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

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

[Miguel García]

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

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);
 	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

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

[Willem de Bruijn]

[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
> 

[PATCH v2] net: tun: replace strcpy with strscpy for ifr_name

[Miguel García]

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

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)

v2:
- Dropped third argument from strscpy(), inferred from field size.

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..ad33b16224e2 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);
 	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);
 
 	ifr->ifr_flags = tun_flags(tun);
 
-- 
2.34.1

Re: [PATCH v2] net: tun: replace strcpy with strscpy for ifr_name

[Jakub Kicinski]

On Mon, 11 Aug 2025 22:33:29 +0200 Miguel García wrote:
> Replace the strcpy() calls that copy the device name into ifr->ifr_name
> with strscpy() to avoid potential overflows and guarantee NULL termination.
> 
> 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)
> 
> v2:
> - Dropped third argument from strscpy(), inferred from field size.

Please don't post new patches in reply to old ones. Please read:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
there are multiple other problems with your submissions.
Please fix and repost.
-- 
pw-bot: cr