xfrm: use net device refcount tracker helpers

xfrm4_fill_dst() and xfrm6_fill_dst() build dst,
getting a device reference that will likely be released
by standard dst_release() code.

We have to track these references or risk a warning if
CONFIG_NET_DEV_REFCNT_TRACKER=y

Note to XFRM maintainers :

Error path in xfrm6_fill_dst() releases the reference,
but does not clear xdst->u.dst.dev, so I wonder
if this could lead to double dev_put() in some cases,
where a dst_release() _is_ called by the callers in their
error path.

This extra dev_put() was added in commit 84c4a9df ("xfrm6:
release dev before returning error")

Fixes: 9038c320 ("net: dst: add net device refcount tracking to dst_entry")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <amwang@redhat.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Link: https://lore.kernel.org/r/20211207193203.2706158-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/xfrm4_policy.c

@@ -77,7 +77,7 @@ static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
 	xdst->u.rt.rt_iif = fl4->flowi4_iif;
 
 	xdst->u.dst.dev = dev;
-	dev_hold(dev);
+	dev_hold_track(dev, &xdst->u.dst.dev_tracker, GFP_ATOMIC);
 
 	/* Sheit... I remember I did this right. Apparently,
 	 * it was magically lost, so this code needs audit */

net/ipv6/xfrm6_policy.c

@@ -74,11 +74,11 @@ static int xfrm6_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
 	struct rt6_info *rt = (struct rt6_info *)xdst->route;
 
 	xdst->u.dst.dev = dev;
-	dev_hold(dev);
+	dev_hold_track(dev, &xdst->u.dst.dev_tracker, GFP_ATOMIC);
 
 	xdst->u.rt6.rt6i_idev = in6_dev_get(dev);
 	if (!xdst->u.rt6.rt6i_idev) {
-		dev_put(dev);
+		dev_put_track(dev, &xdst->u.dst.dev_tracker);
 		return -ENODEV;
 	}