net: introduce lockdep_is_held and update various places to use it

The socket is either locked if we hold the slock spin_lock for
lock_sock_fast and unlock_sock_fast or we own the lock (sk_lock.owned
!= 0). Check for this and at the same time improve that the current
thread/cpu is really holding the lock.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 456ff3d..f4f2a0a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -157,7 +157,7 @@
 
 	nexthop = daddr = usin->sin_addr.s_addr;
 	inet_opt = rcu_dereference_protected(inet->inet_opt,
-					     sock_owned_by_user(sk));
+					     lockdep_sock_is_held(sk));
 	if (inet_opt && inet_opt->opt.srr) {
 		if (!daddr)
 			return -EINVAL;
@@ -882,8 +882,7 @@
 
 	/* caller either holds rcu_read_lock() or socket lock */
 	md5sig = rcu_dereference_check(tp->md5sig_info,
-				       sock_owned_by_user(sk) ||
-				       lockdep_is_held((spinlock_t *)&sk->sk_lock.slock));
+				       lockdep_sock_is_held(sk));
 	if (!md5sig)
 		return NULL;
 #if IS_ENABLED(CONFIG_IPV6)
@@ -928,8 +927,7 @@
 	}
 
 	md5sig = rcu_dereference_protected(tp->md5sig_info,
-					   sock_owned_by_user(sk) ||
-					   lockdep_is_held(&sk->sk_lock.slock));
+					   lockdep_sock_is_held(sk));
 	if (!md5sig) {
 		md5sig = kmalloc(sizeof(*md5sig), gfp);
 		if (!md5sig)