Commit 63ffcbda authored Aug 20, 2020 by Tyrel Datwyler Committed by Greg Kroah-Hartman Sep 04, 2020

tty: hvcs: Don't NULL tty->driver_data until hvcs_cleanup()



The code currently NULLs tty->driver_data in hvcs_close() with the
intent of informing the next call to hvcs_open() that device needs to be
reconfigured. However, when hvcs_cleanup() is called we copy hvcsd from
tty->driver_data which was previoulsy NULLed by hvcs_close() and our
call to tty_port_put(&hvcsd->port) doesn't actually do anything since
&hvcsd->port ends up translating to NULL by chance. This has the side
effect that when hvcs_remove() is called we have one too many port
references preventing hvcs_destuct_port() from ever being called. This
also prevents us from reusing the /dev/hvcsX node in a future
hvcs_probe() and we can eventually run out of /dev/hvcsX devices.

Fix this by waiting to NULL tty->driver_data in hvcs_cleanup().

Fixes: 27bf7c43 ("TTY: hvcs, add tty install")
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Link: https://lore.kernel.org/r/20200820234643.70412-1-tyreld@linux.ibm.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent db332356

drivers/tty/hvc/hvcs.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -1216,13 +1216,6 @@ static void hvcs_close(struct tty_struct tty, struct file filp)

		tty_wait_until_sent(tty, HVCS_CLOSE_WAIT);

		/*
		* This line is important because it tells hvcs_open that this
		* device needs to be re-configured the next time hvcs_open is
		* called.
		*/
		tty->driver_data = NULL;

		free_irq(irq, hvcsd);
		return;
		} else if (hvcsd->port.count < 0) {
		@@ -1237,6 +1230,13 @@ static void hvcs_cleanup(struct tty_struct * tty)
		{
		struct hvcs_struct *hvcsd = tty->driver_data;

		/*
		* This line is important because it tells hvcs_open that this
		* device needs to be re-configured the next time hvcs_open is
		* called.
		*/
		tty->driver_data = NULL;

		tty_port_put(&hvcsd->port);
		}