[PATCH AUTOSEL 6.4 24/25] usb: cdc-acm: move ldisc dcd notification outside of acm's read lock

[Sasha Levin <sashal@kernel.org>]

From: Dan Drown <dan-netdev@drown.org>

[ Upstream commit f72ae60881ff685004d7de7152517607fcd9968f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/class/cdc-acm.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 11da5fb284d0a..ca51230f44409 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -318,6 +318,16 @@ 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;
-- 
2.40.1