ip6_tunnel: fix error code when tunnel exists

After commit 2b0bb01b6edb, the kernel returns -ENOBUFS when user tries to add
an existing tunnel with ioctl API:
$ ip -6 tunnel add ip6tnl1 mode ip6ip6 dev eth1
add tunnel "ip6tnl0" failed: No buffer space available

It's confusing, the right error is EEXIST.

This patch also change a bit the code returned:
 - ENOBUFS -> ENOMEM
 - ENOENT -> ENODEV

Fixes: 2b0bb01b6edb ("ip6_tunnel: Return an error when adding an existing tunnel.")
CC: Steffen Klassert <steffen.klassert@secunet.com>
Reported-by: Pierre Cheynier <me@pierre-cheynier.net>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 16 deletions

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 266a264ec212..ddd94eca19b3 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -314,7 +314,7 @@ out:
  *   Create tunnel matching given parameters.
  *
  * Return:
- *   created tunnel or NULL
+ *   created tunnel or error pointer
  **/
 
 static struct ip6_tnl *ip6_tnl_create(struct net *net, struct __ip6_tnl_parm *p)
@@ -322,7 +322,7 @@ static struct ip6_tnl *ip6_tnl_create(struct net *net, struct __ip6_tnl_parm *p)
         struct net_device *dev;
         struct ip6_tnl *t;
         char name[IFNAMSIZ];
-        int err;
+        int err = -ENOMEM;
 
         if (p->name[0])
                 strlcpy(name, p->name, IFNAMSIZ);
@@ -348,7 +348,7 @@ static struct ip6_tnl *ip6_tnl_create(struct net *net, struct __ip6_tnl_parm *p)
 failed_free:
         ip6_dev_free(dev);
 failed:
-        return NULL;
+        return ERR_PTR(err);
 }
 
 /**
@@ -362,7 +362,7 @@ failed:
  *   tunnel device is created and registered for use.
  *
  * Return:
- *   matching tunnel or NULL
+ *   matching tunnel or error pointer
  **/
 
 static struct ip6_tnl *ip6_tnl_locate(struct net *net,
@@ -380,13 +380,13 @@ static struct ip6_tnl *ip6_tnl_locate(struct net *net,
                 if (ipv6_addr_equal(local, &t->parms.laddr) &&
                     ipv6_addr_equal(remote, &t->parms.raddr)) {
                         if (create)
-                                return NULL;
+                                return ERR_PTR(-EEXIST);
 
                         return t;
                 }
         }
         if (!create)
-                return NULL;
+                return ERR_PTR(-ENODEV);
         return ip6_tnl_create(net, p);
 }
 
@@ -1420,7 +1420,7 @@ ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
                         }
                         ip6_tnl_parm_from_user(&p1, &p);
                         t = ip6_tnl_locate(net, &p1, 0);
-                        if (t == NULL)
+                        if (IS_ERR(t))
                                 t = netdev_priv(dev);
                 } else {
                         memset(&p, 0, sizeof(p));
@@ -1445,7 +1445,7 @@ ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
                 ip6_tnl_parm_from_user(&p1, &p);
                 t = ip6_tnl_locate(net, &p1, cmd == SIOCADDTUNNEL);
                 if (cmd == SIOCCHGTUNNEL) {
-                        if (t != NULL) {
+                        if (!IS_ERR(t)) {
                                 if (t->dev != dev) {
                                         err = -EEXIST;
                                         break;
@@ -1457,14 +1457,15 @@ ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
                         else
                                 err = ip6_tnl_update(t, &p1);
                 }
-                if (t) {
+                if (!IS_ERR(t)) {
                         err = 0;
                         ip6_tnl_parm_to_user(&p, &t->parms);
                         if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
                                 err = -EFAULT;
 
-                } else
-                        err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
+                } else {
+                        err = PTR_ERR(t);
+                }
                 break;
         case SIOCDELTUNNEL:
                 err = -EPERM;
@@ -1478,7 +1479,7 @@ ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
                         err = -ENOENT;
                         ip6_tnl_parm_from_user(&p1, &p);
                         t = ip6_tnl_locate(net, &p1, 0);
-                        if (t == NULL)
+                        if (IS_ERR(t))
                                 break;
                         err = -EPERM;
                         if (t->dev == ip6n->fb_tnl_dev)
@@ -1672,12 +1673,13 @@ static int ip6_tnl_newlink(struct net *src_net, struct net_device *dev,
                            struct nlattr *tb[], struct nlattr *data[])
 {
         struct net *net = dev_net(dev);
-        struct ip6_tnl *nt;
+        struct ip6_tnl *nt, *t;
 
         nt = netdev_priv(dev);
         ip6_tnl_netlink_parms(data, &nt->parms);
 
-        if (ip6_tnl_locate(net, &nt->parms, 0))
+        t = ip6_tnl_locate(net, &nt->parms, 0);
+        if (!IS_ERR(t))
                 return -EEXIST;
 
         return ip6_tnl_create2(dev);
@@ -1697,8 +1699,7 @@ static int ip6_tnl_changelink(struct net_device *dev, struct nlattr *tb[],
         ip6_tnl_netlink_parms(data, &p);
 
         t = ip6_tnl_locate(net, &p, 0);
-
-        if (t) {
+        if (!IS_ERR(t)) {
                 if (t->dev != dev)
                         return -EEXIST;
         } else