock_irq(&priv->lock);
+
+        /* writing is potentially harmful, lock must be taken */
+        mutex_lock(&port->serial->disc_mutex);
+        if (port->serial->disconnected) {
+                mutex_unlock(&port->serial->disc_mutex);
+                return;
+        }
         /* wait for characters to drain from device */
         bps = tty_get_baud_rate(port->tty);
         if (bps > 1200)
@@ -727,10 +733,10 @@ static void cypress_close(struct usb_serial_port *port, struct file * filp)
                 if (c_cflag & HUPCL) {
                         /* drop dtr and rts */
                         priv = usb_get_serial_port_data(port);
-                        spin_lock_irqsave(&priv->lock, flags);
+                        spin_lock_irq(&priv->lock);
                         priv->line_control = 0;
                         priv->cmd_ctrl = 1;
-                        spin_unlock_irqrestore(&priv->lock, flags);
+                        spin_unlock_irq(&priv->lock);
                         cypress_write(port, NULL, 0);
                 }
         }
@@ -738,6 +744,7 @@ static void cypress_close(struct usb_serial_port *port, struct file * filp)
         if (stats)
                 dev_info (&port->dev, "Statistics: %d Bytes In | %d Bytes Out | %d Commands Issued\n",
                           priv->bytes_in, priv->bytes_out, priv->cmd_count);
+        mutex_unlock(&port->serial->disc_mutex);
 } /* cypress_close */