vxlan: fix oops when give unknown ifindex

If vxlan is created and the ifindex is passed; there are two cases which
are incorrectly handled by the existing code. The ifindex could be zero
(i.e. no device) or there could be no device with that ifindex.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 6 deletions

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 763061d97921..607976c00162 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1090,14 +1090,18 @@ static int vxlan_newlink(struct net *net, struct net_device *dev,
         if (data[IFLA_VXLAN_LOCAL])
                 vxlan->saddr = nla_get_be32(data[IFLA_VXLAN_LOCAL]);
 
-        if (data[IFLA_VXLAN_LINK]) {
-                vxlan->link = nla_get_u32(data[IFLA_VXLAN_LINK]);
+        if (data[IFLA_VXLAN_LINK] &&
+            (vxlan->link = nla_get_u32(data[IFLA_VXLAN_LINK]))) {
+                struct net_device *lowerdev
+                         = __dev_get_by_index(net, vxlan->link);
+
+                if (!lowerdev) {
+                        pr_info("ifindex %d does not exist\n", vxlan->link);
+                        return -ENODEV;
+                }
 
-                if (!tb[IFLA_MTU]) {
-                        struct net_device *lowerdev;
-                        lowerdev = __dev_get_by_index(net, vxlan->link);
+                if (!tb[IFLA_MTU])
                         dev->mtu = lowerdev->mtu - VXLAN_HEADROOM;
-                }
         }
 
         if (data[IFLA_VXLAN_TOS])