[PATCH 3.16 074/136] USB: serial: ti_usb_3410_5052: fix port-close races

Ben Hutchings
2019-12-17T00:58:23Z

From: Johan Hovold <johan@kernel.org>

commit 6f1d1dc8d540a9aa6e39b9cb86d3a67bbc1c8d8d upstream.

Fix races between closing a port and opening or closing another port on
the same device which could lead to a failure to start or stop the
shared interrupt URB. The latter could potentially cause a
use-after-free or worse in the completion handler on driver unbind.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/serial/ti_usb_3410_5052.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -542,7 +542,6 @@ static void ti_close(struct usb_serial_p
struct ti_port *tport;
int port_number;
int status;
- int do_unlock;
unsigned long flags;

tdev = usb_get_serial_data(port->serial);
@@ -569,16 +568,13 @@ static void ti_close(struct usb_serial_p
"%s - cannot send close port command, %d\n"
, __func__, status);

- /* if mutex_lock is interrupted, continue anyway */
- do_unlock = !mutex_lock_interruptible(&tdev->td_open_close_lock);
+ mutex_lock(&tdev->td_open_close_lock);
--tport->tp_tdev->td_open_port_count;
- if (tport->tp_tdev->td_open_port_count <= 0) {
+ if (tport->tp_tdev->td_open_port_count == 0) {
/* last port is closed, shut down interrupt urb */
usb_kill_urb(port->serial->port[0]->interrupt_in_urb);
- tport->tp_tdev->td_open_port_count = 0;
}
- if (do_unlock)
- mutex_unlock(&tdev->td_open_close_lock);
+ mutex_unlock(&tdev->td_open_close_lock);
}