xhci: dbgtty: fix device unregister

When DbC is disconnected then xhci_dbc_tty_unregister_device()
is called. However if there is any user space process blocked
on write to DbC terminal device then it will never be signalled
and thus stay blocked indifinitely.

This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device().
The tty_vhangup() wakes up any blocked writers and causes subsequent
write attempts to DbC terminal device to fail.

Cc: stable <stable@kernel.org>
Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver")
Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
Link: https://patch.msgid.link/20251119212910.1245694-1-ukaszb@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index b7f95565524d9b30770dcdb4de361eb97c8ac271..57cdda4e09c8ea74d3810e8009e2010a181efa19 100644 (file)
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -550,6 +550,12 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 
        if (!port->registered)
                return;
+       /*
+        * Hang up the TTY. This wakes up any blocked
+        * writers and causes subsequent writes to fail.
+        */
+       tty_vhangup(port->port.tty);
+
        tty_unregister_device(dbc_tty_driver, port->minor);
        xhci_dbc_tty_exit_port(port);
        port->registered = false;