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

[Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>]

Emil Velikov <emil.velikov@xxxxxxxxxxxxx> writes:

> 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?

I agree with Emil.  The patch seems like a workaround that doesn't
really solve the underlying issue.  I'm not familiar with this code, but
it seems that gc is missing a lock during this initialization, to prevent
it from exposing a partially initialized gc->irq.

-- 
Gabriel Krisman Bertazi