linux-kernel - Re: [PATCH v7] gpio: virtuser: new virtual driver

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Message-ID: <c5799a51-b39b-49b7-89ef-9cec2509330a@moroto.mountain>
Date: Wed, 29 May 2024 17:32:46 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Kent Gibson <warthog618@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v7] gpio: virtuser: new virtual driver

On Mon, May 27, 2024 at 04:40:54PM +0200, Bartosz Golaszewski wrote:
> +static ssize_t
> +gpio_virtuser_sysfs_consumer_store(struct device *dev,
> +				   struct device_attribute *attr,
> +				   const char *buf, size_t len)
> +{
> +	struct gpio_virtuser_line_data *data = to_gpio_virtuser_data(attr);
> +	int ret;
> +
> +	if (strlen(buf) > GPIO_CONSUMER_NAME_MAX_LEN)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is off by one.  strlen() doesn't count the NUL terminator.

> +		return -EINVAL;
> +
> +	guard(mutex)(&data->consumer_lock);
> +
> +	ret = gpiod_set_consumer_name(data->desc, buf);
> +	if (ret)
> +		return ret;
> +
> +	sprintf(data->consumer, buf);
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It results in a buffer overflow here.

> +
> +	return len;
> +}

regards,
dan carpenter