net: Fix locking bug in netif_set_xps_queue

Smatch found a locking bug in netif_set_xps_queue in which we were not
releasing the lock in the case of an allocation failure.

This change corrects that so that we release the xps_map_mutex before
returning -ENOMEM in the case of an allocation failure.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -1882,8 +1882,10 @@ int netif_set_xps_queue(struct net_device *dev, struct cpumask *mask, u16 index)
 
 		if (!new_dev_maps)
 			new_dev_maps = kzalloc(maps_sz, GFP_KERNEL);
-		if (!new_dev_maps)
+		if (!new_dev_maps) {
+			mutex_unlock(&xps_map_mutex);
 			return -ENOMEM;
+		}
 
 		map = dev_maps ? xmap_dereference(dev_maps->cpu_map[cpu]) :
 				 NULL;