[PATCH 4.9 44/63] netpoll: Fix device name check in netpoll_setup()

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Kaehlcke <mka@xxxxxxxxxxxx>

commit 0c3a8f8b8fabff4f3ad2dd7b95ae0e90cdd1aebb upstream.

Apparently netpoll_setup() assumes that netpoll.dev_name is a pointer
when checking if the device name is set:

if (np->dev_name) {
  ...

However the field is a character array, therefore the condition always
yields true. Check instead whether the first byte of the array has a
non-zero value.

Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/netpoll.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -666,7 +666,7 @@ int netpoll_setup(struct netpoll *np)
 	int err;
 
 	rtnl_lock();
-	if (np->dev_name) {
+	if (np->dev_name[0]) {
 		struct net *net = current->nsproxy->net_ns;
 		ndev = __dev_get_by_name(net, np->dev_name);
 	}