Re: [PATCH v2 2/2] serial: 8250_port: properly handle runtime PM in IRQ

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] serial: 8250: missing port->dev NULL check in serial8250_default_handle_irq()
--

commit 128116d52224b04215dd65b2f4f799e8c14bdec7
Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

serial: 8250_port: properly handle runtime PM in IRQ

This commit updates the 8250 driver IRQ handler to explicitly check the
runtime PM status before processing the interrupt. It returns immediately
if the device is powered off, assuming it is a shared interrupt.

> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index c0bcc0742a60c..1e62460b19ab9 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -1878,13 +1878,22 @@ EXPORT_SYMBOL_GPL(serial8250_handle_irq);
>  
>  static int serial8250_default_handle_irq(struct uart_port *port)
>  {
[ ... ]
> +	/* if driver suspended, return, probably shared interrupt */
> +	pm_status = pm_runtime_get_if_active(port->dev);

[Severity: High]
Will this trigger a kernel panic if the port has no associated device? 
Some ports, such as legacy ISA serial ports, might have a NULL port->dev. 
Calling pm_runtime_get_if_active() with a NULL pointer would unconditionally 
dereference it.

> +	if (!pm_status)
> +		return 0;
>  
>  	iir = serial_port_in(port, UART_IIR);
> -	return serial8250_handle_irq(port, iir);
> +	ret = serial8250_handle_irq(port, iir);
> +
> +	if (pm_status > 0)
> +		pm_runtime_put_autosuspend(port->dev);

[Severity: High]
Similarly, does this put operation need a check to ensure port->dev is valid
before passing it to pm_runtime_put_autosuspend()?

> +
> +	return ret;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260924122549.668680-1-andriy.shevchenko@linux.intel.com?part=2