usb: cdc-acm: move ldisc dcd notification outside of acm's read lock

dcd_change notification call moved outside of the acm->read_lock
to protect any future tty ldisc that calls wait_serial_change()

Signed-off-by: Dan Drown <dan-netdev@drown.org>
Acked-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/ZN1zV/zjPgpGlHXo@vps3.drown.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 9b34199..dfb28c7 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -319,23 +319,24 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
                }
 
                difference = acm->ctrlin ^ newctrl;
+
+               if ((difference & USB_CDC_SERIAL_STATE_DCD) && acm->port.tty) {
+                       struct tty_ldisc *ld = tty_ldisc_ref(acm->port.tty);
+                       if (ld) {
+                               if (ld->ops->dcd_change)
+                                       ld->ops->dcd_change(acm->port.tty, newctrl & USB_CDC_SERIAL_STATE_DCD);
+                               tty_ldisc_deref(ld);
+                       }
+               }
+
                spin_lock_irqsave(&acm->read_lock, flags);
                acm->ctrlin = newctrl;
                acm->oldcount = acm->iocount;
 
                if (difference & USB_CDC_SERIAL_STATE_DSR)
                        acm->iocount.dsr++;
-               if (difference & USB_CDC_SERIAL_STATE_DCD) {
-                       if (acm->port.tty) {
-                               struct tty_ldisc *ld = tty_ldisc_ref(acm->port.tty);
-                               if (ld) {
-                                       if (ld->ops->dcd_change)
-                                               ld->ops->dcd_change(acm->port.tty, newctrl & USB_CDC_SERIAL_STATE_DCD);
-                                       tty_ldisc_deref(ld);
-                               }
-                       }
+               if (difference & USB_CDC_SERIAL_STATE_DCD)
                        acm->iocount.dcd++;
-               }
                if (newctrl & USB_CDC_SERIAL_STATE_BREAK) {
                        acm->iocount.brk++;
                        tty_insert_flip_char(&acm->port, 0, TTY_BREAK);