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)

Signed-off-by: Miguel García <miguelgarciaroman8@gmail.com>
---
v2:
  - Dropped third argument from strscpy(), inferred from field size.
v1: https://lore.kernel.org/netdev/20250811112207.97371-1-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

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)
> 
> Signed-off-by: Miguel García <miguelgarciaroman8@gmail.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Thanks Willem. Should I resend with your Reviewed-by tag or will it be
picked up when applied?

El mié, 13 ago 2025 a las 15:06, Willem de Bruijn
(<willemdebruijn.kernel@gmail.com>) escribió:
>
> 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)
> >
> > Signed-off-by: Miguel García <miguelgarciaroman8@gmail.com>
>
> Reviewed-by: Willem de Bruijn <willemb@google.com>

Miguel García Román wrote:
> Thanks Willem. Should I resend with your Reviewed-by tag or will it be
> picked up when applied?

No need. Also see other patches under review, and especially read

https://www.kernel.org/doc/html/next/process/submitting-patches.html

Note the comment on top posting.
 
> El mié, 13 ago 2025 a las 15:06, Willem de Bruijn
> (<willemdebruijn.kernel@gmail.com>) escribió:
> >
> > 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)
> > >
> > > Signed-off-by: Miguel García <miguelgarciaroman8@gmail.com>
> >
> > Reviewed-by: Willem de Bruijn <willemb@google.com>