[PATCH 4.14 19/36] tty/serial: atmel: use port->name as name in request_irq()

Greg Kroah-Hartman
2018-06-14T14:35:32Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

commit 9594b5be7ec110ed11acec58fa94f3f293668c85 upstream.

I was puzzled while looking at /proc/interrupts and random things showed
up between reboots. This occurred more often but I realised it later. The
"correct" output should be:
|38: 11861 atmel-aic5 2 Level ttyS0

but I saw sometimes
|38: 6426 atmel-aic5 2 Level tty1

and accounted it wrongly as correct. This is use after free and the
former example randomly got the "old" pointer which pointed to the same
content. With SLAB_FREELIST_RANDOM and HARDENED I even got
|38: 7067 atmel-aic5 2 Level E=Started User Manager for UID 0

or other nonsense.
As it turns out the tty, pointer that is accessed in atmel_startup(), is
freed() before atmel_shutdown(). It seems to happen quite often that the
tty for ttyS0 is allocated and freed while ->shutdown is not invoked. I
don't do anything special - just a systemd boot :)

Use dev_name(&pdev->dev) as the IRQ name for request_irq(). This exists
as long as the driver is loaded so no use-after-free here.

Cc: stable@vger.kernel.org
Fixes: 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close")
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/atmel_serial.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1786,7 +1786,6 @@ static int atmel_startup(struct uart_por
{
struct platform_device *pdev = to_platform_device(port->dev);
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
- struct tty_struct *tty = port->state->port.tty;
int retval;

/*
@@ -1801,8 +1800,8 @@ static int atmel_startup(struct uart_por
* Allocate the IRQ
*/
retval = request_irq(port->irq, atmel_interrupt,
- IRQF_SHARED | IRQF_COND_SUSPEND,
- tty ? tty->name : "atmel_serial", port);
+ IRQF_SHARED | IRQF_COND_SUSPEND,
+ dev_name(&pdev->dev), port);
if (retval) {
dev_err(port->dev, "atmel_startup - Can't get irq\n");
return retval;