linux-kernel - Re: [PATCH] USB: gadget: Replace deprecated strncpy() with strscpy()

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Message-ID: <202504071153.46436ACBB@keescook>
Date: Mon, 7 Apr 2025 11:54:08 -0700
From: Kees Cook <kees@...nel.org>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Al Viro <viro@...iv.linux.org.uk>, linux-hardening@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: gadget: Replace deprecated strncpy() with strscpy()

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@...r.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>

Reviewed-by: Kees Cook <kees@...nel.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