[PATCH net] tuntap: correctly handle error in tun_set_iff()

[Jason Wang <jasowang@redhat.com>]

Commit c8d68e6be1c3b242f1c598595830890b65cea64a (tuntap: multiqueue support)
only call free_netdev() on err in tun_set_iff(). This causes several issues:

- memory of tun security were leaked
- use after free since the flow gc timer was not deleted and the tfile were not
  detached

This patch solves the above issues.

Reported-by: Wannes Rombouts <wannes.rombouts@epitech.eu>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
The patch were also needed for stable 3.8+.
---
 drivers/net/tun.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a639de8..e5fb5d3 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1641,11 +1641,11 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 		INIT_LIST_HEAD(&tun->disabled);
 		err = tun_attach(tun, file, false);
 		if (err < 0)
-			goto err_free_dev;
+			goto err_free_flow;
 
 		err = register_netdevice(tun->dev);
 		if (err < 0)
-			goto err_free_dev;
+			goto err_detach;
 
 		if (device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
 		    device_create_file(&tun->dev->dev, &dev_attr_owner) ||
@@ -1689,6 +1689,11 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 	strcpy(ifr->ifr_name, tun->dev->name);
 	return 0;
 
+err_detach:
+	tun_detach_all(dev);
+err_free_flow:
+	tun_flow_uninit(tun);
+	security_tun_dev_free_security(tun->security);
  err_free_dev:
 	free_netdev(dev);
 	return err;
-- 
1.7.1