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Date: Thu, 1 Feb 2024 08:57:44 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: oe-kbuild@...ts.linux.dev, Linus Walleij <linus.walleij@...aro.org>,
Kent Gibson <warthog618@...il.com>, Alex Elder <elder@...aro.org>,
Geert Uytterhoeven <geert+renesas@...der.be>, "Paul E . McKenney" <paulmck@...nel.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Wolfram Sang <wsa-dev@...g-engineering.com>, lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 20/22] gpio: protect the pointer to gpio_chip in
gpio_device with SRCU
On Thu, Feb 1, 2024 at 6:03 AM Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> Hi Bartosz,
>
> kernel test robot noticed the following build warnings:
>
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Bartosz-Golaszewski/gpio-protect-the-list-of-GPIO-devices-with-SRCU/20240130-205537
> base: https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git gpio/for-next
> patch link: https://lore.kernel.org/r/20240130124828.14678-21-brgl%40bgdev.pl
> patch subject: [PATCH 20/22] gpio: protect the pointer to gpio_chip in gpio_device with SRCU
> config: i386-randconfig-141-20240131 (https://download.01.org/0day-ci/archive/20240201/202402010641.idtEaO24-lkp@intel.com/config)
> compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> | Closes: https://lore.kernel.org/r/202402010641.idtEaO24-lkp@intel.com/
>
> New smatch warnings:
> drivers/gpio/gpiolib.c:4776 gpiolib_dbg_show() error: we previously assumed 'gc' could be null (see line 4773)
>
>
> vim +/gc +4776 drivers/gpio/gpiolib.c
>
> fdeb8e1547cb9d Linus Walleij 2016-02-10 4762 static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
> d2876d08d86f22 David Brownell 2008-02-04 4763 {
> 0338f6a6fb659f Bartosz Golaszewski 2023-12-21 4764 bool active_low, is_irq, is_out;
> 0338f6a6fb659f Bartosz Golaszewski 2023-12-21 4765 unsigned int gpio = gdev->base;
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4766 struct gpio_desc *desc;
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 4767 struct gpio_chip *gc;
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4768 int value;
> d2876d08d86f22 David Brownell 2008-02-04 4769
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 4770 guard(srcu)(&gdev->srcu);
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 4771
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 4772 gc = rcu_dereference(gdev->chip);
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 @4773 if (!gc)
> ^^^
> The patch adds a NULL check
>
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 4774 seq_puts(s, "Underlying GPIO chip is gone\n");
> 2796d5332f8ac8 Bartosz Golaszewski 2024-01-30 4775
> 3de69ae1c407da Andy Shevchenko 2022-04-08 @4776 for_each_gpio_desc(gc, desc) {
> ^^
> But this dereference isn't checked... Probably it should return after
> the seq_puts().
>
Of course it should. Thanks. I fixed it for v2.
Bart
> bedc56b1695b27 Bartosz Golaszewski 2024-01-30 4777 guard(srcu)(&desc->srcu);
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4778 if (test_bit(FLAG_REQUESTED, &desc->flags)) {
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4779 gpiod_get_direction(desc);
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4780 is_out = test_bit(FLAG_IS_OUT, &desc->flags);
> 234c52097ce416 Andy Shevchenko 2022-04-08 4781 value = gpio_chip_get_value(gc, desc);
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4782 is_irq = test_bit(FLAG_USED_AS_IRQ, &desc->flags);
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4783 active_low = test_bit(FLAG_ACTIVE_LOW, &desc->flags);
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4784 seq_printf(s, " gpio-%-3d (%-20.20s|%-20.20s) %s %s %s%s\n",
> 32648f473c7f46 Bartosz Golaszewski 2024-01-30 4785 gpio, desc->name ?: "", gpiod_get_label(desc),
> d2876d08d86f22 David Brownell 2008-02-04 4786 is_out ? "out" : "in ",
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4787 value >= 0 ? (value ? "hi" : "lo") : "? ",
> 90fd227029a25b Linus Walleij 2018-10-01 4788 is_irq ? "IRQ " : "",
> 90fd227029a25b Linus Walleij 2018-10-01 4789 active_low ? "ACTIVE LOW" : "");
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4790 } else if (desc->name) {
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4791 seq_printf(s, " gpio-%-3d (%-20.20s)\n", gpio, desc->name);
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4792 }
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4793
> 3de69ae1c407da Andy Shevchenko 2022-04-08 4794 gpio++;
> d2876d08d86f22 David Brownell 2008-02-04 4795 }
> d2876d08d86f22 David Brownell 2008-02-04 4796 }
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
>
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