[NET]: Require CAP_NET_ADMIN to create tuntap devices.

The tuntap driver allows an admin to create persistent devices and
assign ownership of them to individual users. Unfortunately, relaxing
the permissions on the /dev/net/tun device node so that they can
actually use those devices will _also_ allow those users to create
arbitrary new devices of their own. This patch corrects that, and
adjusts the recommended permissions for the device node accordingly.

Signed-off-By: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a1ed2d983740..6c62d5c88268 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -490,6 +490,9 @@ static int tun_set_iff(struct file *file, struct ifreq *ifr)
 
                 err = -EINVAL;
 
+                if (!capable(CAP_NET_ADMIN))
+                        return -EPERM;
+
                 /* Set dev type */
                 if (ifr->ifr_flags & IFF_TUN) {
                         /* TUN device */