netpoll: prevent netpoll setup on slave devices

In commit 8d8fc29d02a33e4bd5f4fa47823c1fd386346093
(netpoll: disable netpoll when enslave a device), we automatically
disable netpoll when the underlying device is being enslaved,
we also need to prevent people from setuping netpoll on
devices that are already enslaved.

Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 2d7d6d473781..42ea4b0e59f1 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -792,6 +792,12 @@ int netpoll_setup(struct netpoll *np)
                 return -ENODEV;
         }
 
+        if (ndev->master) {
+                printk(KERN_ERR "%s: %s is a slave device, aborting.\n",
+                       np->name, np->dev_name);
+                return -EBUSY;
+        }
+
         if (!netif_running(ndev)) {
                 unsigned long atmost, atleast;