af_unix: Reuse out_pipe label in unix_stream_sendmsg().

This is a follow-up of commit d460b04 ("af_unix: Clean up
error paths in unix_stream_sendmsg().").

If we initialise skb with NULL in unix_stream_sendmsg(), we can
reuse the existing out_pipe label for the SEND_SHUTDOWN check.

Let's rename it and adjust the existing label as out_pipe_lock.

While at it, size and data_len are moved to the while loop scope.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250116053441.5758-9-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/unix/af_unix.c

@@ -2238,13 +2238,11 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 			       size_t len)
 {
 	struct sock *sk = sock->sk;
+	struct sk_buff *skb = NULL;
 	struct sock *other = NULL;
-	int err, size;
-	struct sk_buff *skb;
-	int sent = 0;
 	struct scm_cookie scm;
 	bool fds_sent = false;
-	int data_len;
+	int err, sent = 0;
 
 	err = scm_send(sock, msg, &scm, false);
 	if (err < 0)
@@ -2273,16 +2271,12 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 		}
 	}
 
-	if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) {
-		if (!(msg->msg_flags & MSG_NOSIGNAL))
-			send_sig(SIGPIPE, current, 0);
-
-		err = -EPIPE;
-		goto out_err;
-	}
+	if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
+		goto out_pipe;
 
 	while (sent < len) {
-		size = len - sent;
+		int size = len - sent;
+		int data_len;
 
 		if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) {
 			skb = sock_alloc_send_pskb(sk, 0, 0,
@@ -2335,7 +2329,7 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 
 		if (sock_flag(other, SOCK_DEAD) ||
 		    (other->sk_shutdown & RCV_SHUTDOWN))
-			goto out_pipe;
+			goto out_pipe_unlock;
 
 		maybe_add_creds(skb, sock, other);
 		scm_stat_add(other, skb);
@@ -2358,8 +2352,9 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 
 	return sent;
 
-out_pipe:
+out_pipe_unlock:
 	unix_state_unlock(other);
+out_pipe:
 	if (!sent && !(msg->msg_flags & MSG_NOSIGNAL))
 		send_sig(SIGPIPE, current, 0);
 	err = -EPIPE;