On 04/05/2018 10:14, Sebastian Andrzej Siewior wrote:
> 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 port->name as the IRQ name for request_irq(). This exists as long as
> the driver is loaded so no use-after-free here.
> For backports before v4.12 I suggest to use `"atmel_serial"' instead
> `port->name' (that member was introduced in f7048b15900f ("tty: serial_core:
> Add name field to uart_port struct").
>
> Cc: stable@xxxxxxxxxxxxxxx
I think it's safer to use:
Cc: stable@xxxxxxxxxxxxxxx # 4.14
Because the stable team may miss your comment, and even if they don't, I
think it's not their role to adapt the patch to 4.9.x (and test it !)
IMHO, the best way is to add # 4.14 and when it's applied on 4.14.x,
send a tested backport for 4.9.x
Besides that, you can add my:
Acked-by: Richard Genoud <richard.genoud@xxxxxxxxx>
Rob, do you agree with this fix ?
> Fixes: 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> v1…v2: - Bisected and added a Fixes tag
> - added a note for backporters to v4.9 … v4.12 (pointed out by
> Richard Genoud)
>
> drivers/tty/serial/atmel_serial.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index e287fe8f10fc..d3189816740e 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -1757,7 +1757,6 @@ static int atmel_startup(struct uart_port *port)
> {
> 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;
>
> /*
> @@ -1772,8 +1771,7 @@ static int atmel_startup(struct uart_port *port)
> * 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, port->name, port);
> if (retval) {
> dev_err(port->dev, "atmel_startup - Can't get irq\n");
> return retval;
>
Thanks !
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