strncpy() is deprecated for NUL-terminated destination buffers; use
strscpy() instead. Since kzalloc() already zeroes out the destination
buffer, the potential NUL-padding by strncpy() is unnecessary. strscpy()
copies only the required characters and guarantees NUL-termination.

Since the destination buffer has a fixed length, strscpy() automatically
determines its size using sizeof() when the argument is omitted. This
makes an explicit sizeof() call unnecessary.

The source string is also NUL-terminated and meets the __must_be_cstr()
requirement of strscpy().

No functional changes intended.

Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/usb/gadget/legacy/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index b6a30d88a800..fcce84a726f2 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1615,7 +1615,7 @@ static int activate_ep_files (struct dev_data *dev)
 		mutex_init(&data->lock);
 		init_waitqueue_head (&data->wait);
 
-		strncpy (data->name, ep->name, sizeof (data->name) - 1);
+		strscpy(data->name, ep->name);
 		refcount_set (&data->count, 1);
 		data->dev = dev;
 		get_dev (dev);

On Thu, Mar 20, 2025 at 05:56:44PM +0100, Thorsten Blum wrote:
> strncpy() is deprecated for NUL-terminated destination buffers; use
> strscpy() instead. Since kzalloc() already zeroes out the destination
> buffer, the potential NUL-padding by strncpy() is unnecessary. strscpy()
> copies only the required characters and guarantees NUL-termination.

Looks right to me; thanks for the details!

> 
> Since the destination buffer has a fixed length, strscpy() automatically
> determines its size using sizeof() when the argument is omitted. This
> makes an explicit sizeof() call unnecessary.
> 
> The source string is also NUL-terminated and meets the __must_be_cstr()
> requirement of strscpy().
> 
> No functional changes intended.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>

Reviewed-by: Kees Cook <kees@kernel.org>


> ---
>  drivers/usb/gadget/legacy/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
> index b6a30d88a800..fcce84a726f2 100644
> --- a/drivers/usb/gadget/legacy/inode.c
> +++ b/drivers/usb/gadget/legacy/inode.c
> @@ -1615,7 +1615,7 @@ static int activate_ep_files (struct dev_data *dev)
>  		mutex_init(&data->lock);
>  		init_waitqueue_head (&data->wait);
>  
> -		strncpy (data->name, ep->name, sizeof (data->name) - 1);
> +		strscpy(data->name, ep->name);
>  		refcount_set (&data->count, 1);
>  		data->dev = dev;
>  		get_dev (dev);

-- 
Kees Cook