Re: [PATCH] net: tun: replace strcpy with strscpy for ifr_name

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

[PATCH net-next]

Miguel García wrote:
> Replace the strcpy() calls that copy the device name into ifr->ifr_name
> with strscpy() to avoid potential overflows and guarantee NUL termination.

NULL

> Destination is ifr->ifr_name (size IFNAMSIZ).
> 
> Tested in QEMU (BusyBox rootfs):
>  - Created TUN devices via TUNSETIFF helper
>  - Set addresses and brought links up
>  - Verified long interface names are safely truncated (IFNAMSIZ-1)
> 
> Signed-off-by: Miguel García <miguelgarciaroman8@gmail.com>
> ---
>  drivers/net/tun.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index f8c5e2fd04df..e4c6c1118acb 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2800,13 +2800,13 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>  	if (netif_running(tun->dev))
>  		netif_tx_wake_all_queues(tun->dev);
>  
> -	strcpy(ifr->ifr_name, tun->dev->name);
> +	strscpy(ifr->ifr_name, tun->dev->name, IFNAMSIZ);

Since both dst and src are arrays of IFNAMSIZ, can drop the third
argument. Then it is inferred from the field sizes, which is more
robust.

>  	return 0;
>  }
>  
>  static void tun_get_iff(struct tun_struct *tun, struct ifreq *ifr)
>  {
> -	strcpy(ifr->ifr_name, tun->dev->name);
> +	strscpy(ifr->ifr_name, tun->dev->name, IFNAMSIZ);
>  
>  	ifr->ifr_flags = tun_flags(tun);
>  
> -- 
> 2.34.1
>