linux-kernel - Re: [PATCH] gpio: cdev: avoid uninitialized variable dereference

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Message-ID: <a3bc8b0f-7f14-4b46-a432-d3688104f11a@paulmck-laptop>
Date: Fri, 16 Feb 2024 08:50:00 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Bartosz Golaszewski <brgl@...ev.pl>, Arnd Bergmann <arnd@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Kent Gibson <warthog618@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: cdev: avoid uninitialized variable dereference

On Fri, Feb 16, 2024 at 05:17:06PM +0100, Arnd Bergmann wrote:
> 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@...nel.org> wrote:
> >> >>
> >> >> From: Arnd Bergmann <arnd@...db.de>
> >> >>
> >> >> 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@...db.de>
> >> >> ---
> >> >
> >> > 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.

OK, a low-priority bug against RCU's documentation, then.  ;-)

							Thanx, paul