tty: Prevent tty_port destruction if tty not released

If the tty driver mistakenly drops the last port reference
before the tty has been released, issue a diagnostic and
abort the port destruction.

This will leak memory and may zombify the port, but might
otherwise keep the machine in runnable state.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index f597e88a705d1fa8e65cf36ae98a61f84f20b9a3..7efbca474689ea93fa776436b2bb319033539056 100644 (file)
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -140,6 +140,10 @@ EXPORT_SYMBOL(tty_port_destroy);
 static void tty_port_destructor(struct kref *kref)
 {
        struct tty_port *port = container_of(kref, struct tty_port, kref);
+
+       /* check if last port ref was dropped before tty release */
+       if (WARN_ON(port->itty))
+               return;
        if (port->xmit_buf)
                free_page((unsigned long)port->xmit_buf);
        tty_port_destroy(port);