[PATCH 4.9 037/139] tty: hvcs: Dont NULL tty->driver_data until hvcs_cleanup()

Greg Kroah-Hartman
2020-10-27T14:04:51Z

From: Tyrel Datwyler <tyreld@linux.ibm.com>

[ Upstream commit 63ffcbdad738e3d1c857027789a2273df3337624 ]

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: 27bf7c43a19c ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/hvc/hvcs.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/hvc/hvcs.c b/drivers/tty/hvc/hvcs.c
index 3c4d7c2b4ade8..de05196738da5 100644
--- a/drivers/tty/hvc/hvcs.c
+++ b/drivers/tty/hvc/hvcs.c
@@ -1232,13 +1232,6 @@ 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) {
@@ -1254,6 +1247,13 @@ 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);
}

--
2.25.1