linux-kernel - Re: [PATCH 01/23] gpiolib: Correct wrong kfree() usage for `kobj->name`

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Message-ID: <20260116141356.GI961588@nvidia.com>
Date: Fri, 16 Jan 2026 10:13:56 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Tzung-Bi Shih <tzungbi@...nel.org>
Cc: Benson Leung <bleung@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Linus Walleij <linusw@...nel.org>, Jonathan Corbet <corbet@....net>,
	Shuah Khan <shuah@...nel.org>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev,
	linux-kselftest@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Simona Vetter <simona.vetter@...ll.ch>,
	Dan Williams <dan.j.williams@...el.com>, linux-gpio@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 01/23] gpiolib: Correct wrong kfree() usage for
 `kobj->name`

On Fri, Jan 16, 2026 at 08:10:14AM +0000, Tzung-Bi Shih wrote:
> `kobj->name` should be freed by kfree_const()[1][2].  Correct it.
> 
> [1] https://elixir.bootlin.com/linux/v6.18/source/lib/kasprintf.c#L41
> [2] https://elixir.bootlin.com/linux/v6.18/source/lib/kobject.c#L695
> 
> Cc: stable@...r.kernel.org
> Fixes: c351bb64cbe6 ("gpiolib: free device name on error path to fix kmemleak")
> Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
> ---
>  drivers/gpio/gpiolib.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 5eb918da7ea2..ba9323432e3a 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1263,7 +1263,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>  err_free_descs:
>  	kfree(gdev->descs);
>  err_free_dev_name:
> -	kfree(dev_name(&gdev->dev));
> +	kfree_const(dev_name(&gdev->dev));
>  err_free_ida:
>  	ida_free(&gpio_ida, gdev->id);
>  err_free_gdev:
        kfree(gdev);

I don't think users should be open coding this, put_device() frees the
dev_name properly. The issue here is that the code doesn't call
device_initialize() before doing dev_set_name() and then tries to
fiddle a weird teardown sequence when it eventually does get initialized:

err_remove_from_list:
        if (gdev->dev.release) {
                /* release() has been registered by gpiochip_setup_dev() */
                gpio_device_put(gdev);
                goto err_print_message;
        }

If gpiochip_add_data_with_key() is split into two functions, one that
does kzalloc(), some initialization and then ends with
device_initialize(), then a second function that calls the first and
does the rest of the initialization and error unwinds with
put_device() it will work a lot better.

Jason