xfrm: fix netdev reference count imbalance

In cited commit, netdev_tracker_alloc() is called for the newly
allocated xfrm state, but dev_hold() is missed, which causes netdev
reference count imbalance, because netdev_put() is called when the
state is freed in xfrm_dev_state_free(). Fix the issue by replacing
netdev_tracker_alloc() with netdev_hold().

Fixes: f8a70af ("xfrm: add TX datapath support for IPsec packet offload mode")
Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

Author: Jianbo Liu

net/xfrm/xfrm_state.c

@@ -1331,8 +1331,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
 			xso->dev = xdo->dev;
 			xso->real_dev = xdo->real_dev;
 			xso->flags = XFRM_DEV_OFFLOAD_FLAG_ACQ;
-			netdev_tracker_alloc(xso->dev, &xso->dev_tracker,
-					     GFP_ATOMIC);
+			netdev_hold(xso->dev, &xso->dev_tracker, GFP_ATOMIC);
 			error = xso->dev->xfrmdev_ops->xdo_dev_state_add(x, NULL);
 			if (error) {
 				xso->dir = 0;