Re: [PATCH] gpio: Initialize gc->irq.domain before setting gc->to_irq

[Emil Velikov]

Hi Shreeya, all,

On 2021/11/09, Shreeya Patel wrote:
> There is a race in registering of gc->irq.domain when
> probing the I2C driver.
> This sometimes leads to a Kernel NULL pointer dereference
> in gpiochip_to_irq function which uses the domain variable.
> 
> To avoid this issue, set gc->to_irq after domain is
> initialized. This will make sure whenever gpiochip_to_irq
> is called, it has domain already initialized.
> 

What is stopping the next developer to moving the assignment to the
incorrect place? Aka should we add an inline comment about this?

<snip>

> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index abfbf546d159..9a6f7c265a91 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1512,7 +1512,6 @@ static int gpiochip_add_irqchip(struct gpio_chip *gc,
>  	if (gc->to_irq)
>  		chip_warn(gc, "to_irq is redefined in %s and you shouldn't rely on it\n", __func__);
>  

Move the warning alongside the assignment?

HTH
Emil