[PATCH v4 net-next 1/9] af_unix: Factorise test_bit() for SOCK_PASSCRED and SOCK_PASSPIDFD.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

Currently, the same checks for SOCK_PASSCRED and SOCK_PASSPIDFD
are scattered across many places.

Let's centralise the bit tests to make the following changes cleaner.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/unix/af_unix.c | 37 +++++++++++++++----------------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 2ab20821d6bb..464e183ffdb8 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -765,6 +765,14 @@ static void copy_peercred(struct sock *sk, struct sock *peersk)
 	spin_unlock(&sk->sk_peer_lock);
 }
 
+static bool unix_may_passcred(const struct sock *sk)
+{
+	struct socket *sock = sk->sk_socket;
+
+	return test_bit(SOCK_PASSCRED, &sock->flags) ||
+		test_bit(SOCK_PASSPIDFD, &sock->flags);
+}
+
 static int unix_listen(struct socket *sock, int backlog)
 {
 	int err;
@@ -1411,9 +1419,7 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 		if (err)
 			goto out;
 
-		if ((test_bit(SOCK_PASSCRED, &sock->flags) ||
-		     test_bit(SOCK_PASSPIDFD, &sock->flags)) &&
-		    !READ_ONCE(unix_sk(sk)->addr)) {
+		if (unix_may_passcred(sk) && !READ_ONCE(unix_sk(sk)->addr)) {
 			err = unix_autobind(sk);
 			if (err)
 				goto out;
@@ -1531,9 +1537,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	if (err)
 		goto out;
 
-	if ((test_bit(SOCK_PASSCRED, &sock->flags) ||
-	     test_bit(SOCK_PASSPIDFD, &sock->flags)) &&
-	    !READ_ONCE(u->addr)) {
+	if (unix_may_passcred(sk) && !READ_ONCE(u->addr)) {
 		err = unix_autobind(sk);
 		if (err)
 			goto out;
@@ -1877,16 +1881,6 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen
 	return err;
 }
 
-static bool unix_passcred_enabled(const struct socket *sock,
-				  const struct sock *other)
-{
-	return test_bit(SOCK_PASSCRED, &sock->flags) ||
-	       test_bit(SOCK_PASSPIDFD, &sock->flags) ||
-	       !other->sk_socket ||
-	       test_bit(SOCK_PASSCRED, &other->sk_socket->flags) ||
-	       test_bit(SOCK_PASSPIDFD, &other->sk_socket->flags);
-}
-
 /*
  * Some apps rely on write() giving SCM_CREDENTIALS
  * We include credentials if source or destination socket
@@ -1897,7 +1891,9 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
 {
 	if (UNIXCB(skb).pid)
 		return;
-	if (unix_passcred_enabled(sock, other)) {
+
+	if (unix_may_passcred(sock->sk) ||
+	    !other->sk_socket || unix_may_passcred(other)) {
 		UNIXCB(skb).pid  = get_pid(task_tgid(current));
 		current_uid_gid(&UNIXCB(skb).uid, &UNIXCB(skb).gid);
 	}
@@ -1974,9 +1970,7 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
 			goto out;
 	}
 
-	if ((test_bit(SOCK_PASSCRED, &sock->flags) ||
-	     test_bit(SOCK_PASSPIDFD, &sock->flags)) &&
-	    !READ_ONCE(u->addr)) {
+	if (unix_may_passcred(sk) && !READ_ONCE(u->addr)) {
 		err = unix_autobind(sk);
 		if (err)
 			goto out;
@@ -2846,8 +2840,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state,
 			/* Never glue messages from different writers */
 			if (!unix_skb_scm_eq(skb, &scm))
 				break;
-		} else if (test_bit(SOCK_PASSCRED, &sock->flags) ||
-			   test_bit(SOCK_PASSPIDFD, &sock->flags)) {
+		} else if (unix_may_passcred(sk)) {
 			/* Copy credentials */
 			scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
 			unix_set_secdata(&scm, skb);
-- 
2.49.0