Re: [PATCH] gpio: cdev: avoid uninitialized variable dereference

["Arnd Bergmann" <arnd@xxxxxxxx>]

On Fri, Feb 16, 2024, at 16:51, Paul E. McKenney wrote:
> On Fri, Feb 16, 2024 at 03:04:14PM +0100, Arnd Bergmann wrote:
>> On Fri, Feb 16, 2024, at 14:19, Bartosz Golaszewski wrote:
>> > On Fri, Feb 16, 2024 at 2:00 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>> >>
>> >> From: Arnd Bergmann <arnd@xxxxxxxx>
>> >>
>> >> The 'gc' variable is never set before it gets printed:
>> >>
>> >> drivers/gpio/gpiolib-cdev.c:2802:11: error: variable 'gc' is uninitialized when used here [-Werror,-Wuninitialized]
>> >>  2802 |         chip_dbg(gc, "added GPIO chardev (%d:%d)\n", MAJOR(devt), gdev->id);
>> >>       |                  ^~
>> >> drivers/gpio/gpiolib.h:277:11: note: expanded from macro 'chip_dbg'
>> >>   277 |         dev_dbg(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
>> >>       |                  ^~
>> >>
>> >> Use dev_dbg() directly.
>> >>
>> >> Fixes: 8574b5b47610 ("gpio: cdev: use correct pointer accessors with SRCU")
>> >> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>> >> ---
>> >
>> > I seem to have beat you to it[1] and my patch doesn't change the log
>> > message so I'll apply it instead of this one.
>> 
>> Ok, thanks. I thought about doing this, but could not
>> figure out which of the RCU primitives to use.
>
> I will count that as a bug against RCU's documentation, but I am not
> sure how to fix it.  Thoughts?

I didn't really try at all, I just figured I could avoid
thinking about it by using the device pointer at hand.

I'm sure the docs would have told me if I had bothered to look.

     Arnd