ipv6: Fix memleak of nhc_pcpu_rth_output in fib_check_nh_v6_gw().

fib_check_nh_v6_gw() expects that fib6_nh_init() cleans up everything
when it fails.

Commit 7dd7316 ("ipv6: Always allocate pcpu memory in a fib6_nh")
moved fib_nh_common_init() before alloc_percpu_gfp() within fib6_nh_init()
but forgot to add cleanup for fib6_nh->nh_common.nhc_pcpu_rth_output in
case it fails to allocate fib6_nh->rt6i_pcpu, resulting in memleak.

Let's call fib_nh_common_release() and clear nhc_pcpu_rth_output in the
error path.

Note that we can remove the fib6_nh_release() call in nh_create_ipv6()
later in net-next.git.

Fixes: 7dd7316 ("ipv6: Always allocate pcpu memory in a fib6_nh")
Signed-off-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: q2ven

net/ipv6/route.c

@@ -3644,7 +3644,8 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
 		in6_dev_put(idev);
 
 	if (err) {
-		lwtstate_put(fib6_nh->fib_nh_lws);
+		fib_nh_common_release(&fib6_nh->nh_common);
+		fib6_nh->nh_common.nhc_pcpu_rth_output = NULL;
 		fib6_nh->fib_nh_lws = NULL;
 		netdev_put(dev, dev_tracker);
 	}