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Subject: Re: [PATCH 2/3] gpio: Fix gpiochip_add_data_with_key() error path
To:     Geert Uytterhoeven <geert+renesas@glider.be>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc:     Benoit Parrot <bparrot@ti.com>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190328131349.18838-1-geert+renesas@glider.be>
 <20190328131349.18838-3-geert+renesas@glider.be>
From:   Mukesh Ojha <mojha@codeaurora.org>
Message-ID: <c7b93076-4016-5413-dc03-0be1965bf498@codeaurora.org>
Date:   Thu, 28 Mar 2019 21:01:37 +0530
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On 3/28/2019 6:43 PM, Geert Uytterhoeven wrote:
> The err_remove_chip block is too coarse, and may perform cleanup that
> must not be done.  E.g. if of_gpiochip_add() fails, of_gpiochip_remove()
> is still called, causing:
>
>      OF: ERROR: Bad of_node_put() on /soc/gpio@e6050000
>      CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 5.1.0-rc2-koelsch+ #407
>      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>      Workqueue: events deferred_probe_work_func
>      [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
>      [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
>      [<c07c1224>] (dump_stack) from [<c07c5a80>] (kobject_put+0x94/0xbc)
>      [<c07c5a80>] (kobject_put) from [<c0470420>] (gpiochip_add_data_with_key+0x8d8/0xa3c)
>      [<c0470420>] (gpiochip_add_data_with_key) from [<c0473738>] (gpio_rcar_probe+0x1d4/0x314)
>      [<c0473738>] (gpio_rcar_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
>
> and later, if a GPIO consumer tries to use a GPIO from a failed
> controller:
>
>      WARNING: CPU: 0 PID: 1 at lib/refcount.c:156 kobject_get+0x38/0x4c
>      refcount_t: increment on 0; use-after-free.
>      Modules linked in:
>      CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-rc2-koelsch+ #407
>      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>      [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
>      [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
>      [<c07c1224>] (dump_stack) from [<c0221580>] (__warn+0xd0/0xec)
>      [<c0221580>] (__warn) from [<c02215e0>] (warn_slowpath_fmt+0x44/0x6c)
>      [<c02215e0>] (warn_slowpath_fmt) from [<c07c58fc>] (kobject_get+0x38/0x4c)
>      [<c07c58fc>] (kobject_get) from [<c068b3ec>] (of_node_get+0x14/0x1c)
>      [<c068b3ec>] (of_node_get) from [<c0686f24>] (of_find_node_by_phandle+0xc0/0xf0)
>      [<c0686f24>] (of_find_node_by_phandle) from [<c0686fbc>] (of_phandle_iterator_next+0x68/0x154)
>      [<c0686fbc>] (of_phandle_iterator_next) from [<c0687fe4>] (__of_parse_phandle_with_args+0x40/0xd0)
>      [<c0687fe4>] (__of_parse_phandle_with_args) from [<c0688204>] (of_parse_phandle_with_args_map+0x100/0x3ac)
>      [<c0688204>] (of_parse_phandle_with_args_map) from [<c0471240>] (of_get_named_gpiod_flags+0x38/0x380)
>      [<c0471240>] (of_get_named_gpiod_flags) from [<c046f864>] (gpiod_get_from_of_node+0x24/0xd8)
>      [<c046f864>] (gpiod_get_from_of_node) from [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child+0xa0/0x144)
>      [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child) from [<c05f425c>] (gpio_keys_probe+0x418/0x7bc)
>      [<c05f425c>] (gpio_keys_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
>
> Fix this by splitting the cleanup block, and adding a missing call to
> gpiochip_irqchip_remove().
>
> Fixes: 28355f81969962cf ("gpio: defer probe if pinctrl cannot be found")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> I'm not so sure about the need for the call to
> gpiochip_irqchip_remove(), as add/remove are not really symmetrical.
> Any comments?
> ---
>   drivers/gpio/gpiolib.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 144af07335815998..ed4da07effe0ac40 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1379,7 +1379,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   
>   	status = gpiochip_add_irqchip(chip, lock_key, request_key);
>   	if (status)
> -		goto err_remove_chip;
> +		goto err_free_irqchip_mask;

Name is quite confusing
this should be

s/err_free_irqchip_mask/err_free_gpiochip_mask


>   
>   	status = of_gpiochip_add(chip);
>   	if (status)
> @@ -1387,7 +1387,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   
>   	status = gpiochip_init_valid_mask(chip);
>   	if (status)
> -		goto err_remove_chip;
> +		goto err_remove_of_chip;
>   
>   	for (i = 0; i < chip->ngpio; i++) {
>   		struct gpio_desc *desc = &gdev->descs[i];
> @@ -1415,14 +1415,18 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   	if (gpiolib_initialized) {
>   		status = gpiochip_setup_dev(gdev);
>   		if (status)
> -			goto err_remove_chip;
> +			goto err_remove_acpi_chip;
>   	}
>   	return 0;
>   
> -err_remove_chip:
> +err_remove_acpi_chip:
>   	acpi_gpiochip_remove(chip);
> +err_remove_of_chip:
>   	gpiochip_free_hogs(chip);
>   	of_gpiochip_remove(chip);
> +err_remove_chip:
> +	gpiochip_irqchip_remove(chip);
> +err_free_irqchip_mask:


same here.

After reviewing back and forth it looks good, apart from the naming.
Please fix.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

-Mukesh


>   	gpiochip_free_valid_mask(chip);
>   err_remove_irqchip_mask:
>   	gpiochip_irqchip_free_valid_mask(chip);