Re: [PATCH] gpiolib: cdev: fix NULL-pointer dereferences

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Fri, Nov 25, 2022 at 05:48:02PM +0100, Bartosz Golaszewski wrote:
> On Fri, Nov 25, 2022 at 5:24 PM Kent Gibson <warthog618@xxxxxxxxx> wrote:

...

> Then at the subsystem level, the GPIO device struct would need a lock
> that would be taken by every user-space operation AND the code
> unregistering the device so that we don't do what you described (i.e.
> if there's a thread doing a read(), then let's wait until it returns
> before we drop the device).

It's called a reference counting, basically you need to get device and then
put when it makes sense.

> This wouldn't fix the case in which the same situation happened in a
> kernel driver but crashing the kernel from within is a much lesser
> offense than allowing user-space to crash it.

-- 
With Best Regards,
Andy Shevchenko