Re: [PATCH 4/5] Input: tablet - replace strlcat() with strscpy()

[David Laight <david.laight.linux@gmail.com>]

On Sat, 17 Oct 2026 01:04:10 +0800
Shihuang Liu <shlomojune6@gmail.com> wrote:

> The acecad, aiptek, hanwang, kbtab and pegasus_notetaker drivers
> build the physical path by appending a constant "/input0" suffix
> with strlcat() after usb_make_path().
> 
> In preparation for removing the deprecated strlcat() API[1],
> replace it with strnlen() followed by strscpy() into the remainder
> of the buffer, as commit 34b228b739f5 ("HID: usbhid: replace
> strlcat with better alternatives") did for the usbhid drivers.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
> ---
>  drivers/input/tablet/acecad.c            | 4 +++-
>  drivers/input/tablet/aiptek.c            | 7 +++++--
>  drivers/input/tablet/hanwang.c           | 4 +++-
>  drivers/input/tablet/kbtab.c             | 4 +++-
>  drivers/input/tablet/pegasus_notetaker.c | 4 +++-
>  5 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/input/tablet/acecad.c b/drivers/input/tablet/acecad.c
> index ba79dff21aac8..8fec79c46d4b0 100644
> --- a/drivers/input/tablet/acecad.c
> +++ b/drivers/input/tablet/acecad.c
> @@ -117,6 +117,7 @@ static int usb_acecad_probe(struct usb_interface *intf, const struct usb_device_
>  	struct input_dev *input_dev;
>  	int pipe, maxp;
>  	int err;
> +	size_t len;
>  
>  	if (interface->desc.bNumEndpoints != 1)
>  		return -ENODEV;
> @@ -161,7 +162,8 @@ static int usb_acecad_probe(struct usb_interface *intf, const struct usb_device_
>  	}
>  
>  	usb_make_path(dev, acecad->phys, sizeof(acecad->phys));
> -	strlcat(acecad->phys, "/input0", sizeof(acecad->phys));
> +	len = strnlen(acecad->phys, sizeof(acecad->phys));
> +	strscpy(acecad->phys + len, "/input0", sizeof(acecad->phys) - len);

There is no point replacing strcat() with strlen() + strcpy()
(any variants of the functions).

David

>  
>  	input_dev->name = acecad->name;
>  	input_dev->phys = acecad->phys;
> diff --git a/drivers/input/tablet/aiptek.c b/drivers/input/tablet/aiptek.c
> index 0c1acb9e6b437..e868d0bac771d 100644
> --- a/drivers/input/tablet/aiptek.c
> +++ b/drivers/input/tablet/aiptek.c
> @@ -1637,6 +1637,7 @@ aiptek_probe(struct usb_interface *intf, const struct usb_device_id *id)
>  		AIPTEK_PROGRAMMABLE_DELAY_300
>  	};
>  	int err = -ENOMEM;
> +	size_t len;
>  
>  	/* programmableDelay is where the command-line specified
>  	 * delay is kept. We make it the first element of speeds[],
> @@ -1707,8 +1708,10 @@ aiptek_probe(struct usb_interface *intf, const struct usb_device_id *id)
>  	 */
>  	usb_make_path(usbdev, aiptek->features.usbPath,
>  			sizeof(aiptek->features.usbPath));
> -	strlcat(aiptek->features.usbPath, "/input0",
> -		sizeof(aiptek->features.usbPath));
> +	len = strnlen(aiptek->features.usbPath,
> +		      sizeof(aiptek->features.usbPath));
> +	strscpy(aiptek->features.usbPath + len, "/input0",
> +		sizeof(aiptek->features.usbPath) - len);
>  
>  	/* Set up client data, pointers to open and close routines
>  	 * for the input device.
> diff --git a/drivers/input/tablet/hanwang.c b/drivers/input/tablet/hanwang.c
> index fd5a7e761dcc4..a75d10dd2fc7d 100644
> --- a/drivers/input/tablet/hanwang.c
> +++ b/drivers/input/tablet/hanwang.c
> @@ -318,6 +318,7 @@ static int hanwang_probe(struct usb_interface *intf, const struct usb_device_id
>  	struct input_dev *input_dev;
>  	int error;
>  	int i;
> +	size_t len;
>  
>  	if (intf->cur_altsetting->desc.bNumEndpoints < 1)
>  		return -ENODEV;
> @@ -351,7 +352,8 @@ static int hanwang_probe(struct usb_interface *intf, const struct usb_device_id
>  	hanwang->dev = input_dev;
>  
>  	usb_make_path(dev, hanwang->phys, sizeof(hanwang->phys));
> -	strlcat(hanwang->phys, "/input0", sizeof(hanwang->phys));
> +	len = strnlen(hanwang->phys, sizeof(hanwang->phys));
> +	strscpy(hanwang->phys + len, "/input0", sizeof(hanwang->phys) - len);
>  
>  	strscpy(hanwang->name, hanwang->features->name, sizeof(hanwang->name));
>  	input_dev->name = hanwang->name;
> diff --git a/drivers/input/tablet/kbtab.c b/drivers/input/tablet/kbtab.c
> index 6ce70c8e2d7cc..79a5e217654b6 100644
> --- a/drivers/input/tablet/kbtab.c
> +++ b/drivers/input/tablet/kbtab.c
> @@ -113,6 +113,7 @@ static int kbtab_probe(struct usb_interface *intf, const struct usb_device_id *i
>  	struct kbtab *kbtab;
>  	struct input_dev *input_dev;
>  	int error = -ENOMEM;
> +	size_t len;
>  
>  	if (intf->cur_altsetting->desc.bNumEndpoints < 1)
>  		return -ENODEV;
> @@ -138,7 +139,8 @@ static int kbtab_probe(struct usb_interface *intf, const struct usb_device_id *i
>  	kbtab->dev = input_dev;
>  
>  	usb_make_path(dev, kbtab->phys, sizeof(kbtab->phys));
> -	strlcat(kbtab->phys, "/input0", sizeof(kbtab->phys));
> +	len = strnlen(kbtab->phys, sizeof(kbtab->phys));
> +	strscpy(kbtab->phys + len, "/input0", sizeof(kbtab->phys) - len);
>  
>  	input_dev->name = "KB Gear Tablet";
>  	input_dev->phys = kbtab->phys;
> diff --git a/drivers/input/tablet/pegasus_notetaker.c b/drivers/input/tablet/pegasus_notetaker.c
> index 85390ae423076..679600bd214e4 100644
> --- a/drivers/input/tablet/pegasus_notetaker.c
> +++ b/drivers/input/tablet/pegasus_notetaker.c
> @@ -277,6 +277,7 @@ static int pegasus_probe(struct usb_interface *intf,
>  	struct input_dev *input_dev;
>  	int error;
>  	int pipe;
> +	size_t len;
>  
>  	/* We control interface 0 */
>  	if (intf->cur_altsetting->desc.bInterfaceNumber >= 1)
> @@ -355,7 +356,8 @@ static int pegasus_probe(struct usb_interface *intf,
>  			 le16_to_cpu(dev->descriptor.idProduct));
>  
>  	usb_make_path(dev, pegasus->phys, sizeof(pegasus->phys));
> -	strlcat(pegasus->phys, "/input0", sizeof(pegasus->phys));
> +	len = strnlen(pegasus->phys, sizeof(pegasus->phys));
> +	strscpy(pegasus->phys + len, "/input0", sizeof(pegasus->phys) - len);
>  
>  	INIT_WORK(&pegasus->init, pegasus_init);
>