netconsole: enable netconsole can make net_device refcnt incorrent

There is no check if netconsole is enabled current.
so when exec echo 1 > enabled;
the reference of net_device will increment always.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index ed2a3977c6e7..e8882023576b 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -307,6 +307,11 @@ static ssize_t store_enabled(struct netconsole_target *nt,
                 return err;
         if (enabled < 0 || enabled > 1)
                 return -EINVAL;
+        if (enabled == nt->enabled) {
+                printk(KERN_INFO "netconsole: network logging has already %s\n",
+                                nt->enabled ? "started" : "stopped");
+                return -EINVAL;
+        }
 
         if (enabled) {  /* 1 */