net: Allow userns root to control tun and tap devices

Allow an unpriviled user who has created a user namespace, and then created a network namespace to effectively use the new network namespace, by reducing capable(CAP_NET_ADMIN) calls to ns_capable(net->user_ns,CAP_NET_ADMIN) calls.

Allow setting of the tun iff flags.
Allow creating of tun devices.
Allow adding a new queue to a tun device.

Signed-off-by "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/[email protected]>

---
 drivers/net/tun.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

drivers/net/tun.c +3 -2

index b44d7b7..b01e8c0 100644
@@ -373,10 +373,11 @@ static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb)
 static inline bool tun_not_capable(struct tun_struct *tun)
 {
 	const struct cred *cred = current_cred();
+	struct net *net = dev_net(tun->dev);
 
 	return ((uid_valid(tun->owner) && !uid_eq(cred->euid, tun->owner)) ||
 		  (gid_valid(tun->group) && !in_egroup_p(tun->group))) &&
-		!capable(CAP_NET_ADMIN);
+		!ns_capable(net->user_ns, CAP_NET_ADMIN);
 }
 
 static void tun_set_real_num_queues(struct tun_struct *tun)

@@ -1559,7 +1560,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 		char *name;
 		unsigned long flags = 0;
 
-		if (!capable(CAP_NET_ADMIN))
+		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 			return -EPERM;
 		err = security_tun_dev_create();
 		if (err < 0)

Signature · 1 line

1.7.5.4

Quoted 6 lines

Allow an unpriviled user who has created a user namespace, and then created a network namespace to effectively use the new network namespace, by reducing capable(CAP_NET_ADMIN) calls to ns_capable(net->user_ns,CAP_NET_ADMIN) calls.

Quoted 4 lines

Allow setting of the tun iff flags.
Allow creating of tun devices.
Allow adding a new queue to a tun device.

Acked-by Serge Hallyn <[email protected]>