net: sock: fix in-kernel mark setting

This patch fixes the in-kernel mark setting by doing an additional
sk_dst_reset() which was introduced by commit 50254256 ("sock: Reset
dst when changing sk_mark via setsockopt"). The code is now shared to
avoid any further suprises when changing the socket mark value.

Fixes: 84d1c617 ("net: sock: add sock_set_mark")
Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -815,10 +815,18 @@ void sock_set_rcvbuf(struct sock *sk, int val)
 }
 EXPORT_SYMBOL(sock_set_rcvbuf);
 
+static void __sock_set_mark(struct sock *sk, u32 val)
+{
+	if (val != sk->sk_mark) {
+		sk->sk_mark = val;
+		sk_dst_reset(sk);
+	}
+}
+
 void sock_set_mark(struct sock *sk, u32 val)
 {
 	lock_sock(sk);
-	sk->sk_mark = val;
+	__sock_set_mark(sk, val);
 	release_sock(sk);
 }
 EXPORT_SYMBOL(sock_set_mark);
@@ -1126,10 +1134,10 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 	case SO_MARK:
 		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
 			ret = -EPERM;
-		} else if (val != sk->sk_mark) {
-			sk->sk_mark = val;
-			sk_dst_reset(sk);
+			break;
 		}
+
+		__sock_set_mark(sk, val);
 		break;
 
 	case SO_RXQ_OVFL: